Upload & Download

Sairo supports uploading and downloading objects directly through the browser UI.

Upload

Drag and drop

Drag files from your desktop or file manager and drop them anywhere on the object browser. Sairo will upload them to the current folder.

Multi-file batch upload

You can drop multiple files at once or use the upload button to select several files from the file picker. All selected files are uploaded in parallel.

Direct browser-to-S3 upload

Since v3.4.0, uploads go directly from your browser to the S3 endpoint — the file data does not pass through the Sairo server. Sairo only issues short-lived presigned URLs; the bytes flow browser → S3.

• Small files (≤ 100 MB) upload with a single presigned PUT.
• Large files (> 100 MB) use presigned multipart upload: the browser splits the file into parts and uploads them to S3 in parallel, each part signed just-in-time so a long transfer never fails on an expired URL. There is no single-PUT size ceiling — you can upload files far larger than before (up to S3’s 5 TB object limit). A progress bar (with ETA) tracks the whole file, and an in-progress upload can be Stopped, which aborts the multipart upload on S3 so no orphaned parts are left behind.

Because no file data is buffered on the server, large uploads no longer cause memory pressure or pod restarts at scale.

Note

Direct upload requires the bucket’s CORS to allow PUT from the Sairo origin and to expose the ETag response header (the browser must read each part’s ETag). Sairo configures this automatically on providers that support the S3 bucket-CORS API. On providers that don’t (e.g. MinIO, which is configured globally), set CORS to allow PUT/GET from the Sairo origin and expose ETag.

Proxy fallback

If direct upload isn’t available (for example a restricted environment that blocks the browser→S3 request), Sairo falls back to a proxy upload through the server. This path now streams each file straight to S3 instead of buffering it in memory, so peak memory is bounded (~100 MB per in-flight file regardless of file size) rather than growing with the file. Concurrency is controlled by UPLOAD_PROXY_CONCURRENCY (default 3). You can also toggle proxy upload manually with the Direct upload checkbox in the upload dialog.

Note

Incomplete multipart uploads consume storage on the S3 backend. You can track and abort incomplete uploads from the bucket’s Settings > Multipart tab, or configure an AbortIncompleteMultipartUpload lifecycle rule to clean them up automatically.

Download

Presigned URLs

When you download an object, Sairo generates a presigned URL and redirects your browser to it. The file downloads directly from S3 without proxying through the Sairo backend, which keeps downloads fast and avoids putting load on the application server.

Configurable expiration

Presigned download URLs support configurable expiration times:

Option	Expiration
Default	1 hour
Extended	24 hours
Long	7 days

Choose the expiration that fits your use case. Shorter expirations are more secure; longer expirations are convenient when sharing a link that someone may not access immediately.

Tip

For sharing files with people who do not have Sairo accounts, consider using Share Links instead. Share links provide password protection, download limits, and do not require S3 credentials.