Convert PNG to AVIF

Both lossless and smaller

AVIF is the one modern format that offers both a lossless mode and a substantially smaller file than PNG. Lossless AVIF keeps every pixel exactly, and for a screenshot or a diagram it is usually smaller than PNG while looking identical. Lossy AVIF is dramatically smaller again and is what you want for a photograph. That two-mode choice is what makes this conversion worth considering rather than automatic.

NoteLossless AVIF is smaller than PNG for most content, but not all. Very simple images with few colours can be close to identical in size.

Choosing the mode by what is in the image

The rule is straightforward: keep lossless when the image contains text, hard edges, or flat colour areas that a human would notice being altered, and use lossy when it is a photograph. The reason is that AVIF lossy, like every lossy codec, is weakest exactly where those features are, and the artefacts appear as fringing around text edges and banding in smooth gradients. Lossless avoids all of that.

• Text, logos, diagrams: lossless. No artefacts, still smaller than PNG.
• Photographs: lossy at balanced quality. The saving is large and the difference invisible.
• Gradients: lossy AVIF usually looks smoother than PNG at the same file size.
• Flat colour areas: lossless, because lossy creates banding.
• When unsure, compare lossless against the original at 100 percent.

The fallback still applies

As with any AVIF file, a browser that cannot display it shows nothing rather than a fallback of its own. Serving AVIF therefore means keeping a WebP or PNG version alongside it, and keeping both costs storage and requests. That is a reasonable trade for a site where speed matters and the audience is current, and a poor one for email, for an older audience, or for a content system that will not accept the format.

• Keep a WebP or PNG fallback wherever you serve AVIF.
• Older browsers show nothing at all without a fallback, not a degraded image.
• Email clients: PNG or WebP is safer.
• Check the content system accepts AVIF before batch converting.
• Older design tools may not open AVIF at all.

Encoding time is the practical cost

AVIF is computationally expensive to encode, and that is felt in two places. A single image takes noticeably longer than a WebP conversion, which is usually irrelevant. A batch of a few hundred images can take long enough that it feels broken, especially on a phone. If you are converting a large set, expect to wait, and consider whether WebP would deliver enough of the saving for far less time.

• Single images are fine, the delay is brief.
• Large batches can take long enough to look like a failure.
• It is slower on a phone than on a desktop.
• WebP reaches most of the saving in a fraction of the time.