Glossary
RIFF chunk
A RIFF chunk is a labelled, length-prefixed block in the container format WebP is built on.
Updated
RIFF files are a sequence of four-character-code chunks, each with a length. WebP uses this to hold the compressed bitstream alongside optional EXIF, XMP and ICCP chunks.
Removing metadata from WebP takes one step more than dropping chunks. An extended-format header called VP8X carries feature flags recording which optional chunks are present, so the flags must be cleared to match. Leaving a flag set for a chunk that no longer exists produces a file strict decoders reject — the step naive implementations miss.
WebP files converted from JPEG frequently inherit the original camera EXIF, GPS included. Converting a format is not the same as cleaning it.
Related terms
- PNG text chunk — A PNG text chunk is a named section of a PNG file holding arbitrary text metadata, optionally compressed.
- ISO BMFF box — A box, sometimes called an atom, is the nested container unit that HEIC, MP4 and MOV files are built from.
- Chunk — A chunk is a self-describing section of a file, carrying its own type label and length.