What is the difference between HTTP 200 and 206 responses?

HTTP 200 means the server is returning the complete resource. HTTP 206 Partial Content means the server is returning only the requested byte range, indicated by the Content-Range header. A 206 response is triggered when the client sends a Range header and the server supports range requests (indicated by Accept-Ranges: bytes). If the server does not support ranges, it ignores the Range header and returns 200 with the full resource.

How do I implement resumable file uploads without a third-party library?

Create three endpoints: POST /upload/init to create an upload session (returns an uploadId and starting offset), PATCH /upload/:id to receive chunks (validate Upload-Offset matches server state, append to file), and HEAD /upload/:id to report current offset. The client slices the file into chunks using File.slice(), sends each chunk with the correct offset, and on failure queries HEAD to discover where to resume. Store upload metadata (filename, total size, bytes received) alongside the partial file.

When should I use the tus protocol vs a custom chunked upload?

Use tus when you want a battle-tested, interoperable protocol with client libraries for every major platform (JavaScript, iOS, Android, Go, Python). tus handles edge cases like concurrent chunk uploads, checksum verification, and upload expiration. Build a custom solution only when tus does not fit your constraints, for example if you need tight integration with a specific cloud storage API or your upload semantics differ significantly from the tus PATCH-based model.

Why does my Range request return 200 instead of 206?

The server likely does not support range requests for that resource. Check for the Accept-Ranges: bytes header in a normal GET response. If it is absent or set to 'none', the server will not honor Range headers. Dynamic responses from application code typically do not support ranges unless explicitly implemented. Static file servers (Nginx, Apache, S3) support ranges by default. Also verify the Range header format is correct: 'Range: bytes=0-999' not 'Range: 0-999'.

How do I handle upload size limits properly?

Enforce limits at multiple layers: Nginx or Apache (client_max_body_size), application middleware (Express body-parser limit option or Spring max-file-size), and in your upload initialization endpoint (reject Upload-Length values exceeding your limit before any data is sent). Return HTTP 413 Payload Too Large with a clear error message stating the maximum allowed size. For chunked uploads, validate the declared total size during initialization and also track actual bytes received to prevent clients from exceeding the limit by sending more data than declared.

Large File Uploads and Partial Content