.webp Tier 1 · Deep AST Parser

WebP Image Container

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

CDN optimization proxies frequently transcode JPEGs into WebP on the fly while keeping `.jpg` URLs—causing desktop tools that trust file extensions to fail until Magic Bytes (`RIFF....WEBP`) are checked.

MIME Types image/webp

Byte Endianness little

Container Family riff

PRONOM PUID fmt/566

Canonical Spec Official Specification ↗

0xFF

Drop any .webp 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

.webp Magic Bytes & Header Offset Map

Offset: 0x00 (0 B) ASCII: RIFF....WEBP

52 49 46 46 ?? ?? ?? ?? 57 45 42 50

'RIFF' + 4-byte LE chunk size + 'WEBP' FourCC

Byte Offset	Length	Data Type	Field Name	Engineering Description
0x00 - 0x03	4 B	char[4]	riff_magic	ASCII 'RIFF'
0x04 - 0x07	4 B	uint32_le	riff_size	File size minus 8 bytes
0x08 - 0x0B	4 B	char[4]	webp_fourcc	ASCII 'WEBP'
0x0C - 0x0F	4 B	char[4]	first_chunk	'VP8 ', 'VP8L', or 'VP8X'

Upload Gateway & AppSec Advisory

.webp 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

Keep libwebp patched (>= 1.3.2, post CVE-2023-4863 Huffman heap overflow) and check both 0x00=='RIFF' and 0x08=='WEBP'.

Compiler-Verified Reference Code

Read .webp Header & Metadata Without Heavy Dependencies

✓ Zero-Dependency .webp Header Reader

import struct, sys
with open(sys.argv[1], "rb") as f:
    riff, size, webp, chunk = struct.unpack("<4sI4s4s", f.read(16))
    assert riff == b"RIFF" and webp == b"WEBP"
    print(f"WebP ({chunk.decode().strip()}), riff_size={size}B")

CI/CD & Unit Test Fixtures

Deterministic .webp Sample Files & Edge Cases

Open Full .webp Sample Matrix & Mutator →

minimalexpect: valid

minimal-vp8x.webp

Real WebP encoded by libwebp via Pillow — RIFF/WEBP container with decodable VP8L/VP8 payload.

↓ Download (58 B)

SHA-256: 297ca327517d16217664fbb2ab4e878a676db57b3050a92b5ab929259266ffde

Exact: 58 bytes

curl -fsSL https://fileformat.co/fixtures/v1/webp/minimal-vp8x.webp -o minimal-vp8x.webp \
  && echo "297ca327517d16217664fbb2ab4e878a676db57b3050a92b5ab929259266ffde  minimal-vp8x.webp" | shasum -a 256 -c

realisticexpect: valid

og-banner-1200x630.webp

Real 1200×630 lossy WebP from Pillow at quality 85 for OpenGraph-dimension checks.

↓ Download (59.2 KB)

SHA-256: 1cf094696041edb5cd955bf546811c69b1e8cdd5092cdfd765300849e2ceee2d

Exact: 60,664 bytes

curl -fsSL https://fileformat.co/fixtures/v1/webp/og-banner-1200x630.webp -o og-banner-1200x630.webp \
  && echo "1cf094696041edb5cd955bf546811c69b1e8cdd5092cdfd765300849e2ceee2d  og-banner-1200x630.webp" | shasum -a 256 -c

edge-caseRIFF Size Mismatchexpect: parser_error

truncated-riff.webp

WebP truncated inside the image payload — declared RIFF size exceeds available bytes, Pillow must raise.

↓ Download (50 B)

SHA-256: 6b6b3468c2e38c48255de9164388e169324215d8fe802e113b1b109f631deee3

Exact: 50 bytes

curl -fsSL https://fileformat.co/fixtures/v1/webp/truncated-riff.webp -o truncated-riff.webp \
  && echo "6b6b3468c2e38c48255de9164388e169324215d8fe802e113b1b109f631deee3  truncated-riff.webp" | shasum -a 256 -c

Related Specifications & Alternatives

.avif big

AVIF

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`).

.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.

.jpg mixed

JPEG

Marker-segmented DCT lossy image format (`FF D8 FF ... FF D9`), where embedded APP1 EXIF TIFF headers carry camera rotation flags (`Orientation=6`) and GPS coordinates.