Item Metadata API#


Internet Archive organizes its holdings into items, directories of files containing content and metadata. These items are located across a distributed cluster of data nodes.

The Metadata API (MDAPI) permits callers to fetch an item’s various metadata in a single transaction. With the appropriate permissions, a user may also add or update the item’s metadata, and may even store ad hoc JSON data in a transaction-safe manner. MDAPI may be thought of as a digital card catalog for Internet Archive’s holdings.

The API is broken into two conceptual operations: Read and Write. The documentation here mostly focuses on using these operations via its HTTP RESTful endpoint. Details about the internal MDAPI PHP library are explained as well.

Item identifiers#

MDAPI requires a single item identifier for all operations. This identifier is a unique string naming the item. (More information on item identifiers may be found here.)

MDAPI cannot operate on more than one item at a time. There is no wildcarding of item identifiers.


Although most information returned by Metadata Read is publicly available, certain user JSON fields require authorization.

All Metadata Write operations require authorization.

In both cases, the caller may supply either the user’s S3 access/secret keys or their Internet Archive HTTP cookies (obtained at interactive login).

Internet Archive’s S3 keys can be sent using the Authorization: LOW header. See “S3 Authentication” for more information.

Internet Archive cookies (in particular, logged-in-user and logged-in-sig) should be sent using the standard HTTP Cookie: header.

In general, cookies should only be used by browsers and S3 keys for programmatic access.


Metadata Read supports response compression to reduce bandwidth.

Clients which support compression should include an Accept-Encoding: deflate, gzip header in requests. The client should be prepared to accept compressed or uncompressed content.

See RFC 7230 Section 4.2 for more information.

Metadata Read#

The Item Metadata Read API is described here.

Metadata Write#

The Item Metadata Write API is described here.

Applications writing metadata should be mindful of concurrency problems when writing metadata. That topic is covered here.