An open protocol for resumable file uploads that picks up where it left off if the connection drops.
TUS is an open protocol for resumable file uploads over HTTP. When uploading a large file, if the connection drops — the browser tab closes, Wi-Fi disconnects, or the server hiccups — TUS allows the upload to resume from where it stopped rather than starting over. It is like a bookmark for file transfers: lose your connection at 80%, and you pick up at 80% instead of page one.
TUS works by dividing the upload process into two phases: creation and transfer. First, the client sends a creation request that tells the server about the file (size, type, metadata). The server responds with a unique URL for that upload. Then the client sends the file data in chunks to that URL.
The key innovation is the offset mechanism. After each chunk is uploaded, both the client and server agree on how many bytes have been transferred. If the connection drops, the client sends a HEAD request to the upload URL, and the server responds with the current offset. The client then resumes sending data from that exact byte.
This approach is protocol-level, meaning it works regardless of the application or programming language. TUS clients exist for JavaScript, Python, Go, iOS, Android, and more. The protocol is stateless on the client side — you can close your browser, open it again, and resume the same upload as long as you have the upload URL.
Standard HTTP uploads are all-or-nothing. A 2 GB video file on a shaky connection might fail at 95%, forcing the user to start over. This is not just annoying — it is a real barrier to adoption for platforms that accept large file uploads. Users on mobile connections, in areas with unreliable internet, or uploading very large files need resumability to be productive.
For businesses, TUS reduces upload failures, decreases support tickets, and removes a significant source of frustration from the upload experience.
host.video uses the TUS protocol for all video uploads, providing resumable, reliable transfers regardless of file size or connection quality. Upload a 10 GB file over a spotty connection, and TUS ensures it arrives intact.