WARC

File Format
Name	WARC
Ontology	Electronic File Formats Archiving WARC
Extension(s)	.warc, .warc.gz
MIME Type(s)	application/warc, application/warc-fields
PRONOM	fmt/289

WARC is an archive file format which has been the predominant format for Web (HTTP) archives from 2009 to (as of 2019) the present; it is also used for archives of documents collected through other prococols (e.g. FTP), and could technically be used to store a collection of ordinary files. It is the successor to the ARC format. It was developed under the auspices of the International Internet Preservation Consortium, and standardized as ISO 28500:2009, Information and documentation -- WARC file format. WARC was developed as an extension to ARC in part to provide better capabilities for managing Web archives for the long term, allowing for capture of more metadata about the circumstances of archiving.

WARC files are often compressed using gzip, resulting in a .warc.gz extension. In cases where the warc.gz file needs to randomly accessed (namely, as part of web archives accessible page-by-page), this will consist of one gzip stream for each WARC record, concatenated together (which makes for a valid gzip file). This allows any single record to be accessed by an offset, and (when the entire file is decompressed) also preserves the original WARC.

There is also a specification for a Web Archive Metadata File. Another metadata format used with WARC files is CDX.

Specifications

• Draft of ISO-DIS 28500 As circulated for ISO ballot and approval.
• WARC, Web ARChive file format, from Library of Congress resource on Sustainability of Digital Formats
• Working drafts for WARC specification
• The WARC Format v. 1.0
• WARC Specifications

Sample files

• Test WARC Files warc.gz file from Internet Archive.

Tools

• WARC Tools (in Python)
  • Some history on the Python tools is available on here on the COPTR wiki.
• warcat: Tool and library for handling Web ARChive (WARC) files.
• Warcreate (for Google Chrome)
• warcbase platform
• WARC Input and Output Formats for Hadoop
• webarchiveplayer

Other links and references

• The WARC File Format (ISO 28500) - Information, Maintenance, Drafts
• Slide show on WARC
• The WARC Ecosystem (Archive Team)
• Web Archive Analysis Workshop
• Warcbase Wiki
• Discussion of WARC format 1.1, under development
• Merging & Deduping WARC files
• Harvesting the Twitter Streaming API to WARC files
• The great WARC adventure: Using SIPS, AIPS, and DIPS to document SLAAPs
• WARC Work
• WARC MIME Media Type (as of now unregistered, but a suggested value exists)