Decision guide
Best image format for websites
Web images are judged on transfer size, native browser decoding and how little work the browser has to do before first paint. The engine weights those dimensions and ranks every image format in the knowledge graph accordingly.
Short answer: AVIF ranks first (92/100) because browsers render it natively, so no conversion step is needed at request time.
The ranking, and the reasoning behind it
Scores are computed from structured facts in the knowledge graph, weighted for this specific question. Nothing here is written by hand, and every line of reasoning traces back to a recorded fact.
#1AVIF
92/100
AVIF is an AV1-based image format with the strongest compression of the web formats.
All AVIF factsWhy it scores well
- Web suitability 100/100 — browsers render it natively, so no conversion step is needed at request time; lossy compression keeps transfer sizes and Core Web Vitals in check.
- Browser compatibility 100/100 — every major browser engine renders it natively; at least one shipping browser renders it.
- Compression efficiency 100/100 — it compresses lossily, which produces much smaller files than lossless coding; it uses a recent codec generation, which encodes more efficiently than older designs.
#2WebP
92/100
WebP is Google's web image format offering lossy and lossless modes with alpha.
All WebP factsWhy it scores well
- Web suitability 100/100 — browsers render it natively, so no conversion step is needed at request time; lossy compression keeps transfer sizes and Core Web Vitals in check.
- Browser compatibility 100/100 — every major browser engine renders it natively; at least one shipping browser renders it.
- Decode performance 100/100 — smaller payloads mean less I/O and faster first paint; mature formats benefit from hardware and SIMD-optimised decoders.
#3JPEG
91/100
JPEG is the lossy photographic image format that cameras, phones and websites default to.
All JPEG factsWhy it scores well
- Web suitability 100/100 — browsers render it natively, so no conversion step is needed at request time; lossy compression keeps transfer sizes and Core Web Vitals in check.
- Browser compatibility 100/100 — every major browser engine renders it natively; at least one shipping browser renders it.
- Decode performance 100/100 — smaller payloads mean less I/O and faster first paint; mature formats benefit from hardware and SIMD-optimised decoders.
#4HEIC
68/100
HEIC is Apple's default photo format, storing HEVC-compressed images at half JPEG's size.
Why it scores well
- Compression efficiency 100/100 — it compresses lossily, which produces much smaller files than lossless coding; it uses a recent codec generation, which encodes more efficiently than older designs.
- Decode performance 100/100 — smaller payloads mean less I/O and faster first paint; mature formats benefit from hardware and SIMD-optimised decoders.
- Future-proofing 100/100 — it is actively maintained and current; open specifications outlive the companies that create them.
All HEIC factsWhere it loses points
- Browser compatibility 33/100 — native browser support is incomplete or undocumented.
#5PNG
66/100
PNG is a lossless raster format with full alpha transparency, built for graphics.
Why it scores well
- Browser compatibility 100/100 — every major browser engine renders it natively; at least one shipping browser renders it.
- Future-proofing 88/100 — it is actively maintained and current; open specifications outlive the companies that create them.
- Web suitability 67/100 — browsers render it natively, so no conversion step is needed at request time; the specification is open, so tooling and CDNs implement it freely.
All PNG factsWhere it loses points
- Compression efficiency 23/100 — it stores data losslessly, so files stay large; its codec generation predates modern entropy coding and block partitioning.
- Decode performance 43/100 — large lossless payloads cost bandwidth and memory.
#6BMP
62/100
BMP is an uncompressed Windows raster format that trades size for simplicity.
Why it scores well
- Browser compatibility 100/100 — every major browser engine renders it natively; at least one shipping browser renders it.
- Web suitability 67/100 — browsers render it natively, so no conversion step is needed at request time; the specification is open, so tooling and CDNs implement it freely.
All BMP factsWhere it loses points
- Compression efficiency 23/100 — it stores data losslessly, so files stay large; its codec generation predates modern entropy coding and block partitioning.
- Decode performance 43/100 — large lossless payloads cost bandwidth and memory.
#7SVG
61/100
SVG is an XML vector format that stays sharp at any size.
Why it scores well
- Browser compatibility 100/100 — every major browser engine renders it natively; at least one shipping browser renders it.
- Future-proofing 88/100 — it is actively maintained and current; open specifications outlive the companies that create them.
- Web suitability 67/100 — browsers render it natively, so no conversion step is needed at request time; the specification is open, so tooling and CDNs implement it freely.
All SVG factsWhere it loses points
- Compression efficiency 0/100 — it stores data losslessly, so files stay large; its codec generation predates modern entropy coding and block partitioning.
- Decode performance 43/100 — large lossless payloads cost bandwidth and memory.
#8GIF
60/100
GIF is a 256-colour raster format best known for short looping animations.
Why it scores well
- Browser compatibility 100/100 — every major browser engine renders it natively; at least one shipping browser renders it.
- Web suitability 67/100 — browsers render it natively, so no conversion step is needed at request time; the specification is open, so tooling and CDNs implement it freely.
All GIF factsWhere it loses points
- Compression efficiency 23/100 — it stores data losslessly, so files stay large; its codec generation predates modern entropy coding and block partitioning.
- Future-proofing 25/100 — it is marked legacy or deprecated in the knowledge graph; a successor format already exists and is taking over its use cases.
- Decode performance 43/100 — large lossless payloads cost bandwidth and memory.
How this ranking is calculated
Each format is scored 0–100 on every dimension the graph can evaluate for it. For this question the dimensions carry these weights:
- web ×3
- browser compatibility ×3
- compression efficiency ×2
- performance ×2
- future proofing ×1
No machine learning is involved. The engine is deterministic: the same facts always produce the same ranking, and adding a new fact to the graph updates it automatically.
Frequently asked questions
Should I still serve JPEG on the web?
- JPEG remains the safest universal fallback because every browser decodes it, but modern formats reach the same perceived quality at a smaller size. Serve a modern format first and keep JPEG as the fallback in a picture element.
Does image format affect Core Web Vitals?
- Yes. Largest Contentful Paint is usually an image, so a smaller encoded payload directly improves the metric on slow connections.