Image MIME Reference
AVIF
AV1 Image File Format
image/avif
VS
PiCture eXchange
image/x-pcx
PCX
A complete technical comparison of AV1 Image File Format and PiCture eXchange — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
AVIF wins on browser support
Feature Support
| Feature | AVIF | PCX |
|---|---|---|
| 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 |
AV1 Image File Format
image/avif
Extension
.avif
Container
HEIF / ISOBMFF
Compression
AV1 Lossy / AV1 Lossless
Algorithm
AV1
Color Depth
8-bit, 10-bit, 12-bit
Developed by
Alliance for Open Media (AOMedia)
Released
2019
Magic Bytes
XX XX XX XX 66 74 79 70 61 76 69 66
PiCture eXchange
image/x-pcx
Extension
.pcx
Container
ZSoft Proprietary Header (128 bytes)
Compression
Run-Length Encoding (RLE)
Algorithm
ZSoft RLE
Color Depth
1-bit (Monochrome), 4-bit (16 colors), 8-bit (256 colors), 24-bit (True Color)
Developed by
ZSoft Corporation
Released
1985
Magic Bytes
0A (followed by version, e.g., 0A 05 01 08)
Browser Support Comparison
| Browser | AVIF | PCX |
|---|---|---|
Chrome
|
✓ 85+
|
✕ |
Firefox
|
✓ 93+
|
✕ |
Safari
|
✓ 16+
|
✕ |
Edge
|
✓ 121+
|
✕ |
IE (Legacy)
|
✕ | ✕ |
AVIF
AVIF Strengths
- Best-in-class compression — typically 20–50% smaller than WebP at equivalent quality
- Native HDR and wide color gamut (BT.2020) support
- Supports 8, 10, and 12-bit color depth
Limitations
- Encoding is highly CPU-intensive — significantly slower than JPEG or WebP
- Requires Edge 121+ (not supported in earlier Edge versions)
- Limited support in native desktop image viewers
PCX
PCX Strengths
- Incredibly simple RLE algorithm makes it very fast to decode, which was historically vital for early 3D video game engines
- Retains crisp, lossless pixel data suitable for pixel art and interface assets
- Well-documented and highly supported by older desktop publishing and image editing software
Limitations
- Extremely inefficient compression by modern standards, producing large file sizes compared to PNG
- Lacks modern imaging features such as alpha channel transparency, EXIF metadata, and color profiles
- Zero support in web browsers; must be converted to PNG for web use
When to choose which format
AVIF
Use AVIF when…
- Next-Gen Websites
- HDR Photography
- High-Quality Web Images
PCX
Use PCX when…
- MS-DOS and Early Windows Graphics
- 1990s Video Game Assets (Textures, UI)
- Retro Computing Archival