Convert PNG to AVIF

Lossless means the file has to be able to reproduce every pixel exactly, so the compressor is only allowed to find patterns, never to approximate. Flat colour and sharp text are full of patterns, which is why a PNG of a simple screenshot is small. A photograph, a gradient or a soft shadow has almost none, which is why the same format turns a 1024 pixel illustration into a megabyte and a half.

AVIF is what happens when you point a modern video codec at one still frame. AV1 was designed in 2018 by the Alliance for Open Media to compete with HEVC for 4K streaming, so it spends orders of magnitude more effort predicting what an image looks like than PNG's arithmetic ever attempts. Here is what that does to real files, at this page's default quality:

• Your page is slow and the image is why: Image weight is usually the largest single thing between a visitor and a painted page, and the largest image on the screen is normally the one the Largest Contentful Paint score is measuring.
• You are paying for the bytes: Bandwidth on a CDN is billed by the gigabyte. Cutting an image by 80% cuts what it costs to serve by roughly the same amount, every month, for as long as the page is up.
• You need transparency and WebP is not small enough: WebP was the answer to this question for a decade. AVIF is meaningfully smaller again at the same visual quality, and it keeps the alpha channel just as well.
• Something keeps telling you to use a next-gen format: Lighthouse, PageSpeed Insights and most site audits flag PNGs and JPGs with a line about serving images in next-gen formats. This is the format they mean.

The exception, and it is the last row of that table: a PNG that has already been reduced to 256 colours has had most of its detail thrown away by the quantizer, and what is left is dithering noise, which is close to the worst possible input for any codec. Those files barely shrink. If the PNG came out of an export dialog with a colours dropdown, read the size on the result before you swap it in.

This is worth saying plainly because the other direction is the internet's most common conversion complaint. PNG to JPG destroys transparency, because JPEG has nowhere to put it, so every converter paints white underneath and hands you a logo in a box. AVIF has somewhere to put it: the alpha is compressed as its own plane next to the colour, and this tool never paints a background under a format that can keep one.

• Fully transparent stays fully transparent: On a 1024 pixel logo that was 92% see-through, the pixels that were completely clear came back completely clear, and the ones that were completely opaque came back completely opaque. That is 91.5% of the image, unchanged.
• Soft edges are compressed like everything else: The remaining 8.5% is the antialiased rim where the logo fades out. Those alpha values are lossy at the default 75%, and in the worst measured case one moved by about a fifth. On screen, over any background, this is invisible.
• Nothing is flattened, ever: There is no background colour setting on this page because there is nothing to set. The file that arrives transparent leaves transparent.

If you are compositing the result over something unusual, a video frame or a hard gradient, set quality to 100 and the alpha is stored losslessly along with everything else. For a logo on a web page the default is fine, and the file is a great deal smaller.

Every current browser can display an AVIF. None of them can write one. Asking a canvas for an AVIF does not fail either: it quietly hands back a PNG with the wrong extension on it, which is a failure mode worse than an error. So a converter has two options, a server or an encoder of its own, and a server is by far the cheaper one to build.

The other option is now about three and a half megabytes: libavif and aom, the reference AV1 encoder, compiled to WebAssembly and packaged out of Squoosh. This page downloads that the first time you pick AVIF and then runs it in your tab, on your own machine, on a file that never leaves the disk it is sitting on.

• Nothing is transmitted: Your file is read from your own device into your own tab. There is no server to trust with it, which is a stronger guarantee than any privacy policy, including ours.
• It works offline: Once the page and the encoder have loaded, the conversion itself needs no connection. Losing Wi-Fi halfway through changes nothing.
• There is no queue and no size-based upsell: Your device is doing the work, so the hundredth conversion costs us exactly what the first did. That is why there is no daily cap and no account.

The honest cost, twice over. The encoder is a real download, and on a slow phone connection that first wait is the one thing a server-side converter does faster. And AVIF encoding is slow by nature: AV1 does an exhaustive search that PNG never attempts, which is precisely why the file comes out so much smaller. Expect around a second for a typical image on a laptop and longer on a phone, rather than the instant a PNG to JPG conversion takes.

On most sites images are the heaviest thing on the page, and the biggest image on the screen is usually the element Largest Contentful Paint is timing. Cutting a hero image from 1.5 MB to 83 KB does not make your server faster, it removes most of what the visitor was waiting for. That is the entire mechanism, and it is why every site audit tool eventually shows you a line about next-gen formats.

• WordPress accepts AVIF uploads from 6.5 onward: Released in March 2024. On anything older the media library will reject the file type until a plugin or a filter adds it, which is worth checking before you swap the file in.
• Serve both if your audience is old: A picture element with an AVIF source and the PNG as the fallback img covers the few percent of visitors on something ancient, at the cost of storing two files. Most static site generators and image plugins now do this for you.
• Convert the asset, not the source file: Keep the PNG where you edit. Convert on the way out to the site, so the next redesign starts from the master rather than from something already compressed once.

What we will not claim: that converting your images to AVIF improves your rankings. Google ranks pages, not file formats, and image weight is one input into how fast a page feels. A faster page is worth having on its own terms, and anyone selling you AVIF as an SEO trick is selling you something else.

• Pixels are the only thing carried across: The AVIF is written fresh from the decoded image, so any EXIF block, text chunk, creation date or author field in the PNG is not in the output.
• Colour is converted to sRGB: The image is decoded through your browser's canvas, which works in sRGB, so an embedded ICC profile is applied and then not carried forward. A wide gamut PNG comes out looking correct on the web and no longer tagged.
• DPI is not a thing AVIF carries here: A PNG's pHYs chunk, which is where a 300 DPI setting lives, is dropped. It never affected the pixels, and AVIF is not a format anybody prints from anyway.
• The original PNG is untouched: Nothing here modifies or deletes your source file, so everything above still exists wherever the PNG does.

For most people this is neutral or actively useful, since stripping metadata out of an image before publishing it is something people install separate tools to do. If you need those fields preserved, a build-step tool like sharp or the reference avifenc will carry EXIF across, and this will not.