WEBP and AVIF get lumped together constantly as "the two modern image formats," as if picking between them is a formality. It isn't quite that simple, and running an actual file through the conversion is more informative than trusting the reputation either format has picked up. Here's how the two actually compare across the things that matter, tested rather than assumed.

Round one is compression, and the result surprised us. AVIF is built on the AV1 video codec, a newer and generally more efficient compression engine than the VP8 codec WEBP is built on, so the expectation going in was a meaningful size drop. We ran a real WEBP file through the converter to AVIF and got barely anything: a 1% reduction. Not the 20 to 30% improvement AVIF's reputation would suggest. The reason comes down to what you're actually testing. AVIF's efficiency advantage shows up clearest when encoding from an uncompressed or lightly compressed source, where the encoder has real redundancy to work with. A WEBP file has typically already been through a solid compression pass. Feeding an already-compressed file into a second, newer compressor doesn't uncover a second round of savings sitting there waiting; most of what could be squeezed out already has been. If you're chasing file size specifically, converting straight from an original PNG or JPEG source to AVIF will get you a real result. Going from WEBP to AVIF mostly won't.

Round two is what AVIF can technically hold that WEBP can't, and this is where the marketing tends to get ahead of what actually applies to most files. AVIF supports higher bit depth, up to 10 or 12 bits per channel instead of WEBP's 8, along with wide color gamut and HDR. That's a real capability of the format. It is not something a conversion tool can retroactively add to a file that never had it. If the WEBP you're converting was created from an 8-bit standard-range source, which the overwhelming majority of web images are, converting it to AVIF doesn't unlock extra tonal range or color depth from nowhere. The AVIF file inherits exactly what the WEBP had to offer, nothing more. That advanced capability only matters if it's baked into the source before WEBP ever entered the picture, which for most everyday images it isn't.

Round three is compatibility, and this is the one place the trade genuinely runs backward. WEBP support is close to universal at this point, essentially every current browser and a wide range of software handles it without a second thought. AVIF's support is real but younger and narrower: some older devices, some image editors, and a handful of platforms still don't handle it cleanly. Converting a working, broadly compatible WEBP file into AVIF trades a format that reliably displays everywhere for one that occasionally doesn't, in exchange for a compression gain that, per the test above, may not even be meaningful in your specific case.

Put together, none of this argues against AVIF as a format. It argues against assuming WEBP to AVIF is an automatic upgrade just because AVIF is newer. The conversion earns its place when you specifically need AVIF's newer capabilities for a source that actually carries that data, or when a particular platform requires AVIF outright. For a WEBP file that's already doing its job well, running it through this WEBP to AVIF converter is worth doing to see the real numbers on your own file before deciding whether the switch is worth the trade-off, rather than converting on the assumption that newer automatically means smaller. The same tool's format dropdown covers the reverse direction and every other destination too, JPG, PNG, SVG, JFIF, GIF, ICO, and TIFF, in case AVIF turns out not to be the answer once you've actually looked at the numbers.