Skip to main content

WARC Format (Web Archive)

Description​

WARC (Web ARChive) is a format for storing web archive data. It's an ISO standard format used by web archiving tools to store HTTP requests, responses, metadata, and resource records. WARC files are used by the Internet Archive and other web archiving organizations.

File Extensions​

  • .warc - WARC archive files
  • .arc - Legacy ARC format files (alias, handled as WARC)

Implementation Details​

Reading​

The WARC implementation:

  • Uses warcio library for reading
  • Parses WARC records (request, response, metadata, etc.)
  • Extracts WARC headers and content
  • Converts each WARC record to a dictionary
  • Supports compressed WARC files

Writing​

Writing support:

  • Creates WARC files
  • Writes WARC records with proper headers
  • Supports different WARC record types

Key Features​

  • Web archive format: Designed for web archiving
  • Multiple record types: Supports request, response, metadata, resource records
  • Nested data: Can contain complex web content
  • Compression support: Can work with compressed WARC files
  • Standard format: ISO standard format

Usage​

from iterable import open_iterable

# Basic reading
with open_iterable('archive.warc') as source:
    for record in source:
        print(record)  # Contains WARC record data

# Writing
with open_iterable('output.warc', mode='w') as dest:
    dest.write({
        'record_type': 'response',
        'target_uri': 'http://example.com',
        'content': b'...'  # Binary content
    })

Parameters​

No specific parameters required.

Limitations​

  1. warcio dependency: Requires warcio package
  2. Binary format: Contains binary content
  3. Complex structure: WARC records can be complex
  4. No totals: Totals counting not supported (requires full iteration)
  5. Memory usage: Large WARC files may use significant memory

Compression Support​

WARC files can be compressed with all supported codecs:

  • GZip (.warc.gz)
  • BZip2 (.warc.bz2)
  • LZMA (.warc.xz)
  • LZ4 (.warc.lz4)
  • ZIP (.warc.zip)
  • Brotli (.warc.br)
  • ZStandard (.warc.zst)

Note: WARC files often use internal compression as well.

Use Cases​

  • Web archiving: Archiving web content
  • Historical preservation: Preserving web history
  • Research: Web research and analysis
  • Compliance: Meeting web archiving requirements

Error Handling​

  • Missing dependency: optional libraries raise ImportError with an install hint (pip install 'iterabledata[<extra>]' when an extra exists).
  • Write mode: read-only formats raise WriteNotSupportedError or ValueError when opened with mode="w".
  • Bad or unsupported input: may raise ValueError, OSError, or library-specific errors.
  • See Troubleshooting for decoding, detection, and engine issues.
  • CDX - WARC index format
  • ARC - Legacy archive format (handled as WARC)