Introduction

AV1 Image File Format (AVIF) is a newer image file format. The first version of the AVIF specification was published in February 2019, and started to be widely supported in modern browsers in 2021.

The Test

Ideally, if a JPEG is requested with an Accept header that includes image/avif, it will return an AVIF image.

An example of checking for AVIF using curl would look like this

$ curl 'https://cdn.example.com/imnage.jpg' \
  -H 'accept: text/html,image/avif' \
  -L -so output_image

From there, we check to see what the format of the returned image is.

$ file output_image
output_image: ISO Media, AVIF Image

However, not all services offer respect accept headers, despite offering the image formats. In this case, they are manually set to Pass