The upload form said "file format not supported" and your file is a .webp. Here is the fix: convert it to JPG with our WebP to JPG converter — it runs in your browser, nothing is uploaded to us, and you will have an accepted file in about a minute. The rejection is not about your file being broken. It is about the website's upload pipeline being old. Here is what is actually happening, and how to handle the variations.
Why websites reject WebP
Upload pipelines are conservative by design. When a site accepts your image, its server has to decode it — to resize it, thumbnail it, scan it. That decoding happens with libraries the site installed years ago, and the accept list was written at the same time. The usual suspects:
A format whitelist from the pre-WebP era. The form accepts .jpg, .jpeg, .png, .gif because that is what someone typed into the CMS config in 2014. Nobody has touched it since. This is the majority case — old WordPress installs, forum software, government and school portals, marketplace listing tools.
A server-side image library without WebP. Older GD builds and some ImageMagick installs were compiled without WebP support. Even if the form accepts the file, the processing step behind it cannot decode it, so the site rejects it up front.
Security scanning. Sane upload handlers check the file's magic bytes against an allowlist before storing anything. WebP's RIFF....WEBP signature simply is not on older lists.
The form's accept attribute. Sometimes the rejection happens in your own browser before anything is sent: the file picker greys out everything except the listed extensions. Same whitelist, closer to you.
WordPress deserves a special mention because it runs a huge share of the web. Its allowed types live in a MIME whitelist, and WebP uploads only became officially supported in WordPress 5.8 in 2021 — and even then, only if the hosting server's image library can decode them. Any older install, or a newer one on a host with an ancient GD build, rejects the file. If you run the site, the fix is a one-line filter. If you are just trying to upload a photo to it, conversion is the faster door.
The pattern underneath all four: the web serves WebP aggressively because browsers love it (the web image formats guide covers why), while the upload side of the same web still lives in 2014. You are standing in the gap between the two.
The fix: convert to an accepted format
Drop the WebP into the WebP to JPG converter, download the JPG, upload that. The conversion happens entirely on your device — the file never goes to our server or anyone else's — and the result passes every whitelist ever written, because JPG is on all of them.
If the rejection message complains about something after you convert — "file too large," "dimensions exceed limits" — the format was only the first gate. The size problem has its own tool: our image resizer scales the file down the same way, locally.
JPG or PNG: which one to convert to
Check the error message first — if the form lists its accepted formats, both JPG and PNG will be on it 99% of the time. Then pick by content:
- Photos, product shots, anything from a camera → JPG. Smaller file, and upload size limits are real. Transparency is impossible in JPG, but photos do not have any.
- Screenshots, logos, graphics, anything with text or transparency → PNG. Lossless edges and a real alpha channel; use the WebP to PNG converter and the transparent background survives intact.
When in doubt with a photo: JPG. The full quality walkthrough is in how to convert WebP to JPG.
The batch case: listings and catalogs
E-commerce sellers hit this constantly — a supplier sends a folder of product photos as WebP, and the marketplace only takes JPG. Converting one file at a time through a desktop app turns twenty photos into an afternoon. The browser converter takes the whole folder at once: drag the directory in, let it run, download everything as one ZIP. Filenames carry over, so your SKU naming survives the trip.
Related problems, other doors
If the WebP file never makes it to a website at all — it will not even open on your machine — that is the desktop version of this same support gap, covered in why you can't open WebP files. And if your downloads folder is filling up with WebP because Chrome keeps saving them, how to stop Chrome saving WebP handles the source side.
For the form that is rejecting you right now: convert the file, try the upload again, and the error message will be about something else or nothing at all — most likely nothing at all.