The Box API supports two distinct methods of file upload. The direct file upload API supports files up to 50MB in size and sends all the binary data to the Box API in 1 API request.

The chunked upload APIs support files from 20MB in size and allow an application to upload the file in parts, allowing for more control to catch any errors and retry parts individually.

Upload limits

Upload limits are dictated by the type of account of the authenticated user. More information can be found in our community article on this topic.

Preflight check

The Pre-flight check API allows an application to verify that a file will be accepted by Box before it uploads any bytes. It can both be used for new files, as well as uploading new versions of existing files.

Learn more about pre-flight checks

Upload domain

Uploads to Box happen via a different domain (upload.box.com) than regular API calls. This is something to keep in mind when writing your own upload code. All the Box SDKs will take care of choosing the right domain for the right API call.