File format glossary

Plain-English definitions of image formats, codecs, compression and the other terms you run into when you convert files.

A

AVIFA newer image format based on the AV1 video codec. Very small files, but not every app opens it.

B

BitrateBitrate is how much data a media file uses per second. Higher bitrate means better quality and a bigger file.

C

CodecA codec is the method that compresses and decompresses audio, video or images inside a file format.Container (media container)A media container is the file format that holds audio, video and subtitle streams together with timing and metadata. MP4, MKV and MOV are containers.

D

DitheringDithering mixes dots of the few colors an image is allowed to use so that, from a distance, they blend into shades the palette doesn't have.

H

HEICHEIC is the iPhone's default photo format since iOS 11. It is about half the size of a JPG at the same quality.HEIFHEIF is the general image container standard. HEIC is the version Apple uses.HEVCHEVC, or H.265, is a video codec that makes files about half the size of H.264. HEIC photos use it too.

L

LosslessLossless compression makes a file smaller and keeps every pixel or sample exactly. PNG is lossless.LossyLossy compression makes files much smaller by removing detail you are unlikely to notice. JPG is lossy.

M

Metadata (EXIF)EXIF metadata is hidden data saved inside a photo, such as the date, GPS location and camera settings.MinificationMinification removes characters code doesn't need to run, such as whitespace, comments and long local names, to make files smaller.

R

RasterizeTo rasterize means to turn a vector image, like an SVG, into a fixed grid of pixels, like a PNG.RAW imageA RAW image is the unprocessed sensor data a camera saves, plus metadata and a small preview. It needs developing before it becomes a normal picture.

S

STL (3D model file)STL is the standard file format for 3D printing. It stores the surface of a model as a mesh of triangles, with no color, texture or units.

T

TranscodingTranscoding is converting media from one encoding to another, like HEIC to JPG or MOV to MP4.

W

WebPWebP is Google's image format for the web. It is smaller than JPG and PNG and works in all modern browsers.WebVTTWebVTT is the W3C text format for captions and subtitles on the web. Files end in .vtt and work with the HTML5 track element.

Z

ZIP (archive)ZIP is an archive format that packs many files and folders into one compressed file. Every major operating system can open it.