Chrome saved a WebP and the form rejects it

The response format can differ from the URL

A URL ending in .jpg does not guarantee that the server returns JPEG. An image service can negotiate WebP from the browser's Accept header and return Content-Type: image/webp. Cloudflare Polish documents this behavior when its WebP option and other conditions apply.

The saved filename and response can therefore use WebP while the URL keeps its old suffix. The exact download name also depends on the server and browser. Check the actual file type instead of treating the URL as a format guarantee.

The same URL hands a different file to each browser

A server using content negotiation can return different formats for different requests. Trying another browser does not guarantee JPEG: its version and the server configuration matter. Use a converter when you need a definite output format.

This is why the usual tricks miss. Reloading, a hard refresh, opening the image in its own tab, or adding a query string to bust the cache all still go out with the same Accept header, so the same WebP comes back. The bytes you already downloaded are the ones you have to work with.

Confirm the file really is WebP

Windows' Type of file label can follow the extension, so it is not a reliable header check after renaming. Open the image in a compatible viewer or inspect it with a tool that identifies the data. Renaming WebP to JPG does not convert it.

On a phone the gallery previews it without complaint, which makes the upload failure feel random. It is not random: the gallery has a WebP decoder and the upload field has a list of extensions it was given years ago.

Convert to JPEG

WebP to JPG takes the file as it downloaded. If the image had transparency, pick a fill colour first, because JPEG has no transparency and something has to sit behind the logo.

1. Drop the .webp. Up to 10 files, 20 MB each.
2. Pick a fill if the image had transparency, then download JPEG, or a ZIP for several.
3. If the form also names a cap, follow with Compress JPG or a 200 KB target.

The upload field will never mention WebP

The error you get is usually just invalid file type, with no list of what would have worked. Behind it is an allowlist written when WebP was a Google experiment. An Etsy listing photo, a benefits portal document upload, and an old HR attachment field all behave the same way and none of them will be updated because you asked.

So read the accepted formats on the form before you troubleshoot your browser. If JPG, JPEG, and PNG are the three entries, that is the answer, and no browser setting on your side changes it.

When PNG is the right target instead

Transparency that has to stay transparent goes through WebP to PNG. A logo grabbed off a site is often a WebP with an alpha channel: flattening it onto white looks correct on a white page and turns into a sticker in dark mode.

Interface screenshots with small text also survive better as PNG than as JPEG, where letter edges pick up a halo. Why that PNG then weighs so much is PNG too large.

The JPEG comes out bigger, and that is expected

The JPEG may be larger or smaller depending on dimensions and quality settings. Conversion to JPEG is a new lossy export, so compare small text and edges before using it. Keep the WebP source if you may need another output later.

Chrome saves AVIF the same way

Same negotiation, newer codec. The site answered with image/avif and the download landed as .avif. AVIF to JPG writes a standard JPEG, HDR flattens to 8-bit, and transparency needs a fill exactly as it does here.

AVIF on Windows covers the Store package if you would rather preview than convert. And if you are gathering images for a site of your own, keep them modern: JPG to WebP and PNG to WebP go the other direction.

Related guides: listing photo size.