AVIF (AV1 Image File Format) packages still images using AV1 video compression. Released in 2019 and reaching widespread browser support in 2023–2024, AVIF is the smallest mainstream image format: typical photographic content is 20% smaller than WebP and 50% smaller than JPG at equivalent visual quality.
The trade-off is decode cost. AVIF takes 2–3× as long to decode as JPG on the same hardware. For typical web use this is invisible (browsers decode in parallel and most pages are bottlenecked on download), but it can show up on image-heavy pages on older mobile devices.
AVIF is the right choice when bandwidth or storage cost is a real constraint and your audience is on modern browsers. It's not yet a safe replacement for WebP in every context — the WebP advantage of universal modern-browser support and ubiquitous tooling is still meaningful. Many sites serve AVIF with a WebP fallback via the <picture> element.
History — introduced 2019
By: Alliance for Open Media (AOMedia)
The Alliance for Open Media (Google, Mozilla, Netflix, Microsoft, Amazon, etc.) standardised AV1 in 2018 as a royalty-free video codec. AVIF — using the same compression for still images — followed in 2019. Browser support arrived gradually: Chrome in 2020, Firefox in 2021, Safari in 2022. By 2024 AVIF was supported in every major browser at current versions.
How it works
AVIF wraps a single intra-coded AV1 frame in an ISOBMFF container (the same container used by MP4 video). The AV1 intra-frame prediction is more sophisticated than VP8's (used by WebP) — it has more block sizes, more prediction modes, and better entropy coding — which is why AVIF compresses better.
AVIF supports the same alpha transparency, animation, lossy and lossless modes as WebP, plus HDR (high dynamic range) imagery and wider colour gamuts. For most web use cases, the lossy mode is what's relevant.
Strengths and weaknesses
Strengths
- Best-in-class compression — typically 20% smaller than WebP and 50% smaller than JPG at equivalent visual quality.
- Supports HDR and wide colour gamuts (Rec.2020, P3) — the only mainstream image format that does.
- Royalty-free — no patent encumbrance on either the AV1 codec or the AVIF container.
- Full alpha transparency and animation in the same format as still imagery.
Weaknesses
- Decode is 2–3× slower than JPG. Encoding is also slow — sometimes 10–30× slower than JPG/WebP at equivalent settings.
- Tooling is still maturing. Many CMSes and image processors don't yet handle AVIF natively.
- Browser support arrived recently — some older mobile devices on the long tail of Android may not have AVIF decoders.
- AVIF EXIF support is technically defined but inconsistently implemented across tools.
When to use it
- High-traffic websites where bandwidth cost is material
- Image-heavy media sites (publishers, e-commerce)
- Sites delivered globally where mobile data costs are a factor for the audience
- Apps and PWAs where storage size matters
- HDR photography for the small (but growing) audience with HDR displays
When NOT to use it
- Email — virtually no email client renders AVIF. Use WebP or JPG.
- Workflows that need to interop with older tools — AVIF support is still maturing in many image editors.
- Sites with significant legacy-browser traffic — provide a WebP or JPG fallback via <picture>.
- Real-time encoding workflows — AVIF encode speed is much slower than JPG / WebP.
Browser support
Global coverage: 93%
| Browser | Support |
|---|---|
| Chrome | 85+ (2020) |
| Firefox | 93+ (2021) |
| Safari | 16+ (2022) |
| Edge | 85+ (2020) |
| Legacy / notes | Not supported in Internet Explorer or any browser older than ~2022. |
Performance considerations
- AVIF saves significant bandwidth — typical 20% reduction vs WebP, 50% vs JPG. On image-heavy pages this is a meaningful LCP improvement.
- Decode is 2–3× slower than JPG. Mostly invisible because browsers decode in parallel and download is the bottleneck — but worth knowing on extremely image-dense pages.
- Encode is dramatically slower than JPG / WebP. For dynamically-generated thumbnails, this matters; for static site builds, you do it once and it's fine.
SEO considerations
- Better compression → faster LCP → better Core Web Vitals scores → small but real ranking lift on image-heavy sites.
- Google indexes AVIF correctly in image search.
- The standard accessibility rules apply — alt text, descriptive filenames, etc.
Common mistakes
- Serving AVIF without a WebP or JPG fallback. Use <picture> with multiple sources so older clients still render an image.
- Encoding AVIF at full quality (effort 10) for every image — encode is much slower at high effort settings. Effort 6 produces files within 5% of effort 10 in a fraction of the time.
- Assuming AVIF will load faster on every device — on older mobile, the decode penalty can outweigh the smaller download.
- Using AVIF as a source format. Convert from a lossless source (PNG, TIFF) — re-encoding a JPG as AVIF inherits the JPG artefacts.
Frequently asked questions
- Is AVIF better than WebP?
- For pure file size, yes — typically 20% smaller at equivalent quality. For overall practicality today, WebP still wins on tooling support, encoding speed and decode cost. AVIF is the right pick for sites where every byte matters and you can serve a WebP fallback.
- What browsers support AVIF?
- Chrome 85+ (2020), Firefox 93+ (2021), Safari 16+ (2022), Edge 85+ (2020). About 93% of current global browser usage. Older browsers need a WebP or JPG fallback.
- Why is AVIF encoding so slow?
- AVIF uses AV1 video compression for still images. AV1 prioritises compression ratio over encoding speed — at high effort settings, encoding is 10–30× slower than JPG. For static site builds it's a one-time cost; for dynamic image processing, lower effort settings (e.g. effort 4) provide a more reasonable speed.
- Can I use AVIF for emails?
- No — virtually no email client renders AVIF. For email marketing and transactional email, stick with JPG (universal) or PNG (universal with transparency).
- Does AVIF support transparency?
- Yes — full alpha transparency in both lossy and lossless modes, same as WebP.