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Image MIME Reference
Compressed-XCF

Compressed GIMP XCF Image

image/x-compressed-xcf
VS

Image Exchange Format

image/ief
IEF

A complete technical comparison of Compressed GIMP XCF Image and Image Exchange Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Compressed-XCF IEF
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
Compressed GIMP XCF Image
image/x-compressed-xcf
Extension
.xcf.gz.xcf.bz2.xcfgz.xcfbz2
Container Gzip or Bzip2 Archive
Compression Gzip (Deflate) / Bzip2
Algorithm
DeflateBWT (Burrows-Wheeler)
Color Depth 8-bit (Per Channel), 16-bit (Integer/Floating Point), 32-bit (Integer/Floating Point)
Developed by The GIMP Team
Released 1995
Magic Bytes
1F 8B 08 (gzip) or 42 5A 68 (bzip2)
Full Compressed-XCF reference →
Image Exchange Format
image/ief
Extension
.ief
Container TIFF Class B (TIFF-B)
Compression Lossless (MH, MR, MMR) / Uncompressed
Algorithm
MHMRMMRUncompressed
Color Depth 1-bit (Monochrome)
Developed by IETF Network Fax Working Group
Released 1992
Magic Bytes
49 49 2A 00 (Little-endian) / 4D 4D 00 2A (Big-endian)
Full IEF reference →

Browser Support Comparison

Browser Compressed-XCF IEF
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
Compressed-XCF

Compressed-XCF Strengths

  • Drastically reduces the massive file sizes of standard XCF project files, saving significant disk space
  • Preserves 100% of the non-destructive editing data (layers, masks, paths, guides) from the GIMP workspace
  • Uses standard, universally supported compression algorithms (gzip/bzip2) meaning the archive can be rescued or extracted by standard OS tools if GIMP is unavailable
Limitations
  • Increases file load and save times due to the CPU overhead required to compress and decompress the massive pixel arrays
  • Impossible for automated tools to parse metadata or dimensions without first unarchiving the payload into memory
  • File extension combinations (.xcf.gz) can confuse basic MIME sniffers which stop reading at the .gz extension
IEF

IEF Strengths

  • Provided a standard method for exchanging bi-level fax images during the early days of the Internet
  • Supported multi-page documents
  • Leveraged the highly resilient and well-documented TIFF container
Limitations
  • Completely obsolete and unsupported in modern computing environments
  • Strictly limited to 1-bit monochrome data, lacking color or grayscale capabilities
  • Magic bytes overlap completely with standard TIFF, making specific filetype detection difficult without parsing internal tags

When to choose which format

Compressed-XCF
Use Compressed-XCF when…
  • GIMP Multi-layer Project Archival
  • Saving disk space for complex raster edits
  • Open-source graphic design workflows
IEF
Use IEF when…
  • Legacy Fax Transmissions
  • Early Internet Gateways
  • Archival

More comparisons

Compressed-XCF vs ACES → IEF vs ACES → Compressed-XCF vs APNG → IEF vs APNG → Compressed-XCF vs AVCI → IEF vs AVCI → Compressed-XCF vs AVCS → IEF vs AVCS → Compressed-XCF vs AVIF → IEF vs AVIF → All comparisons →
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