Glossary
Container format
A container format is the file structure that wraps compressed image or video data together with the metadata describing it.
Updated
The distinction between the container and the compressed data inside it is the one that makes lossless removal possible. The picture is a compressed bitstream; the container is everything around it, including every metadata block.
Removing metadata is therefore an operation on the wrapper. The bitstream can be copied across untouched, because nothing being removed is part of it.
The same separation explains why "convert it to another format" does not clean a file. Conversion rebuilds the container, and conversion tools routinely carry the metadata across — a WebP converted from a JPEG commonly inherits the original camera EXIF, GPS included.
Related terms
- Chunk — A chunk is a self-describing section of a file, carrying its own type label and length.
- Lossless — Lossless means the image data comes out bit-for-bit identical to what went in.
- Re-encoding — Re-encoding is decoding an image and compressing it again, which discards detail on every pass through a lossy format.