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What is a Chunked Upload?

A chunked upload divides a file into byte ranges that are transmitted and tracked independently. A resumable implementation can retry missing chunks without sending the entire file again.

How Chunked Uploads work

A resumable uploader establishes transfer state, divides the source into addressed parts, and records which byte ranges the server has accepted. Parts may travel sequentially or concurrently, after which a completion operation verifies and assembles the object. This protocol layer sits before media inspection and processing, allowing large ingest jobs to survive connection loss while requiring explicit handling of offsets, duplicate retries, expiry, and final integrity.

Key facts

  1. A resumable protocol needs a stable upload identifier and an authoritative offset or part list; trusting only the client’s local progress can skip bytes after a lost response.
  2. Retries should be idempotent or checksum-verified because a server may have stored a chunk even when the acknowledgement never reached the client.
  3. Valid individual parts do not prove a valid file. Finalization must verify ordering, expected total length, and preferably a whole-object digest before downstream processing begins.

When Chunked Uploads matter

Use chunked uploads for large files or clients on unstable networks, where restarting a transfer would be costly. The server must validate chunk order, size, and final assembly or it may produce incomplete files.

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