ISO 28500:2009 specifies the WARC file format:

• to store both the payload content and control information from mainstream Internet application layer protocols, such as the Hypertext Transfer Protocol (HTTP), Domain Name System (DNS), and File Transfer Protocol (FTP);
• to store arbitrary metadata linked to other stored data (e.g. subject classifier, discovered language, encoding);
• to support data compression and maintain data record integrity;
• to store all control information from the harvesting protocol (e.g. request headers), not just response information;
• to store the results of data transformations linked to other stored data;
• to store a duplicate detection event linked to other stored data (to reduce storage in the presence of identical or substantially similar resources);
• to be extended without disruption to existing functionality;
• to support handling of overly long records by truncation or segmentation, where desired.