Ensure Consistency

A few of the Box APIs support headers to control consistency between your application and Box.

etag, if-match, and if-none-match

Many of the file system items (files or folders) that can be requested via the API return an etag value for the item.

For example, a file resource returns an etag in the JSON response.

curl https://api.box.com/2.0/files/12345 \
    -H "authorization: Bearer ACCESS_TOKEN"

{
  "id": 12345,
  "etag": 1,
  "type": "file",
  "sequence_id": 3,
  "name": "Contract.pdf",
  ...
}

This etag can be used as the value of a if-match or if-none-match header to either ensure a resource hasn't changed since the etag value was received, or to prevent unnecessary downloads for items that haven't changed.

For example, to fetch the same file only if it has changed, pass in the etag value in a if-none-match header.

curl https://api.box.com/2.0/files/12345 \
  -H "authorization: Bearer ACCESS_TOKEN" \
  -H "if-none-match: 1"

This API call would result in an empty response if the file had not changed.

Ensure consistent changes

The if-match header allows your application to ensure that no changes are made to items when another application or a user has made changes to the item since your application last inspected it. This helps ensure that changes aren't lost when two applications or users are changing items at the same time.

The following endpoints support this header.

The response of these APIs calls depends on the existence of the item, and whether the etag value matches the most recent version.

Prevent unnecessary request downloads

The if-none-match header allows your application to ensure that no information is downloaded for items that have not changed since your application last inspected it. This helps ensure no unnecessary information is downloaded, speeding up your application and saving on bandwidth.

The response of these APIs calls depends on the existence of the item, and whether the etag value matches the most recent version.