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ImageDoctor

Reference

Image file formats, explained

Nine formats cover almost every image you will meet. This reference explains what each one is, what it is good at, where it breaks, and how to convert between them.

The nine formats side by side

FormatCompressionTransparencyAnimationBest for
JPEGLossyNoNoPhotos you send, upload or print
PNGLosslessYesAPNG onlyLogos, screenshots, graphics with transparency
WebPLossy or losslessYesYesImages on websites you control
AVIFLossy or losslessYesYesLarge photos on the web
GIFLossless, 256 coloursOn/off onlyYesShort, simple animations that must play anywhere
SVGText (vector)YesYes (CSS/SMIL)Logos, icons and diagrams on the web
HEICLossyRarely usedSequencesStoring photos on Apple devices
TIFFNone, lossless or lossyYesMulti-pageScans, print production, archival masters
BMPUsually noneRarelyNoLegacy software that requires it

Three ideas that explain most differences

Lossy or lossless

Lossless formats (PNG, lossless WebP) store every pixel exactly, so saving again never changes the image. Lossy formats (JPEG, lossy WebP, AVIF, HEIC) discard detail the eye is unlikely to notice, which makes photographs many times smaller — and makes each re-save a little worse.

Raster or vector

Every format here except SVG is raster: a fixed grid of pixels that blurs when enlarged. SVG describes shapes instead, so it stays sharp at any size — perfect for logos and icons, useless for photographs.

Made for the web, or made for everywhere

WebP and AVIF are efficient and supported by every current browser, but not by every app and upload form. JPEG and PNG are less efficient and accepted everywhere. That trade-off, not image quality, is usually what decides the format.

Every format in the reference

Convert between formats

Each converter opens with the output already chosen and runs in your browser. For any other combination, use the Image Converter.