.avif Tier 1 · Deep AST Parser

AVIF (AV1 Image File Format)

Royalty-free HDR & wide-gamut next-gen web image format wrapping AV1 keyframes inside an ISO Base Media (`ftyp`) container (`major_brand` = `avif` or `avis`).

Shares the ISOBMFF box container with HEIC and MP4; requires reading offset `0x08` (`avif` for still images, `avis` for animated image sequences).

MIME Types image/avif

Byte Endianness big

Container Family isobmff

Canonical Spec Official Specification ↗

0xFF

Drop any .avif file (even 100 GB+) to inspect locally

Reads tiny File.slice() header/footer pages in a sandboxed Web Worker · 0 Bytes Uploaded

Binary Signature & Wire Layout

.avif Magic Bytes & Header Offset Map

Offset: 0x04 (4 B) ASCII: ftypavi

66 74 79 70 61 76 69

ISOBMFF ftyp box with 'avif' or 'avis' brand prefix

Byte Offset	Length	Data Type	Field Name	Engineering Description
0x00 - 0x03	4 B	uint32_be	ftyp_size	Box byte length
0x04 - 0x07	4 B	char[4]	box_type	'ftyp' FourCC
0x08 - 0x0B	4 B	char[4]	major_brand	'avif' (still) or 'avis' (sequence)

Upload Gateway & AppSec Advisory

.avif Security & Polyglot Risk Matrix

Risk Level: low

Arbitrary Code / Macros

NO (Inert Data)

Pickle Deserialization

SAFE (No Pickle VM)

XML External Entity (XXE)

NONE

Polyglot Prepend Risk

LOW (Strict 0x00 Magic)

Backend Upload Validation Recommendation

Inspect `ispe` box dimensions before full pixel decoding to block decompression bombs (e.g. 65000x65000px 10KB solid-color AV1 frames).

Compiler-Verified Reference Code

Read .avif Header & Metadata Without Heavy Dependencies

✓ Zero-Dependency .avif Header Reader

import struct, sys
with open(sys.argv[1], "rb") as f:
    sz, box, brand = struct.unpack(">I4s4s", f.read(12))
    assert box == b"ftyp" and brand in (b"avif", b"avis")
    print(f"AVIF brand={brand.decode()}")

CI/CD & Unit Test Fixtures

Deterministic .avif Sample Files & Edge Cases

Open Full .avif Sample Matrix & Mutator →

minimalexpect: valid

minimal-128x128.avif

Real AVIF encoded by libavif via pillow-avif: ftyp avif, decodable AV1 primary item.

↓ Download (2.4 KB)

SHA-256: c1d62b9cfb1ac1ef878cabf2033ef0bd25067ff3fcc032aa0dc5c2c833687918

Exact: 2,446 bytes

curl -fsSL https://fileformat.co/fixtures/v1/avif/minimal-128x128.avif -o minimal-128x128.avif \
  && echo "c1d62b9cfb1ac1ef878cabf2033ef0bd25067ff3fcc032aa0dc5c2c833687918  minimal-128x128.avif" | shasum -a 256 -c

realisticexpect: valid

photo-640x480.avif

Real AV1 Image File Format still encoded by libavif at 640×480.

↓ Download (39.7 KB)

SHA-256: 66e43e004db1ebc43bcf2b7e3f44198d43d83ec0d828b064a69e5ffa1254667e

Exact: 40,636 bytes

curl -fsSL https://fileformat.co/fixtures/v1/avif/photo-640x480.avif -o photo-640x480.avif \
  && echo "66e43e004db1ebc43bcf2b7e3f44198d43d83ec0d828b064a69e5ffa1254667e  photo-640x480.avif" | shasum -a 256 -c

edge-caseTruncated ISOBMFF Boxexpect: parser_error

truncated-box.avif

Real AVIF truncated inside the mdat payload — libavif decoder must raise.

↓ Download (2.4 KB)

SHA-256: 8fc0516c40d536a757998b236c6d6d96a4b5a36874d8b17c72a64829251e0ae4

Exact: 2,414 bytes

curl -fsSL https://fileformat.co/fixtures/v1/avif/truncated-box.avif -o truncated-box.avif \
  && echo "8fc0516c40d536a757998b236c6d6d96a4b5a36874d8b17c72a64829251e0ae4  truncated-box.avif" | shasum -a 256 -c

Related Specifications & Alternatives

.heic big

HEIC

Apple iOS default camera photo container encapsulating HEVC (H.265) intra-coded image tiles, depth maps, and EXIF metadata inside an ISO Base Media (`ftyp`) box hierarchy.

.webp little

WebP

RIFF-based modern raster image container supporting lossy (`VP8 `), lossless (`VP8L`), and extended alpha/animated/EXIF (`VP8X`) bitstreams.

.png big

PNG

Lossless CRC-checked chunked raster image format, heavily used in AI workflows (ComfyUI / Stable Diffusion) to store generation graphs and prompts inside `tEXt`/`iTXt` chunks.