Introduction

Just as automatically sending modern formats should be expected, we also expect that those using browsers that don’t support modern formats do not get an unnecessarily broken experience. If a WebP/AVIF image is explicitly requested, but would not be able to be rendered based on the Accept header, then the response should be “downgraded” to a supported image format.

The Test

Does an explicit request for a JPEG automatically respond with a WebP/AVIF image based on the Accept header?