Amplify has re-imagined the way frontend developers build fullstack applications. Develop and deploy without the hassle.

Page updated May 21, 2024

Upload files

Implement upload functionality

Note: Refer to the Transfer Acceleration documentation to learn how to enable transfer acceleration for storage APIs.

Upload from file

When you have a file that you want to upload, you can specify the url to the file in the local parameter. If a file with the same path already exists in S3, the existing S3 file will be overwritten.

let dataString = "My Data"
let fileName = "myFile.txt"
guard let fileUrl = FileManager.default.urls(
for: .documentDirectory,
in: .userDomainMask
else { return }
try dataString.write(
to: fileUrl,
atomically: true,
encoding: .utf8
let uploadTask = Amplify.Storage.uploadFile(
path: .fromString("public/example/path/myFile.txt"),
local: filename

Upload from data

To upload a file from a data object, specify the path and the data object to be uploaded.

let dataString = "My Data"
let data = Data(dataString.utf8)
let uploadTask = Amplify.Storage.uploadData(
path: .fromString("public/example/path"),
data: data

Monitor upload progress

To track progress of the upload, use the reference returned by the uploadFile or uploadData as shown below.

Task {
for await progress in await uploadTask.progress {
print("Progress: \(progress)")
let value = try await uploadTask.value
print("Completed: \(value)")
let progressSink = uploadTask
.sink { progress in
print("Progress: \(progress)")
let resultSink = uploadTask
.sink {
if case let .failure(storageError) = $0 {
print("Failed: \(storageError.errorDescription). \(storageError.recoverySuggestion)")
receiveValue: { data in
print("Completed: \(data)")

Pause, resume, and cancel uploads

Calls to uploadData or uploadFile return a reference to the task that is actually performing the upload.

You can pause then resume the task or cancel a task as shown below.


Upload tasks are run using URLSessionTask instances internally. You can learn more about them in Apple's official documentation.

More upload options

metadataDictionaryMetadata for the object to store.
contentTypeStringThe standard MIME type describing the format of the object to store.

Working with Security Scoped Resources (from iCloud)

Security scoped resources refer to files that are retrieved from iCloud or other cloud storage providers. You're likely to run into these file types when using system components that provide access to files stored in iCloud, e.g. UIDocumentBrowserViewController.

To upload security scoped resources, you'll need to:

  1. use startAccessingSecurityScopedResource() and stopAccessingSecurityScopedResource() to access the data within security scoped files
  2. temporarily persist the data from the security scoped files in your app's sandbox
  3. upload files using the temporary URLs
  4. delete temporarily persisted files (optional)
struct ScopedResourceFile {
let name: String
let data: Data
func getTempUrls(securityScopedUrls: [URL]) -> [URL] {
// 1. get the content of security scoped resources into ScopedResourceFile struct
let fileContents = securityScopedUrls.compactMap { url -> ScopedResourceFile? in
let startAccess = url.startAccessingSecurityScopedResource()
guard startAccess else {
print("Issue accessing security scoped resource at :\(url)")
return nil
defer { url.stopAccessingSecurityScopedResource() }
do {
let data = try Data(contentsOf: url)
let fileName = url.lastPathComponent
return ScopedResourceFile(name: fileName, data: data)
} catch {
print("Couldn't create Data from contents of file at url: \(url)")
return nil
// 2. write the file contents to temporary files and return the URLs of the temp files
let localFileURLs = persistTemporaryFiles(fileContents)
// 3. Now you have local URLs for the files you'd like to upload.
return localFileURLs

MultiPart upload

Amplify will automatically perform an Amazon S3 multipart upload for objects that are larger than 5MB. For more information about S3's multipart upload, see Uploading and copying objects using multipart upload