diff --git a/backend/seafile/api/types.go b/backend/seafile/api/types.go
index d6224709f..9dc52deec 100644
--- a/backend/seafile/api/types.go
+++ b/backend/seafile/api/types.go
@@ -26,7 +26,8 @@ type AccountInfo struct {
 
 // ServerInfo contains server information
 type ServerInfo struct {
-	Version string `json:"version"`
+	Version  string   `json:"version"`
+	Features []string `json:"features"`
 }
 
 // DefaultLibrary when none specified
@@ -152,3 +153,13 @@ type BatchSourceDestRequest struct {
 	DstLibraryID string   `json:"dst_repo_id"`
 	DstParentDir string   `json:"dst_parent_dir"`
 }
+
+// FileUploadedBytes contains the JSON response to the "file-uploaded-bytes" API call
+type FileUploadedBytes struct {
+	FileUploadedBytes int64 `json:"uploadedBytes"`
+}
+
+// ChunkUpload contains the result of uploading one part of a file
+type ChunkUpload struct {
+	Success bool `json:"success"`
+}
diff --git a/backend/seafile/content_range.go b/backend/seafile/content_range.go
new file mode 100644
index 000000000..03bf7d248
--- /dev/null
+++ b/backend/seafile/content_range.go
@@ -0,0 +1,71 @@
+package seafile
+
+import "fmt"
+
+type contentRanger interface {
+	getChunkSize() int64
+	getContentRangeHeader() string
+}
+
+type streamedContentRange struct {
+	size int64
+}
+
+func newStreamedContentRange(size int64) *streamedContentRange {
+	return &streamedContentRange{
+		size: size,
+	}
+}
+func (r *streamedContentRange) getChunkSize() int64           { return r.size }
+func (r *streamedContentRange) getContentRangeHeader() string { return "" }
+
+type chunkedContentRange struct {
+	start     int64
+	chunkSize int64
+	size      int64
+}
+
+// newChunkedContentRange does not support streaming (unknown size)
+func newChunkedContentRange(chunkSize, size int64) *chunkedContentRange {
+	if size <= 0 {
+		panic("content range cannot operate on streaming")
+	}
+	if chunkSize <= 0 {
+		panic("content range cannot operate without a chunk size")
+	}
+	return &chunkedContentRange{
+		start:     0,
+		chunkSize: chunkSize,
+		size:      size,
+	}
+}
+
+func (r *chunkedContentRange) getEnd() int64 {
+	end := r.chunkSize + r.start
+	if end > r.size {
+		end = r.size
+	}
+	return end
+}
+
+func (r *chunkedContentRange) getChunkSize() int64 {
+	return r.getEnd() - r.start
+}
+
+// next moves the range to the next frame
+// it panics if it was the last chunk
+func (r *chunkedContentRange) next() {
+	r.start += r.chunkSize
+	if r.start >= r.size {
+		panic("no more chunk of data")
+	}
+}
+
+func (r *chunkedContentRange) isLastChunk() bool {
+	return r.getEnd() == r.size
+}
+
+func (r *chunkedContentRange) getContentRangeHeader() string {
+	end := r.getEnd()
+	return fmt.Sprintf("bytes %d-%d/%d", r.start, end-1, r.size)
+}
diff --git a/backend/seafile/content_range_test.go b/backend/seafile/content_range_test.go
new file mode 100644
index 000000000..92f4373e2
--- /dev/null
+++ b/backend/seafile/content_range_test.go
@@ -0,0 +1,86 @@
+package seafile
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestContentRangeHeader(t *testing.T) {
+	fixtures := []struct {
+		start, chunkSize, size int64
+		expect                 string
+	}{
+		{0, 1, 10, "bytes 0-0/10"}, // from byte 0 (inclusive) to byte 0 (inclusive) == 1 byte
+		{0, 10, 10, "bytes 0-9/10"},
+		{0, 20, 10, "bytes 0-9/10"},
+		{1, 1, 10, "bytes 1-1/10"},
+		{1, 10, 10, "bytes 1-9/10"},
+		{1, 10, 10, "bytes 1-9/10"},
+		{9, 1, 10, "bytes 9-9/10"},
+		{9, 2, 10, "bytes 9-9/10"},
+		{9, 5, 10, "bytes 9-9/10"},
+	}
+
+	for _, fixture := range fixtures {
+		t.Run(fmt.Sprintf("%+v", fixture), func(t *testing.T) {
+			r := &chunkedContentRange{start: fixture.start, chunkSize: fixture.chunkSize, size: fixture.size}
+			assert.Equal(t, fixture.expect, r.getContentRangeHeader())
+		})
+	}
+}
+
+func TestChunkSize(t *testing.T) {
+	fixtures := []struct {
+		start, chunkSize, size int64
+		expected               int64
+		isLastChunk            bool
+	}{
+		{0, 10, 10, 10, true},  // chunk size same as size
+		{0, 20, 10, 10, true},  // chuck size bigger than size
+		{0, 10, 20, 10, false}, // chuck size smaller than size
+		{1, 10, 10, 9, true},   // chunk size same as size
+		{1, 20, 10, 9, true},   // chuck size bigger than size
+		{1, 10, 20, 10, false}, // chuck size smaller than size
+		{15, 10, 20, 5, true},  // smaller remaining
+	}
+
+	for _, fixture := range fixtures {
+		t.Run(fmt.Sprintf("%d/%d/%d", fixture.start, fixture.chunkSize, fixture.size), func(t *testing.T) {
+			r := &chunkedContentRange{start: fixture.start, chunkSize: fixture.chunkSize, size: fixture.size}
+			assert.Equal(t, fixture.expected, r.getChunkSize())
+			assert.Equal(t, fixture.isLastChunk, r.isLastChunk())
+		})
+	}
+}
+
+func TestRanges(t *testing.T) {
+	fixtures := []struct {
+		size           int64
+		chunkSize      int64
+		expectedChunks int
+	}{
+		{10, 1, 10},
+		{20, 2, 10},
+		{10, 10, 1},
+		{10, 3, 4},
+	}
+	for _, fixture := range fixtures {
+		t.Run(fmt.Sprintf("%d/%d", fixture.size, fixture.chunkSize), func(t *testing.T) {
+			r := newChunkedContentRange(fixture.chunkSize, fixture.size)
+			// first chunk is counted before the loop
+			count := 1
+			size := r.getChunkSize()
+
+			for !r.isLastChunk() {
+				r.next()
+				count++
+				size += r.getChunkSize()
+			}
+			assert.Panics(t, func() { r.next() })
+			assert.Equal(t, fixture.expectedChunks, count)
+			assert.Equal(t, fixture.size, size)
+		})
+	}
+}
diff --git a/backend/seafile/object.go b/backend/seafile/object.go
index 25257825a..91b39e786 100644
--- a/backend/seafile/object.go
+++ b/backend/seafile/object.go
@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/rclone/rclone/fs"
+	"github.com/rclone/rclone/fs/chunksize"
 	"github.com/rclone/rclone/fs/hash"
 )
 
@@ -89,29 +90,63 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (io.ReadClo
 // But for unknown-sized objects (indicated by src.Size() == -1), Upload should either
 // return an error or update the object properly (rather than e.g. calling panic).
 func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) error {
-	// The upload sometimes return a temporary 500 error
-	// We cannot use the pacer to retry uploading the file as the upload link is single use only
-	for retry := 0; retry <= 3; retry++ {
-		uploadLink, err := o.fs.getUploadLink(ctx, o.libraryID)
-		if err != nil {
-			return err
-		}
-
-		uploaded, err := o.fs.upload(ctx, in, uploadLink, o.pathInLibrary)
-		if err == ErrorInternalDuringUpload {
-			// This is a temporary error, try again with a new upload link
-			continue
-		}
-		if err != nil {
-			return err
-		}
-		// Set the properties from the upload back to the object
-		o.size = uploaded.Size
-		o.id = uploaded.ID
-
-		return nil
+	size := src.Size()
+	if size <= int64(o.fs.opt.UploadCutoff) || o.fs.noChunkUpload {
+		// upload whole file in 1 request
+		return o.upload(ctx, in, src)
 	}
-	return ErrorInternalDuringUpload
+	// upload in parts
+	chunkSize := chunksize.Calculator(o, size, maxParts, o.fs.opt.ChunkSize)
+	return o.uploadLargeFile(ctx, in, src, chunkSize)
+}
+
+// upload whole file in 1 request
+func (o *Object) upload(ctx context.Context, in io.Reader, src fs.ObjectInfo) error {
+	uploadLink, err := o.fs.getUploadLink(ctx, o.libraryID)
+	if err != nil {
+		return err
+	}
+
+	uploaded, err := o.fs.upload(ctx, in, uploadLink, o.pathInLibrary, src.Size())
+	if err != nil {
+		return err
+	}
+	// Set the properties from the upload back to the object
+	o.size = uploaded.Size
+	o.id = uploaded.ID
+
+	return nil
+}
+
+func (o *Object) uploadLargeFile(ctx context.Context, in io.Reader, src fs.ObjectInfo, chunkSize fs.SizeSuffix) error {
+	uploadLink, err := o.fs.getUploadLink(ctx, o.libraryID)
+	if err != nil {
+		return err
+	}
+	size := src.Size()
+	contentRange := newChunkedContentRange(int64(chunkSize), size)
+	for {
+		fs.Debugf(nil, "uploading chunk %s", contentRange.getContentRangeHeader())
+		err = o.fs.uploadChunk(ctx, in, uploadLink, o.pathInLibrary, contentRange)
+		if err != nil {
+			return err
+		}
+		contentRange.next()
+		// the last part is a slightly different API call
+		if contentRange.isLastChunk() {
+			break
+		}
+	}
+	fs.Debugf(nil, "uploading last chunk %s", contentRange.getContentRangeHeader())
+	uploaded, err := o.fs.uploadLastChunk(ctx, in, uploadLink, o.pathInLibrary, contentRange)
+	if err != nil {
+		return err
+	}
+	// Set the properties from the upload back to the object
+	o.size = uploaded.Size
+	o.id = uploaded.ID
+
+	return nil
 }
 
 // Remove this object
diff --git a/backend/seafile/pacer.go b/backend/seafile/pacer.go
index 55680193e..109955a80 100644
--- a/backend/seafile/pacer.go
+++ b/backend/seafile/pacer.go
@@ -12,9 +12,9 @@ import (
 )
 
 const (
-	minSleep      = 100 * time.Millisecond
-	maxSleep      = 10 * time.Second
-	decayConstant = 2 // bigger for slower decay, exponential
+	defaultMinSleep = 100 * time.Millisecond
+	maxSleep        = 10 * time.Second
+	decayConstant   = 2 // bigger for slower decay, exponential
 )
 
 // Use only one pacer per server URL
@@ -28,7 +28,7 @@ func init() {
 }
 
 // getPacer returns the unique pacer for that remote URL
-func getPacer(ctx context.Context, remote string) *fs.Pacer {
+func getPacer(ctx context.Context, remote string, minPacer int) *fs.Pacer {
 	pacerMutex.Lock()
 	defer pacerMutex.Unlock()
 
@@ -37,6 +37,10 @@ func getPacer(ctx context.Context, remote string) *fs.Pacer {
 		return existing
 	}
 
+	minSleep := time.Duration(minPacer) * time.Millisecond
+	if minSleep == 0 {
+		minSleep = defaultMinSleep
+	}
 	pacers[remote] = fs.NewPacer(
 		ctx,
 		pacer.NewDefault(
diff --git a/backend/seafile/seafile.go b/backend/seafile/seafile.go
index b38dfa2b5..485d3f07e 100644
--- a/backend/seafile/seafile.go
+++ b/backend/seafile/seafile.go
@@ -28,6 +28,7 @@ import (
 	"github.com/rclone/rclone/lib/cache"
 	"github.com/rclone/rclone/lib/encoder"
 	"github.com/rclone/rclone/lib/pacer"
+	"github.com/rclone/rclone/lib/pool"
 	"github.com/rclone/rclone/lib/random"
 	"github.com/rclone/rclone/lib/rest"
 )
@@ -43,6 +44,12 @@ const (
 	configLibraryKey    = "library_key"
 	configCreateLibrary = "create_library"
 	configAuthToken     = "auth_token"
+	minChunkSize        = 1 * fs.Mebi
+	defaultChunkSize    = 127 * fs.Mebi
+	maxChunkSize        = 511 * fs.Mebi
+	defaultUploadCutoff = 255 * fs.Mebi
+	maxParts            = 100000
+	minPacer            = 100
 )
 
 // This is global to all instances of fs
@@ -59,60 +66,92 @@ func init() {
 		Description: "seafile",
 		NewFs:       NewFs,
 		Config:      Config,
-		Options: []fs.Option{{
-			Name:     configURL,
-			Help:     "URL of seafile host to connect to.",
-			Required: true,
-			Examples: []fs.OptionExample{{
-				Value: "https://cloud.seafile.com/",
-				Help:  "Connect to cloud.seafile.com.",
-			}},
-			Sensitive: true,
-		}, {
-			Name:      configUser,
-			Help:      "User name (usually email address).",
-			Required:  true,
-			Sensitive: true,
-		}, {
-			// Password is not required, it will be left blank for 2FA
-			Name:       configPassword,
-			Help:       "Password.",
-			IsPassword: true,
-			Sensitive:  true,
-		}, {
-			Name:    config2FA,
-			Help:    "Two-factor authentication ('true' if the account has 2FA enabled).",
-			Default: false,
-		}, {
-			Name: configLibrary,
-			Help: "Name of the library.\n\nLeave blank to access all non-encrypted libraries.",
-		}, {
-			Name:       configLibraryKey,
-			Help:       "Library password (for encrypted libraries only).\n\nLeave blank if you pass it through the command line.",
-			IsPassword: true,
-			Sensitive:  true,
-		}, {
-			Name:     configCreateLibrary,
-			Help:     "Should rclone create a library if it doesn't exist.",
-			Advanced: true,
-			Default:  false,
-		}, {
-			// Keep the authentication token after entering the 2FA code
-			Name:      configAuthToken,
-			Help:      "Authentication token.",
-			Hide:      fs.OptionHideBoth,
-			Sensitive: true,
-		}, {
-			Name:     config.ConfigEncoding,
-			Help:     config.ConfigEncodingHelp,
-			Advanced: true,
-			Default: (encoder.EncodeZero |
-				encoder.EncodeCtl |
-				encoder.EncodeSlash |
-				encoder.EncodeBackSlash |
-				encoder.EncodeDoubleQuote |
-				encoder.EncodeInvalidUtf8),
-		}},
+		Options: []fs.Option{
+			{
+				Name:     configURL,
+				Help:     "URL of seafile host to connect to.",
+				Required: true,
+				Examples: []fs.OptionExample{{
+					Value: "https://cloud.seafile.com/",
+					Help:  "Connect to cloud.seafile.com.",
+				}},
+				Sensitive: true,
+			}, {
+				Name:      configUser,
+				Help:      "User name (usually email address).",
+				Required:  true,
+				Sensitive: true,
+			}, {
+				// Password is not required, it will be left blank for 2FA
+				Name:       configPassword,
+				Help:       "Password.",
+				IsPassword: true,
+				Sensitive:  true,
+			}, {
+				Name:    config2FA,
+				Help:    "Two-factor authentication ('true' if the account has 2FA enabled).",
+				Default: false,
+			}, {
+				Name: configLibrary,
+				Help: "Name of the library.\n\nLeave blank to access all non-encrypted libraries.",
+			}, {
+				Name:       configLibraryKey,
+				Help:       "Library password (for encrypted libraries only).\n\nLeave blank if you pass it through the command line.",
+				IsPassword: true,
+				Sensitive:  true,
+			}, {
+				Name:     configCreateLibrary,
+				Help:     "Should rclone create a library if it doesn't exist.",
+				Advanced: true,
+				Default:  false,
+			}, {
+				// Keep the authentication token after entering the 2FA code
+				Name:      configAuthToken,
+				Help:      "Authentication token.",
+				Hide:      fs.OptionHideBoth,
+				Sensitive: true,
+			}, {
+				Name:     config.ConfigEncoding,
+				Help:     config.ConfigEncodingHelp,
+				Advanced: true,
+				Default: (encoder.EncodeZero |
+					encoder.EncodeCtl |
+					encoder.EncodeSlash |
+					encoder.EncodeBackSlash |
+					encoder.EncodeDoubleQuote |
+					encoder.EncodeInvalidUtf8),
+			}, {
+				Name: "upload_cutoff",
+				Help: `Cutoff for switching to chunked upload.
+
+Files above this size will be uploaded in chunks of "--seafile-chunk-size".`,
+				Default:  defaultUploadCutoff,
+				Advanced: true,
+			}, {
+				Name: "chunk_size",
+				Help: `Upload chunk size.
+	
+When uploading large files, chunk the file into this size.
+
+Must fit in memory. These chunks are buffered in memory and there
+might a maximum of "--transfers" chunks in progress at once.
+
+1 MB is the minimum size.`,
+				Default:  defaultChunkSize,
+				Advanced: true,
+			}, {
+				Name: "min_pacer",
+				Help: `Minimum time between requests (in milliseconds).
+	
+Seafile API is rate limited. The default value is to wait at least 100ms between requests.
+
+You can try to tweak the default value but you might trigger the rate limit which will make the request rate slower.
+
+The minimum value is 1ms (0 will default to 100ms)`,
+				Default:  minPacer,
+				Advanced: true,
+			},
+		},
 	})
 }
 
@@ -127,28 +166,34 @@ type Options struct {
 	LibraryKey    string               `config:"library_key"`
 	CreateLibrary bool                 `config:"create_library"`
 	Enc           encoder.MultiEncoder `config:"encoding"`
+	UploadCutoff  fs.SizeSuffix        `config:"upload_cutoff"`
+	ChunkSize     fs.SizeSuffix        `config:"chunk_size"`
+	MinPacer      int                  `config:"min_pacer"`
 }
 
 // Fs represents a remote seafile
 type Fs struct {
-	name                string       // name of this remote
-	root                string       // the path we are working on
-	libraryName         string       // current library
-	encrypted           bool         // Is this an encrypted library
-	rootDirectory       string       // directory part of root (if any)
-	opt                 Options      // parsed options
-	libraries           *cache.Cache // Keep a cache of libraries
-	librariesMutex      sync.Mutex   // Mutex to protect getLibraryID
-	features            *fs.Features // optional features
-	endpoint            *url.URL     // URL of the host
-	endpointURL         string       // endpoint as a string
-	srv                 *rest.Client // the connection to the server
-	pacer               *fs.Pacer    // pacer for API calls
-	authMu              sync.Mutex   // Mutex to protect library decryption
-	createDirMutex      sync.Mutex   // Protect creation of directories
-	useOldDirectoryAPI  bool         // Use the old API v2 if seafile < 7
-	moveDirNotAvailable bool         // Version < 7.0 don't have an API to move a directory
-	renew               *Renew       // Renew an encrypted library token
+	name                string         // name of this remote
+	root                string         // the path we are working on
+	libraryName         string         // current library
+	encrypted           bool           // Is this an encrypted library
+	rootDirectory       string         // directory part of root (if any)
+	ci                  *fs.ConfigInfo // global options
+	opt                 Options        // parsed options
+	libraries           *cache.Cache   // Keep a cache of libraries
+	librariesMutex      sync.Mutex     // Mutex to protect getLibraryID
+	features            *fs.Features   // optional features
+	endpoint            *url.URL       // URL of the host
+	endpointURL         string         // endpoint as a string
+	srv                 *rest.Client   // the connection to the server
+	pacer               *fs.Pacer      // pacer for API calls
+	authMu              sync.Mutex     // Mutex to protect library decryption
+	createDirMutex      sync.Mutex     // Protect creation of directories
+	useOldDirectoryAPI  bool           // Use the old API v2 if seafile < 7
+	moveDirNotAvailable bool           // Version < 7.0 don't have an API to move a directory
+	noChunkUpload       bool           // Version < 7.0 don't have support for chunk upload
+	renew               *Renew         // Renew an encrypted library token
+	pool                *pool.Pool     // memory pool
 }
 
 // ------------------------------------------------------------
@@ -195,17 +240,26 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 		return nil, err
 	}
 
+	ci := fs.GetConfig(ctx)
+
 	f := &Fs{
 		name:          name,
 		root:          root,
 		libraryName:   libraryName,
 		rootDirectory: rootDirectory,
 		libraries:     cache.New(),
+		ci:            ci,
 		opt:           *opt,
 		endpoint:      u,
 		endpointURL:   u.String(),
 		srv:           rest.NewClient(fshttp.NewClient(ctx)).SetRoot(u.String()),
-		pacer:         getPacer(ctx, opt.URL),
+		pacer:         getPacer(ctx, opt.URL, opt.MinPacer),
+		pool: pool.New(
+			time.Minute,
+			int(opt.ChunkSize),
+			ci.Transfers,
+			ci.UseMmap,
+		),
 	}
 	f.features = (&fs.Features{
 		CanHaveEmptyDirectories: true,
@@ -216,7 +270,14 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 	if err != nil {
 		return nil, err
 	}
-	fs.Debugf(nil, "Seafile server version %s", serverInfo.Version)
+	edition := "Community"
+	for _, feature := range serverInfo.Features {
+		if feature == "seafile-pro" {
+			edition = "Professional"
+			break
+		}
+	}
+	fs.Debugf(nil, "Seafile server version %s %s Edition", serverInfo.Version, edition)
 
 	// We don't support lower than seafile v6.0 (version 6.0 is already more than 3 years old)
 	serverVersion := semver.New(serverInfo.Version)
@@ -227,8 +288,10 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 		// Seafile 6 does not support recursive listing
 		f.useOldDirectoryAPI = true
 		f.features.ListR = nil
-		// It also does no support moving directories
+		// It also does not support moving directories
 		f.moveDirNotAvailable = true
+		// no chunk upload either
+		f.noChunkUpload = true
 	}
 
 	// Take the authentication token from the configuration first
@@ -1343,6 +1406,57 @@ func (f *Fs) newObject(ctx context.Context, remote string, size int64, modTime t
 	return object
 }
 
+func checkUploadChunkSize(cs fs.SizeSuffix) error {
+	if cs < minChunkSize {
+		return fmt.Errorf("%s is less than %s", cs, minChunkSize)
+	}
+	return nil
+}
+
+func (f *Fs) setUploadChunkSize(cs fs.SizeSuffix) (old fs.SizeSuffix, err error) {
+	err = checkUploadChunkSize(cs)
+	if err == nil {
+		old, f.opt.ChunkSize = f.opt.ChunkSize, cs
+		// this method is only called before starting an upload
+		// so it should be safe to adjust the memory pool to the new chunk size
+		f.pool.Flush()
+		f.pool = pool.New(
+			time.Minute,
+			int(f.opt.ChunkSize),
+			f.ci.Transfers,
+			f.ci.UseMmap,
+		)
+	}
+	return
+}
+
+func checkUploadCutoff(opt *Options, cs fs.SizeSuffix) error {
+	if cs < opt.ChunkSize {
+		return fmt.Errorf("%v is less than chunk size %v", cs, opt.ChunkSize)
+	}
+	return nil
+}
+
+func (f *Fs) setUploadCutoff(cs fs.SizeSuffix) (old fs.SizeSuffix, err error) {
+	err = checkUploadCutoff(&f.opt, cs)
+	if err == nil {
+		old, f.opt.UploadCutoff = f.opt.UploadCutoff, cs
+	}
+	return
+}
+
+func (f *Fs) getBuf(size int) []byte {
+	buf := f.pool.Get()
+	if size > 0 && len(buf) > size {
+		buf = buf[:size]
+	}
+	return buf
+}
+
+func (f *Fs) putBuf(buf []byte) {
+	f.pool.Put(buf)
+}
+
 // Check the interfaces are satisfied
 var (
 	_ fs.Fs           = &Fs{}
diff --git a/backend/seafile/seafile_mock_server_test.go b/backend/seafile/seafile_mock_server_test.go
new file mode 100644
index 000000000..b07bc4a82
--- /dev/null
+++ b/backend/seafile/seafile_mock_server_test.go
@@ -0,0 +1,307 @@
+package seafile
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"fmt"
+	"hash"
+	"io"
+	"mime"
+	"mime/multipart"
+	"net/http"
+	"net/http/httptest"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/rclone/rclone/fs"
+	"github.com/rclone/rclone/fs/config/configmap"
+	"github.com/rclone/rclone/fs/object"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	smallContent = []byte("01234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+)
+
+func getBasicHandler(t *testing.T, libraryID, libraryName string) *http.ServeMux {
+	t.Helper()
+
+	handler := http.NewServeMux()
+	handler.HandleFunc("/api2/server-info/", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(`{"version":"9.0.10"}`))
+	})
+	handler.HandleFunc("/api2/auth-token/", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(`{"token":"test_token"}`))
+	})
+	handler.HandleFunc("/api2/repos/", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(fmt.Sprintf(`[{"encrypted":false,"id":"%s","size":10,"name":"%s"}]`, libraryID, libraryName)))
+	})
+	handler.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		t.Logf("unhandled call to %q", r.URL.String())
+		w.WriteHeader(http.StatusNotFound)
+		_, _ = w.Write([]byte("Not found: " + r.URL.String()))
+	})
+	return handler
+}
+
+func TestNewFsWithMockServer(t *testing.T) {
+	t.Parallel()
+
+	handler := getBasicHandler(t, "library_id", "My Library")
+	server := httptest.NewServer(handler)
+	defer server.Close()
+
+	options := configmap.Simple{
+		"url":     server.URL,
+		"library": "My Library",
+	}
+	fs, err := NewFs(context.Background(), "TestSeafile", "", options)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, fs)
+}
+
+func TestUploadWholeFileWithErrorNoRetry(t *testing.T) {
+	t.Parallel()
+
+	const filename = "new file.txt"
+
+	handler := getBasicHandler(t, "library_id", "My Library")
+	server := httptest.NewServer(handler)
+	defer server.Close()
+
+	// call to retrieve an upload slot
+	handler.HandleFunc("/api2/repos/library_id/upload-link/", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(fmt.Sprintf(`"%s/upload-api/temp_upload"`, server.URL)))
+	})
+	// upload will fail
+	handler.HandleFunc("/upload-api/temp_upload", func(w http.ResponseWriter, r *http.Request) {
+		defer func() { _ = r.Body.Close() }()
+		w.WriteHeader(http.StatusInternalServerError)
+	})
+
+	options := configmap.Simple{
+		"url":           server.URL,
+		"library":       "My Library",
+		"upload_cutoff": defaultUploadCutoff.String(),
+		"chunk_size":    defaultChunkSize.String(),
+	}
+	fs, err := NewFs(context.Background(), "TestSeafile", "", options)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, fs)
+
+	src := object.NewStaticObjectInfo(filename, time.Now(), int64(len(smallContent)), true, nil, nil)
+	// call should fail
+	in := bytes.NewReader(smallContent)
+	_, err = fs.Put(context.Background(), in, src)
+	assert.Error(t, err)
+}
+
+func TestUploadWholeFile(t *testing.T) {
+	t.Parallel()
+
+	const filename = "new file.txt"
+	const parallelUploadCount = 3
+
+	handler := getBasicHandler(t, "library_id", "My Library")
+	server := httptest.NewServer(handler)
+	t.Cleanup(server.Close)
+
+	// call to retrieve an upload slot
+	handler.HandleFunc("/api2/repos/library_id/upload-link/", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(fmt.Sprintf(`"%s/upload-api/temp_upload"`, server.URL)))
+	})
+	handler.HandleFunc("/upload-api/temp_upload", func(w http.ResponseWriter, r *http.Request) {
+		defer func() { _ = r.Body.Close() }()
+
+		mediaType, params, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
+		assert.NoError(t, err)
+		assert.Equal(t, "multipart/form-data", mediaType)
+		mr := multipart.NewReader(r.Body, params["boundary"])
+		for {
+			p, err := mr.NextPart()
+			if err == io.EOF {
+				return
+			}
+			assert.NoError(t, err)
+			if p.FileName() == filename {
+				body, err := io.ReadAll(p)
+				assert.NoError(t, err)
+				assert.Equal(t, smallContent, body)
+
+				// sends response now
+				_, _ = w.Write([]byte(fmt.Sprintf(`[{"name":"%s","size":%d}]`, filename, len(body))))
+			}
+		}
+	})
+
+	for i := 0; i < parallelUploadCount; i++ {
+		t.Run(fmt.Sprintf("parallel upload file %d", i), func(t *testing.T) {
+			t.Parallel()
+
+			uploadFileContent(t, filename, server.URL, smallContent)
+		})
+	}
+}
+
+func TestUploadFileByChunksWithRetryOnError(t *testing.T) {
+	t.Parallel()
+
+	const filename = "new file.txt"
+	const parallelUploadCount = 3
+	var chunkSize fs.SizeSuffix = 1048576
+	var currentUploadID atomic.Int32
+	chunkCount := make([]atomic.Int32, parallelUploadCount)
+	bytesReceived := make([]atomic.Int32, parallelUploadCount)
+	hashes := make([]hash.Hash, parallelUploadCount)
+	for i := 0; i < parallelUploadCount; i++ {
+		hashes[i] = sha256.New()
+	}
+
+	handler := getBasicHandler(t, "library_id", "My Library")
+	server := httptest.NewServer(handler)
+	t.Cleanup(server.Close)
+
+	// call to retrieve an upload slot
+	handler.HandleFunc("/api2/repos/library_id/upload-link/", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(fmt.Sprintf(`"%s/upload-api/temp_upload/%d"`, server.URL, currentUploadID.Load())))
+		currentUploadID.Add(1)
+	})
+
+	// call to upload chunks
+	handler.HandleFunc("/upload-api/temp_upload/", func(w http.ResponseWriter, r *http.Request) {
+		defer func() { _ = r.Body.Close() }()
+
+		// quick hack to get the file ID from the URL
+		rawFileID := strings.TrimPrefix(r.URL.String(), "/upload-api/temp_upload/")
+		rawFileID = strings.TrimSuffix(rawFileID, "?ret-json=1")
+		fileID, err := strconv.Atoi(rawFileID)
+		require.NoError(t, err)
+
+		currentChunk := chunkCount[fileID].Add(1)
+		if currentChunk == 2 {
+			// simulate an error on the second chunk
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		partLen := 0
+		var totalBytesReceived int32
+		// read all the data
+		mediaType, params, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
+		assert.NoError(t, err)
+		assert.Equal(t, "multipart/form-data", mediaType)
+		mr := multipart.NewReader(r.Body, params["boundary"])
+		for {
+			p, err := mr.NextPart()
+			if err == io.EOF {
+				return
+			}
+			assert.NoError(t, err)
+			if p.FileName() == filename {
+				body, err := io.ReadAll(p)
+				assert.NoError(t, err)
+				partLen = len(body)
+				totalBytesReceived = bytesReceived[fileID].Add(int32(partLen))
+				hashes[fileID].Write(body)
+				break
+			}
+		}
+		t.Logf("file %d: received chunk %d = %d bytes", fileID, currentChunk, totalBytesReceived)
+
+		// check the content-range header
+		contentRange := r.Header.Get("Content-Range")
+		t.Logf("uploaded %s", contentRange)
+		pattern := regexp.MustCompile(`bytes (\d+)-(\d+)\/(\d+)`)
+		match := pattern.FindStringSubmatch(contentRange)
+		if len(match) == 4 {
+			start, err := strconv.Atoi(match[1])
+			assert.NoError(t, err)
+			end, err := strconv.Atoi(match[2])
+			assert.NoError(t, err)
+			size, err := strconv.Atoi(match[3])
+			assert.NoError(t, err)
+
+			// make sure the chunk size is right
+			assert.Equal(t, end-start+1, partLen)
+
+			if end+1 == size {
+				// this was the last chunk
+				_, _ = w.Write([]byte(fmt.Sprintf(`[{"name":"%s","id":"new_file_id","size":%d}]`, filename, totalBytesReceived)))
+				t.Logf("file %d: uploaded hash = %x", fileID, hashes[fileID].Sum(nil))
+				return
+			}
+			if end+1 > size {
+				t.Fatalf("end %d is bigger than size %d", end, size)
+			}
+		}
+		// keep going to the next chunk
+		_, _ = w.Write([]byte(`{"success":true}`))
+	})
+
+	for i := 0; i < parallelUploadCount; i++ {
+		fileID := i // can remove this for go >= 1.22
+		t.Run(fmt.Sprintf("parallel upload file %d", fileID), func(t *testing.T) {
+			t.Parallel()
+
+			dataHash := uploadBigFile(t, filename, server.URL, chunkSize)
+			t.Logf("file %d: uploaded hash = %x", fileID, dataHash)
+		})
+	}
+}
+
+func uploadBigFile(t *testing.T, name, endpoint string, chunkSize fs.SizeSuffix) []byte {
+	options := configmap.Simple{
+		"url":           endpoint,
+		"library":       "My Library",
+		"upload_cutoff": chunkSize.String(),
+		"chunk_size":    chunkSize.String(),
+	}
+	fs, err := NewFs(context.Background(), "TestSeafile", "", options)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, fs)
+
+	// should allow for at least 2 chunks
+	buffer := &bytes.Buffer{}
+	iterations := int(chunkSize) * 2 / len(smallContent)
+	for i := 0; i <= iterations; i++ {
+		buffer.Write(smallContent)
+	}
+
+	// calculate the sha256 hash while uploading
+	sha256Hash := sha256.New()
+	reader := io.TeeReader(buffer, sha256Hash)
+
+	size := int64(buffer.Len())
+	src := object.NewStaticObjectInfo(name, time.Now(), size, true, nil, nil)
+
+	object, err := fs.Put(context.Background(), reader, src)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, object)
+	assert.Equal(t, size, object.Size())
+
+	return sha256Hash.Sum(nil)
+}
+
+func uploadFileContent(t *testing.T, name, endpoint string, content []byte) {
+	options := configmap.Simple{
+		"url":           endpoint,
+		"library":       "My Library",
+		"upload_cutoff": defaultUploadCutoff.String(),
+		"chunk_size":    defaultChunkSize.String(),
+	}
+	fs, err := NewFs(context.Background(), "TestSeafile", "", options)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, fs)
+
+	src := object.NewStaticObjectInfo(name, time.Now(), int64(len(content)), true, nil, nil)
+	in := bytes.NewReader(content)
+	object, err := fs.Put(context.Background(), in, src)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, object)
+	assert.Equal(t, int64(len(content)), object.Size())
+}
diff --git a/backend/seafile/seafile_reverseproxy_test.go b/backend/seafile/seafile_reverseproxy_test.go
new file mode 100644
index 000000000..2b7748a30
--- /dev/null
+++ b/backend/seafile/seafile_reverseproxy_test.go
@@ -0,0 +1,162 @@
+//go:build go1.20
+
+package seafile
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/http/httputil"
+	"net/url"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/rclone/rclone/fs"
+	"github.com/rclone/rclone/fs/config/configmap"
+	"github.com/rclone/rclone/fs/object"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewFsWithProxiedServer(t *testing.T) {
+	// creates a reverse proxy to a local instance of seafile
+	host := "localhost:8088"
+	target, _ := url.Parse("http://" + host)
+	handler := &httputil.ReverseProxy{
+		Rewrite: func(pr *httputil.ProxyRequest) {
+			pr.SetURL(target)
+			pr.Out.Host = host
+			t.Logf("calling %s on %s", pr.Out.Method, pr.Out.URL.String())
+		},
+		ModifyResponse: func(r *http.Response) error {
+			t.Logf("%s response: %s", r.Request.URL.String(), r.Status)
+			return nil
+		},
+	}
+	server := httptest.NewServer(handler)
+	defer server.Close()
+
+	options := configmap.Simple{
+		"url":            server.URL,
+		"library":        "My Library",
+		"user":           "seafile@rclone.org",
+		"pass":           "GYdWLJQb55COZYnO9Zl0GcKc_SYDr0EMVcl6rnZVFxV8zoLPBjJ7NQ",
+		"create_library": "true",
+	}
+	fs, err := NewFs(context.Background(), "TestSeafile", "", options)
+	if err != nil && strings.Contains(err.Error(), "502 Bad Gateway") {
+		t.Skip("cannot contact local seafile instance")
+	}
+	assert.NoError(t, err)
+	assert.NotEmpty(t, fs)
+}
+
+// this test is using a reverse proxy to simulate one broken chunk during an upload
+// a local instance of seafile needs to be started from the script "fstest/testserver/init.d/TestSeafile"
+func TestFailedChunkUploadWithProxiedServer(t *testing.T) {
+	minimumChunks := 3
+	var chunkSize fs.SizeSuffix = 1048576
+
+	// should allow for at least minimumChunks
+	writer := &bytes.Buffer{}
+	iterations := int(chunkSize) * minimumChunks / len(smallContent)
+	for i := 0; i <= iterations; i++ {
+		writer.Write(smallContent)
+	}
+	data := writer.Bytes()
+
+	// each test will fail one chunk from 0 to 3
+	for failedChunk := 0; failedChunk < minimumChunks+1; failedChunk++ {
+		t.Run(strconv.Itoa(failedChunk), func(t *testing.T) {
+			chunkCount := 0
+			var proxyURL []byte
+
+			// creates a reverse proxy to a local instance of seafile
+			host := "127.0.0.1:8088"
+			target, _ := url.Parse("http://" + host)
+			handler := &httputil.ReverseProxy{
+				Rewrite: func(pr *httputil.ProxyRequest) {
+					pr.SetURL(target)
+					pr.Out.Host = host
+					pr.Out.Header.Del("Accept-Encoding") // we don't want to decompress and recompress the response
+					if strings.Contains(pr.Out.URL.String(), "/upload-api/") {
+						t.Logf("uploading chunk %s (%d)", pr.Out.Header.Get("Content-Range"), chunkCount)
+						if chunkCount == failedChunk {
+							t.Logf("this chunk should fail (%d)", chunkCount)
+							// the length of the data won't match with the Content-Length header
+							pr.Out.Body = io.NopCloser(io.LimitReader(pr.In.Body, 100))
+						}
+						chunkCount++
+					}
+				},
+				ModifyResponse: func(r *http.Response) error {
+					b, _ := io.ReadAll(r.Body)
+					_ = r.Body.Close()
+
+					// replace the URLs with the reverse proxy
+					b = bytes.ReplaceAll(b, []byte("http://"+host), proxyURL)
+					buf := bytes.NewBuffer(b)
+					r.Body = io.NopCloser(buf)
+					r.Header.Set("Content-Length", strconv.Itoa(buf.Len()))
+					return nil
+				},
+				ErrorHandler: func(w http.ResponseWriter, r *http.Request, err error) {
+					if strings.Contains(err.Error(), "transport connection broken") {
+						// we need to send a 500 error like the seafile server would do in case of a transmission error
+						w.WriteHeader(http.StatusInternalServerError)
+						return
+					}
+					t.Log(err)
+					w.WriteHeader(http.StatusBadGateway)
+				},
+			}
+			server := httptest.NewServer(handler)
+			defer server.Close()
+			proxyURL = []byte(server.URL)
+
+			options := configmap.Simple{
+				"url":            server.URL,
+				"library":        "My Library",
+				"user":           "seafile@rclone.org",
+				"pass":           "GYdWLJQb55COZYnO9Zl0GcKc_SYDr0EMVcl6rnZVFxV8zoLPBjJ7NQ",
+				"create_library": "true",
+				"upload_cutoff":  chunkSize.String(),
+				"chunk_size":     chunkSize.String(),
+			}
+			fs, err := NewFs(context.Background(), "TestSeafile", "", options)
+			if err != nil && strings.Contains(err.Error(), "502 Bad Gateway") {
+				t.Skip("cannot contact local seafile instance")
+			}
+			assert.NoError(t, err)
+			assert.NotEmpty(t, fs)
+
+			buffer := bytes.NewBuffer(data)
+
+			size := int64(buffer.Len())
+			filename := fmt.Sprintf("new file %d.txt", failedChunk)
+			src := object.NewStaticObjectInfo(filename, time.Now(), size, true, nil, nil)
+
+			object, err := fs.Put(context.Background(), buffer, src)
+			assert.NoError(t, err)
+			assert.NotEmpty(t, object)
+			assert.Equal(t, size, object.Size())
+
+			// read the file back for comparison
+			object, err = fs.NewObject(context.Background(), filename)
+			assert.NoError(t, err)
+			reader, err := object.Open(context.Background())
+			assert.NoError(t, err)
+			read, err := io.ReadAll(reader)
+			assert.NoError(t, err)
+			assert.Equal(t, data, read)
+
+			// clean up
+			err = object.Remove(context.Background())
+			assert.NoError(t, err)
+		})
+	}
+}
diff --git a/backend/seafile/seafile_test.go b/backend/seafile/seafile_test.go
index 669478548..e12fc44c6 100644
--- a/backend/seafile/seafile_test.go
+++ b/backend/seafile/seafile_test.go
@@ -1,10 +1,10 @@
 // Test Seafile filesystem interface
-package seafile_test
+package seafile
 
 import (
 	"testing"
 
-	"github.com/rclone/rclone/backend/seafile"
+	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fstest/fstests"
 )
 
@@ -12,6 +12,24 @@ import (
 func TestIntegration(t *testing.T) {
 	fstests.Run(t, &fstests.Opt{
 		RemoteName: "TestSeafile:",
-		NilObject:  (*seafile.Object)(nil),
+		NilObject:  (*Object)(nil),
+		ChunkedUpload: fstests.ChunkedUploadConfig{
+			MinChunkSize:       minChunkSize,
+			MaxChunkSize:       maxChunkSize,
+			NeedMultipleChunks: true,
+		},
 	})
 }
+
+func (f *Fs) SetUploadChunkSize(cs fs.SizeSuffix) (fs.SizeSuffix, error) {
+	return f.setUploadChunkSize(cs)
+}
+
+func (f *Fs) SetUploadCutoff(cs fs.SizeSuffix) (fs.SizeSuffix, error) {
+	return f.setUploadCutoff(cs)
+}
+
+var (
+	_ fstests.SetUploadChunkSizer = (*Fs)(nil)
+	_ fstests.SetUploadCutoffer   = (*Fs)(nil)
+)
diff --git a/backend/seafile/webapi.go b/backend/seafile/webapi.go
index 1cc05a14b..ed66af3a9 100644
--- a/backend/seafile/webapi.go
+++ b/backend/seafile/webapi.go
@@ -31,14 +31,28 @@ var (
 // ==================== Seafile API ====================
 
 func (f *Fs) getAuthorizationToken(ctx context.Context) (string, error) {
-	return getAuthorizationToken(ctx, f.srv, f.opt.User, f.opt.Password, "")
+	opts, request := prepareAuthorizationRequest(f.opt.User, f.opt.Password, "")
+	result := api.AuthenticationResult{}
+
+	err := f.pacer.Call(func() (bool, error) {
+		resp, err := f.srv.CallJSON(ctx, &opts, &request, &result)
+		return f.shouldRetry(ctx, resp, err)
+	})
+	if err != nil {
+		// This is only going to be http errors here
+		return "", fmt.Errorf("failed to authenticate: %w", err)
+	}
+	if result.Errors != nil && len(result.Errors) > 0 {
+		return "", errors.New(strings.Join(result.Errors, ", "))
+	}
+	if result.Token == "" {
+		// No error in "non_field_errors" field but still empty token
+		return "", errors.New("failed to authenticate")
+	}
+	return result.Token, nil
 }
 
-// getAuthorizationToken can be called outside of an fs (during configuration of the remote to get the authentication token)
-// it's doing a single call (no pacer involved)
-func getAuthorizationToken(ctx context.Context, srv *rest.Client, user, password, oneTimeCode string) (string, error) {
-	// API Documentation
-	// https://download.seafile.com/published/web-api/home.md#user-content-Quick%20Start
+func prepareAuthorizationRequest(user, password, oneTimeCode string) (rest.Opts, api.AuthenticationRequest) {
 	opts := rest.Opts{
 		Method:       "POST",
 		Path:         "api2/auth-token/",
@@ -55,6 +69,15 @@ func getAuthorizationToken(ctx context.Context, srv *rest.Client, user, password
 		Username: user,
 		Password: password,
 	}
+	return opts, request
+}
+
+// getAuthorizationToken is called outside of an fs (during configuration of the remote to get the authentication token)
+// it's doing a single call (no pacer involved)
+func getAuthorizationToken(ctx context.Context, srv *rest.Client, user, password, oneTimeCode string) (string, error) {
+	// API Documentation
+	// https://download.seafile.com/published/web-api/home.md#user-content-Quick%20Start
+	opts, request := prepareAuthorizationRequest(user, password, oneTimeCode)
 	result := api.AuthenticationResult{}
 
 	_, err := srv.CallJSON(ctx, &opts, &request, &result)
@@ -480,6 +503,9 @@ func (f *Fs) deleteDir(ctx context.Context, libraryID, filePath string) error {
 			if resp.StatusCode == 401 || resp.StatusCode == 403 {
 				return fs.ErrorPermissionDenied
 			}
+			if resp.StatusCode == 404 {
+				return fs.ErrorDirNotFound
+			}
 		}
 		return fmt.Errorf("failed to delete directory: %w", err)
 	}
@@ -678,27 +704,76 @@ func (f *Fs) getUploadLink(ctx context.Context, libraryID string) (string, error
 	return result, nil
 }
 
-func (f *Fs) upload(ctx context.Context, in io.Reader, uploadLink, filePath string) (*api.FileDetail, error) {
+// getFileUploadedSize returns the size already uploaded on the server
+//
+//nolint:unused
+func (f *Fs) getFileUploadedSize(ctx context.Context, libraryID, filePath string) (int64, error) {
 	// API Documentation
 	// https://download.seafile.com/published/web-api/v2.1/file-upload.md
+	if libraryID == "" {
+		return 0, errors.New("cannot get file uploaded size without a library")
+	}
+	fs.Debugf(nil, "filePath=%q", filePath)
 	fileDir, filename := path.Split(filePath)
+	fileDir = "/" + strings.TrimSuffix(fileDir, "/")
+	if fileDir == "" {
+		fileDir = "/"
+	}
+	opts := rest.Opts{
+		Method: "GET",
+		Path:   APIv21 + libraryID + "/file-uploaded-bytes/",
+		Parameters: url.Values{
+			"parent_dir": {f.opt.Enc.FromStandardPath(fileDir)},
+			"file_name":  {f.opt.Enc.FromStandardPath(filename)},
+		},
+	}
+
+	result := api.FileUploadedBytes{}
+	var resp *http.Response
+	var err error
+	err = f.pacer.Call(func() (bool, error) {
+		resp, err = f.srv.CallJSON(ctx, &opts, nil, &result)
+		return f.shouldRetry(ctx, resp, err)
+	})
+	if err != nil {
+		if resp != nil {
+			if resp.StatusCode == 401 || resp.StatusCode == 403 {
+				return 0, fs.ErrorPermissionDenied
+			}
+		}
+		return 0, fmt.Errorf("failed to get file uploaded size for parent_dir=%q and file_name=%q: %w", fileDir, filename, err)
+	}
+	return result.FileUploadedBytes, nil
+}
+
+func (f *Fs) prepareFileUpload(ctx context.Context, in io.Reader, uploadLink, filePath string, contentRange contentRanger) (*rest.Opts, error) {
+	fileDir, filename := path.Split(filePath)
+	safeFilename := f.opt.Enc.FromStandardName(filename)
 	parameters := url.Values{
 		"parent_dir":        {"/"},
 		"relative_path":     {f.opt.Enc.FromStandardPath(fileDir)},
 		"need_idx_progress": {"true"},
 		"replace":           {"1"},
 	}
-	formReader, contentType, _, err := rest.MultipartUpload(ctx, in, parameters, "file", f.opt.Enc.FromStandardName(filename))
-	if err != nil {
-		return nil, fmt.Errorf("failed to make multipart upload: %w", err)
+
+	contentRangeHeader := contentRange.getContentRangeHeader()
+	opts := &rest.Opts{
+		Method:               http.MethodPost,
+		Body:                 in,
+		ContentRange:         contentRangeHeader,
+		Parameters:           url.Values{"ret-json": {"1"}}, // It needs to be on the url, not in the body parameters
+		MultipartParams:      parameters,
+		MultipartContentName: "file",
+		MultipartFileName:    safeFilename,
+	}
+	if contentRangeHeader != "" {
+		// When using resumable upload, the name of the file is no longer retrieved from the "file" field of the form.
+		// It's instead retrieved from the header.
+		opts.ExtraHeaders = map[string]string{
+			"Content-Disposition": "attachment; filename=\"" + safeFilename + "\"",
+		}
 	}
 
-	opts := rest.Opts{
-		Method:      "POST",
-		Body:        formReader,
-		ContentType: contentType,
-		Parameters:  url.Values{"ret-json": {"1"}}, // It needs to be on the url, not in the body parameters
-	}
 	parsedURL, err := url.Parse(uploadLink)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse upload url: %w", err)
@@ -708,11 +783,29 @@ func (f *Fs) upload(ctx context.Context, in io.Reader, uploadLink, filePath stri
 	} else {
 		opts.Path = uploadLink
 	}
+
+	chunkSize := contentRange.getChunkSize()
+	if chunkSize > 0 {
+		// seafile might not make use of the Content-Length header but a proxy (or reverse proxy) in the middle might
+		opts.ContentLength = &chunkSize
+	}
+	return opts, nil
+}
+
+func (f *Fs) upload(ctx context.Context, in io.Reader, uploadLink, filePath string, size int64) (*api.FileDetail, error) {
+	// API Documentation
+	// https://download.seafile.com/published/web-api/v2.1/file-upload.md
+	contentRange := newStreamedContentRange(size)
+	opts, err := f.prepareFileUpload(ctx, in, uploadLink, filePath, contentRange)
+	if err != nil {
+		return nil, err
+	}
+
 	result := make([]api.FileDetail, 1)
 	var resp *http.Response
-	// If an error occurs during the call, do not attempt to retry: The upload link is single use only
+	// We do not attempt to retry if an error occurs during the call, as we don't know the state of the reader
 	err = f.pacer.CallNoRetry(func() (bool, error) {
-		resp, err = f.srv.CallJSON(ctx, &opts, nil, &result)
+		resp, err = f.srv.CallJSON(ctx, opts, nil, &result)
 		return f.shouldRetryUpload(ctx, resp, err)
 	})
 	if err != nil {
@@ -721,7 +814,7 @@ func (f *Fs) upload(ctx context.Context, in io.Reader, uploadLink, filePath stri
 				return nil, fs.ErrorPermissionDenied
 			}
 			if resp.StatusCode == 500 {
-				// This is a temporary error - we will get a new upload link before retrying
+				// This is quite common on heavy load
 				return nil, ErrorInternalDuringUpload
 			}
 		}
@@ -732,6 +825,97 @@ func (f *Fs) upload(ctx context.Context, in io.Reader, uploadLink, filePath stri
 		result[0].Name = f.opt.Enc.ToStandardName(result[0].Name)
 		return &result[0], nil
 	}
+	// no file results sent back
+	return nil, ErrorInternalDuringUpload
+}
+
+func (f *Fs) uploadChunk(ctx context.Context, in io.Reader, uploadLink, filePath string, contentRange contentRanger) error {
+	// API Documentation
+	// https://download.seafile.com/published/web-api/v2.1/file-upload.md
+	chunkSize := int(contentRange.getChunkSize())
+	buffer := f.getBuf(chunkSize)
+	defer f.putBuf(buffer)
+
+	read, err := io.ReadFull(in, buffer)
+	if err != nil {
+		return fmt.Errorf("error reading from source: %w", err)
+	}
+	if chunkSize > 0 && read != chunkSize {
+		return fmt.Errorf("expected to read %d from source, but got %d", chunkSize, read)
+	}
+
+	result := api.ChunkUpload{}
+	var resp *http.Response
+	err = f.pacer.Call(func() (bool, error) {
+		// recreate a reader on the temporary buffer
+		in = bytes.NewReader(buffer)
+		opts, err := f.prepareFileUpload(ctx, in, uploadLink, filePath, contentRange)
+		if err != nil {
+			return false, err
+		}
+		resp, err = f.srv.CallJSON(ctx, opts, nil, &result)
+		return f.shouldRetry(ctx, resp, err)
+	})
+	if err != nil {
+		if resp != nil {
+			if resp.StatusCode == 401 || resp.StatusCode == 403 {
+				return fs.ErrorPermissionDenied
+			}
+			if resp.StatusCode == 500 {
+				return fmt.Errorf("chunk upload %s: %w", contentRange.getContentRangeHeader(), ErrorInternalDuringUpload)
+			}
+		}
+		return fmt.Errorf("failed to upload chunk %s: %w", contentRange.getContentRangeHeader(), err)
+	}
+	if !result.Success {
+		return errors.New("upload failed")
+	}
+	return nil
+}
+
+func (f *Fs) uploadLastChunk(ctx context.Context, in io.Reader, uploadLink, filePath string, contentRange contentRanger) (*api.FileDetail, error) {
+	// API Documentation
+	// https://download.seafile.com/published/web-api/v2.1/file-upload.md
+	chunkSize := int(contentRange.getChunkSize())
+	buffer := f.getBuf(chunkSize)
+	defer f.putBuf(buffer)
+
+	read, err := io.ReadFull(in, buffer)
+	if err != nil {
+		return nil, fmt.Errorf("error reading from source: %w", err)
+	}
+	if chunkSize > 0 && read != chunkSize {
+		return nil, fmt.Errorf("expected to read %d from source, but got %d", chunkSize, read)
+	}
+
+	result := make([]api.FileDetail, 1)
+	var resp *http.Response
+	err = f.pacer.Call(func() (bool, error) {
+		// recreate a reader on the buffer
+		in = bytes.NewReader(buffer)
+		opts, err := f.prepareFileUpload(ctx, in, uploadLink, filePath, contentRange)
+		if err != nil {
+			return false, err
+		}
+		resp, err = f.srv.CallJSON(ctx, opts, nil, &result)
+		return f.shouldRetry(ctx, resp, err)
+	})
+	if err != nil {
+		if resp != nil {
+			if resp.StatusCode == 401 || resp.StatusCode == 403 {
+				return nil, fs.ErrorPermissionDenied
+			}
+			if resp.StatusCode == 500 {
+				return nil, fmt.Errorf("last chunk: %w", ErrorInternalDuringUpload)
+			}
+		}
+		return nil, fmt.Errorf("failed to upload last chunk: %w", err)
+	}
+	if len(result) > 0 {
+		result[0].Parent = f.opt.Enc.ToStandardPath(result[0].Parent)
+		result[0].Name = f.opt.Enc.ToStandardName(result[0].Name)
+		return &result[0], nil
+	}
 	return nil, nil
 }
 
diff --git a/docs/content/seafile.md b/docs/content/seafile.md
index a7b32f597..1f909aeb7 100644
--- a/docs/content/seafile.md
+++ b/docs/content/seafile.md
@@ -400,5 +400,53 @@ Properties:
 - Type:        string
 - Required:    false
 
+#### --seafile-upload-cutoff
+
+Cutoff for switching to chunked upload.
+
+Files above this size will be uploaded in chunks of "--seafile-chunk-size".
+
+Properties:
+
+- Config:      upload_cutoff
+- Env Var:     RCLONE_SEAFILE_UPLOAD_CUTOFF
+- Type:        SizeSuffix
+- Default:     255Mi
+
+#### --seafile-chunk-size
+
+Upload chunk size.
+	
+	When uploading large files, chunk the file into this size.
+	
+	Must fit in memory. These chunks are buffered in memory and there
+	might a maximum of "--transfers" chunks in progress at once.
+	
+	1 MB is the minimum size.
+
+Properties:
+
+- Config:      chunk_size
+- Env Var:     RCLONE_SEAFILE_CHUNK_SIZE
+- Type:        SizeSuffix
+- Default:     127Mi
+
+#### --seafile-min-pacer
+
+Minimum time between requests (in milliseconds).
+	
+	Seafile API is rate limited. The default value is to wait at least 100ms between requests.
+	
+	You can try to tweak the default value but you might trigger the rate limit which will make the request rate slower.
+	
+	The minimum value is 1ms (0 will default to 100ms)
+
+Properties:
+
+- Config:      min_pacer
+- Env Var:     RCLONE_SEAFILE_MIN_PACER
+- Type:        int
+- Default:     100
+
 {{< rem autogenerated options stop >}}
 
diff --git a/fstest/test_all/config.yaml b/fstest/test_all/config.yaml
index 10279dd66..569eb30ee 100644
--- a/fstest/test_all/config.yaml
+++ b/fstest/test_all/config.yaml
@@ -418,11 +418,6 @@ backends:
    fastlist: false
    ignore:
      - TestApplyTransforms
- - backend:  "seafile"
-   remote:   "TestSeafileV6:"
-   fastlist: false
-   ignore:
-     - TestIntegration/FsMkdir/FsPutFiles/FsDirMove
  - backend:  "seafile"
    remote:   "TestSeafile:"
    fastlist: true
diff --git a/fstest/testserver/init.d/TestSeafile b/fstest/testserver/init.d/TestSeafile
index c18a1d0db..6fc680902 100755
--- a/fstest/testserver/init.d/TestSeafile
+++ b/fstest/testserver/init.d/TestSeafile
@@ -3,14 +3,14 @@
 set -e
 
 # environment variables passed on docker-compose
-export NAME=seafile7
+export NAME=seafile
 export MYSQL_ROOT_PASSWORD=pixenij4zacoguq0kopamid6
 export SEAFILE_ADMIN_EMAIL=seafile@rclone.org
 export SEAFILE_ADMIN_PASSWORD=pixenij4zacoguq0kopamid6
 export SEAFILE_IP=127.0.0.1
 export SEAFILE_PORT=8087
 export SEAFILE_TEST_DATA=${SEAFILE_TEST_DATA:-/tmp/seafile-test-data}
-export SEAFILE_VERSION=latest
+export SEAFILE_VERSION=${SEAFILE_VERSION:-latest}
 
 # make sure the data directory exists
 mkdir -p ${SEAFILE_TEST_DATA}/${NAME}
@@ -45,12 +45,14 @@ start() {
     # create default library
     curl -X POST -H "Authorization: Token ${TOKEN}" "http://${SEAFILE_IP}:${SEAFILE_PORT}/api2/default-repo/"
 
+    echo
     echo _connect=${SEAFILE_IP}:${SEAFILE_PORT}
     echo type=seafile
     echo url=http://${SEAFILE_IP}:${SEAFILE_PORT}/
     echo user=${SEAFILE_ADMIN_EMAIL}
     echo pass=$(rclone obscure ${SEAFILE_ADMIN_PASSWORD})
     echo library=My Library
+    echo min_pacer=100
 }
 
 stop() {
diff --git a/fstest/testserver/init.d/TestSeafileEncrypted b/fstest/testserver/init.d/TestSeafileEncrypted
index 0493e9082..a4eb2791c 100755
--- a/fstest/testserver/init.d/TestSeafileEncrypted
+++ b/fstest/testserver/init.d/TestSeafileEncrypted
@@ -7,14 +7,14 @@ TEST_LIBRARY=Encrypted
 TEST_LIBRARY_PASSWORD=SecretKey
 
 # environment variables passed on docker-compose
-export NAME=seafile7encrypted
+export NAME=seafile-encrypted
 export MYSQL_ROOT_PASSWORD=pixenij4zacoguq0kopamid6
 export SEAFILE_ADMIN_EMAIL=seafile@rclone.org
 export SEAFILE_ADMIN_PASSWORD=pixenij4zacoguq0kopamid6
 export SEAFILE_IP=127.0.0.1
 export SEAFILE_PORT=8088
 export SEAFILE_TEST_DATA=${SEAFILE_TEST_DATA:-/tmp/seafile-test-data}
-export SEAFILE_VERSION=latest
+export SEAFILE_VERSION=${SEAFILE_VERSION:-latest}
 
 # make sure the data directory exists
 mkdir -p ${SEAFILE_TEST_DATA}/${NAME}
@@ -25,8 +25,20 @@ COMPOSE_DIR=$(dirname "$0")/seafile
 start() {
     docker-compose --project-directory ${COMPOSE_DIR} --project-name ${NAME} --file ${COMPOSE_DIR}/docker-compose.yml up -d
 
-    # it takes some time for the database to be created
-    sleep 60
+    # wait for Seafile server to start
+    seafile_endpoint="http://${SEAFILE_IP}:${SEAFILE_PORT}/"
+    wait_seconds=1
+    echo -n "Waiting for Seafile server to start"
+    for iterations in `seq 1 60`;
+    do
+      http_code=$(curl -s -o /dev/null -L -w '%{http_code}' "$seafile_endpoint" || true;)
+      if [ "$http_code" -eq 200 ]; then
+        echo
+        break
+      fi
+      echo -n "."
+      sleep $wait_seconds
+    done
 
     # authentication token answer should be like: {"token":"dbf58423f1632b5b679a13b0929f1d0751d9250c"}
     TOKEN=`curl --silent \
@@ -37,6 +49,7 @@ start() {
     # create encrypted library
     curl -X POST -d "name=${TEST_LIBRARY}&passwd=${TEST_LIBRARY_PASSWORD}" -H "Authorization: Token ${TOKEN}" "http://${SEAFILE_IP}:${SEAFILE_PORT}/api2/repos/"
 
+    echo
     echo _connect=${SEAFILE_IP}:${SEAFILE_PORT}
     echo type=seafile
     echo url=http://${SEAFILE_IP}:${SEAFILE_PORT}/
@@ -44,6 +57,7 @@ start() {
     echo pass=$(rclone obscure ${SEAFILE_ADMIN_PASSWORD})
     echo library=${TEST_LIBRARY}
     echo library_key=$(rclone obscure ${TEST_LIBRARY_PASSWORD})
+    echo min_pacer=100
 }
 
 stop() {
diff --git a/fstest/testserver/init.d/TestSeafileV6 b/fstest/testserver/init.d/TestSeafileV6
deleted file mode 100755
index 1ed076c44..000000000
--- a/fstest/testserver/init.d/TestSeafileV6
+++ /dev/null
@@ -1,48 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-# local variables
-NAME=seafile6
-SEAFILE_IP=127.0.0.1
-SEAFILE_PORT=8086
-SEAFILE_ADMIN_EMAIL=seafile@rclone.org
-SEAFILE_ADMIN_PASSWORD=qebiwob7wafixif8sojiboj4
-SEAFILE_TEST_DATA=${SEAFILE_TEST_DATA:-/tmp/seafile-test-data}
-SEAFILE_VERSION=latest
-
-. $(dirname "$0")/docker.bash
-
-start() {
-    # make sure the data directory exists
-    mkdir -p ${SEAFILE_TEST_DATA}/${NAME}
-
-    docker run --rm -d --name $NAME \
-        -e SEAFILE_SERVER_HOSTNAME=${SEAFILE_IP}:${SEAFILE_PORT} \
-        -e SEAFILE_ADMIN_EMAIL=${SEAFILE_ADMIN_EMAIL} \
-        -e SEAFILE_ADMIN_PASSWORD=${SEAFILE_ADMIN_PASSWORD} \
-        -v ${SEAFILE_TEST_DATA}/${NAME}:/shared \
-        -p ${SEAFILE_IP}:${SEAFILE_PORT}:80 \
-        seafileltd/seafile:${SEAFILE_VERSION}
-
-    # it takes some time for the database to be created
-    sleep 60
-
-    # authentication token answer should be like: {"token":"dbf58423f1632b5b679a13b0929f1d0751d9250c"}
-    TOKEN=`curl --silent \
-        --data-urlencode username=${SEAFILE_ADMIN_EMAIL} -d password=${SEAFILE_ADMIN_PASSWORD} \
-        http://${SEAFILE_IP}:${SEAFILE_PORT}/api2/auth-token/ \
-        | sed 's/^{"token":"\(.*\)"}$/\1/'`
-
-    # create default library
-    curl -X POST -H "Authorization: Token ${TOKEN}" "http://${SEAFILE_IP}:${SEAFILE_PORT}/api2/default-repo/"
-
-    echo _connect=${SEAFILE_IP}:${SEAFILE_PORT}
-    echo type=seafile
-    echo url=http://${SEAFILE_IP}:${SEAFILE_PORT}/
-    echo user=${SEAFILE_ADMIN_EMAIL}
-    echo pass=$(rclone obscure ${SEAFILE_ADMIN_PASSWORD})
-    echo library=My Library
-}
-
-. $(dirname "$0")/run.bash