Why is AVIF not enabled by default?

For ImageEngine it is important to always serve the best image determined by

• Byte size
• Visual quality
• Encoding efficiency
• Decoding efficiency

Our tests show that AVIF is in most cases outperformed by WEBP and other formats.

While maintaining a good visual quality on AVIF images, the difference in byte size compared to WEBP is negligible.

AVIF encoding efficiency is also significantly lower compared to WEBP. More resource intensive and slower.

Even decoding an AVIF image on the end users' devices is slower and more resource intensive compared to WEBP.

The conclusion is that, in most cases, WEBP will display the image on the end users' devices faster, with better visual quality, and with a lower resource footprint.

Knowing that AVIF is supported by the same browsers and devices which supports WEBP, AVIF would rarely be selected as the best format by the ImageEngine algorithm if AVIF was included in the chain of image formats.

The future of AVIF

For the above reasons, we've concluded that AVIF is still too immature to be included in the conversion chain in the same manner as other formats.

Because ImageEngine is a fully automatic Image CDN, where the optimization algorithm has to make decisions real time, AVIF is still too immature and doesn't offer the encoding efficiency and image quality needed.

AVIF is better used in offline or batch workflows where parameters can be tweaked and tested before the image is published. In these scenarios it is likely that AVIF will produce better results than WEBP (generally about 20%-30% lower byte size). However, for a real time Image CDN this is currently not an option.

We will keep monitoring the performance of AVIF and once the encoders and decoders are mature enough, AVIF will be supported the same way as any other image format.

Until then, AVIF can be enabled as the preferred image format, or enabled through directives.