What AVIF actually is
AVIF is a still image stored as a single AV1 video keyframe inside a HEIF container. AV1 is the royalty-free video codec developed by the Alliance for Open Media, and it brings video-grade prediction and filtering to photographs and graphics. The practical result is that AVIF files are routinely half the size of JPG and 20 to 40 percent smaller than WebP at a similar visual quality. Every current version of Chrome, Firefox, Edge and Safari can display it, though Safari only joined in version 16.4, released in March 2023.
On this page the AVIF encoder is libaom compiled to WebAssembly. It runs in a Web Worker so the page stays responsive, and when your browser allows multi-threaded WebAssembly the encoder uses several cores. Nothing is uploaded; the only limit on speed is your own CPU.
What survives the conversion and what does not
A PNG carries lossless pixels, an optional alpha channel, sometimes 16 bits per channel, and occasionally an ICC profile or text metadata. Here is what happens to each:
- Transparency is kept. AVIF supports an alpha plane, and the encoder preserves it, including soft, partially transparent edges. This makes the format usable for logos and cut-out graphics, not just photos.
- The pixels become lossy. Detail is removed according to the quality slider. The visible effect differs from JPG: rather than blocky ringing, AVIF tends to smooth fine texture and can slightly soften very thin lines or small text.
- Depth is reduced to 8 bits and colour is normalised to sRGB. The image is decoded through a canvas, which applies any embedded profile and discards it. Text chunks and EXIF are removed as well.
- Dimensions are unchanged. If you need a smaller image, run it through Resize image first.
Setting the quality slider
The slider spans 20 to 95 and defaults to 80. Do not assume that 80 in AVIF means the same thing as 80 in JPG; the scales are not calibrated against each other. In practice an AVIF at 70 often looks at least as good as a JPG at 85. For graphics with crisp edges, stay at 80 or above and inspect the result at full size, because softening on lettering is the artefact people notice first. For illustrations with gradients, 65 to 75 usually looks identical to the source while shrinking the file dramatically.
Typical results, which depend heavily on the content:
- A 1600x1000 flat illustration, 900 KB as PNG, usually lands between 60 and 120 KB.
- A 1024x1024 logo with a transparent background, 280 KB as PNG, often comes out under 40 KB.
- A 3000x2000 photo saved as a 9 MB PNG typically ends up around 300 to 500 KB, versus roughly 500 to 800 KB as WebP.
Expect the encode to take a few seconds per megapixel on a laptop and noticeably longer on a phone. That is normal for AV1; the codec spends its effort searching for the best prediction, which is where the small files come from.
When WebP is the safer choice
AVIF still fails to open in a lot of places outside the browser: Windows 10 without the paid extension, older Photoshop and most email clients, many content management systems that generate thumbnails, and any device stuck on an older Safari. If the file is going anywhere other than your own website with a proper fallback, produce a WebP with PNG to WebP instead, or keep both. Very small images are also a poor fit: the AVIF container has a few hundred bytes of overhead, so a 64-pixel icon can end up bigger than its PNG. The guide WebP vs AVIF vs JPEG goes deeper into where each format wins.
Honest limits
This is a single-frame, 8-bit, sRGB converter. It cannot create HDR or 10-bit AVIF, cannot produce a lossless AVIF, and gives you no control over chroma subsampling beyond the quality value. Large PNGs are constrained by browser canvas memory, so a 40-megapixel source may fail on a tablet where it would succeed on a desktop. For a pixel-perfect archive, the PNG you started with remains the master copy.