LinuxWhat is the IFF file format?
The .IFF file format stands for Interchange File Format (officially EA IFF 85). The files using this extension are mainly used to exchange data across different applications and computing platforms, enabling programs on one system to share documents or media with software running on a completely different platform.
Electronic Arts initially created the universal .IFF standard in 1985, working in cooperation with Commodore-Amiga. Such files may consist of graphics, text, and even audio data - the specific content depends on the four-character sub-type declared inside the container. The two most widespread Amiga sub-formats are ILBM (Interleaved Bitmap, for color images) and 8SVX (8-bit Sampled Voice, for mono audio).
The Alias|Wavefront program (now Autodesk Maya) also makes use of the .iff extension for a closely related dialect. Here the .iff format contains the image files generated by the application - rendered frames and texture maps - stored using a FOR4 group chunk rather than the standard FORM header.
IFF's chunk-based design directly inspired RIFF (the container behind WAV and AVI) and AIFF, all of which share the same four-byte ID plus length block structure.
Security & safety
RISK: LOWIFF is a legacy container format; parsing complex nested chunk data could theoretically trigger vulnerabilities in old viewers, but no significant current exploits are known. Low risk for modern viewers on modern OSes.
Format details
in a nutshell- Amiga ILBM Bitmap (most common historical .iff) - Interleaved Bitmap format native to Amiga computers; stores 1-8 bpp planar color images with PackBits compression, HAM/EHB/AGA color modes.
- Amiga 8SVX Audio - 8-bit Sampled Voice audio sub-format storing mono 8-bit PCM or Fibonacci-delta-compressed samples at variable sample rates.
Programs that open IFF files
Windows5 apps
macOS2 apps
Technical details
deep spec| Encoding | Binary |
| Byte order | Big-endian (Motorola 68000 native; RIFF is the little-endian x86 counterpart) |
| Magic bytes | `FORM` (46 4F 52 4D) at offset 0; Maya dialect uses `FOR4` instead |
| Container structure | Hierarchical FORM/LIST/CAT group chunks → 4-char sub-type → named leaf chunks with 4-char ID + big-endian 32-bit length; each chunk padded to even byte boundary |
| Common sub-formats | ILBM (Interleaved Bitmap), 8SVX (8-bit Sampled Voice), ANIM (animation), SMUS (sheet music) |
| Compression | None at container level; ILBM uses PackBits RLE per scan line; 8SVX supports Fibonacci-delta compression |
| ILBM color depth | 1-8 bpp (EHB: 64 colors, HAM: 4,096 colors, AGA HAM8: 262,144 colors) |
| ILBM canvas limits | Up to 65,535 × 65,535 pixels per spec; practical Amiga screens ranged 320×200 to 1,280×512 |
| 8SVX audio | Mono, 8-bit PCM or delta-compressed; sample rates 8,000-28,000 Hz; parameters defined in VHDR chunk |
| Typical file size | ILBM image: 5 KB - 500 KB; 8SVX audio clip: 5 KB - 2 MB |
| Maya IFF dialect | Uses `FOR4` group chunk (not `FORM`); stores big-endian RGBA raster images for rendered frames and textures |
| Influenced formats | RIFF (WAV, AVI), AIFF, and PNG's chunk structure all derive from IFF's four-byte ID + length block design |
| Released | 1985 (EA IFF 85 specification, Electronic Arts) |
| Latest version | EA IFF 85 (no later revision published) |
| Open standard | Yes · royalty-free |
| Specification | wiki.amigaos.net |
IFF conversions
Community Q&A
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