Turn an AVIF file into a JPG in your browser

AVIF is an image format built on the AV1 video codec. It was published in February 2019 by the Alliance for Open Media, the same group that had created the codec itself. An AVIF file holds a single AV1 frame inside a HEIF container, the same box for data that an iPhone uses for HEIC photos[1]. That is where its strength comes from: at comparable image quality an AVIF file is roughly half the size of the same picture stored as JPG[2]. AVIF also stores transparency, animation, 10- and 12-bit colour and HDR, meaning an extended range of brightness[1].

JPG, also written JPEG, is twenty-seven years older. The Joint Photographic Experts Group published it in September 1992 under two designations at once: ISO/IEC 10918 and ITU-T T.81[3]. JPG divides the picture into square blocks and describes each of them with a discrete cosine transform, DCT for short, dropping some of the finest detail along the way. Each of the three colour channels gets eight bits, and the format stores no transparency at all[2].

What separates them day to day is availability. Every browser, every operating system and every graphics program opens JPG, and the JPEG committee still calls it the most dominant still image format around[3]. AVIF needs software from the last few years, and on Windows a separate add-on[4]. That is why an AVIF file often has to become a JPG before the program you work in will open it.

Drag your AVIF files onto the Add files field, or click it and pick them from your device. Use the Set JPG quality slider to choose a value between 60 and 95 per cent; it sits at 85 by default. Click Convert and every item in the queue on the right turns to a green Done badge.

There are two ways to collect the results. The Download button next to an item saves that one file, while Download all saves the whole queue. The name stays the same and only the extension changes to .jpg. Clear all empties the queue when you want to start over.

Under the buttons the converter reports Total input size and Total output size, with the difference between them below. You see the same figures per file, in the Before and After lines.

Both formats store pictures lossily, throwing away part of the information so the file takes up less room. They go about it differently. JPG uses a method described in 1992[3], while AVIF uses the tools of the AV1 codec, which arrived more than a quarter of a century later and describes the same picture in fewer bytes. MDN states the gap plainly: at similar visual quality an AVIF file is around half the size of a JPG[2].

So the weight goes up. Your file is already stored by the thriftier method, and the converter unpacks the picture into a full grid of pixels and writes it again with the older one. At the default 85% quality we measured growth of 1.8 to 3.5 times. The exact figure depends on the picture: the more large, even areas it holds, the bigger the gap, because those areas are precisely what the AV1 codec stores most efficiently.

The quality slider is what gives you control. Setting it to 60% brings the result down to 1.1–2.5 times the weight of the source, and the difference then shows up mostly on flat surfaces such as a clear sky. If you want the lightest possible file and the person receiving it accepts other formats, the same picture ends up smaller with the AVIF to WebP converter.

Transparent areas are filled with white. JPG has no alpha channel, so every pixel has to be given a definite colour, and white suits most uses. We checked this on a graphic with a transparent background: a pixel described in the AVIF as fully transparent comes out of the JPG as clean white. When the background has to stay transparent, use the AVIF to PNG converter.

EXIF data does not carry over to the output file. EXIF is the record that a camera or phone attaches to a photograph: the device model, the exposure time, the date and, with location switched on, the coordinates of the place the picture was taken. We measured this on an AVIF file with a record deliberately written into it, and the resulting JPG holds no trace of it. What remains is the picture itself with an sRGB colour space description, so a photo you pass on no longer carries information about where and with what it was taken.

A single file can weigh up to 100 MB. Pictures wider or taller than 16,384 pixels, and those holding more than 268 million pixels in total, are scaled down proportionally to that limit before they are saved. This affects panoramas and large-format scans; an ordinary photograph from a camera or a phone sits well inside the range.