Skip to main content

MHTML Format (MIME HTML)

Description​

MHTML (MIME HTML) is a format for archiving web pages. It combines HTML content with embedded resources (images, CSS, JavaScript) into a single file using MIME multipart encoding. MHTML files are used by Internet Explorer and other browsers for saving complete web pages.

File Extensions​

  • .mhtml - MHTML archive files
  • .mht - MHTML archive files (alias)

Implementation Details​

Reading​

The MHTML implementation:

  • Uses Python's built-in email module
  • Parses MIME multipart format
  • Extracts HTML content and embedded resources
  • Converts each part to a dictionary
  • Handles content types and locations
  • Extracts main HTML content

Writing​

Writing support:

  • Writes a multipart/related MHTML document
  • Uses content or main_content as the HTML part

Key Features​

  • Web archive format: Designed for archiving web pages
  • Multipart MIME: Uses MIME multipart encoding
  • Resource embedding: Embeds images, CSS, JavaScript
  • Nested data: Supports complex web content structures
  • Content extraction: Extracts HTML and resources

Usage​

from iterable import open_iterable

# Basic reading
with open_iterable('page.mhtml') as source:
    for part in source:
        print(part)  # Contains content type, location, and content

# Writing
with open_iterable('output.mhtml', mode='w') as dest:
    dest.write({'subject': 'Page', 'content': '<html><body>Hi</body></html>'})

Parameters​

  • encoding (str): File encoding (default: utf8)

Limitations​

  1. Web archive focus: Designed for web page archiving
  2. Complex structure: Multipart MIME structure can be complex
  3. Memory usage: Large web pages may use significant memory

Compression Support​

MHTML files can be compressed with all supported codecs:

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

Use Cases​

  • Web archiving: Archiving complete web pages
  • Web scraping: Saving web page content
  • Offline browsing: Storing web pages for offline viewing
  • Content preservation: Preserving web content

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.
  • WARC - Web archive format
  • EML - Email format (similar MIME structure)
  • MBOX - Mailbox format