What is a WebP file, and why did my image save as one?

Downloaded a WebP when you expected a JPG? WebP is an image format websites use to send smaller pictures; you need to convert it when your app asks for something else.

FluffyBench · 5 min read · Reviewed October 15, 2026

What is a WebP file?

WebP is an image format: a way to store a picture's information in a file, just as JPG and PNG are. It can hold a photo, a drawing, see-through areas, or an animation. So finding .webp on a downloaded picture doesn't mean you've downloaded the wrong thing.

Think of an image file as a package. The picture's information is inside; the filename ending is a tag telling an app what to expect.

A flower stored as WebP inside a file, with picture.webp on a separate filename tag. — The filename labels the package; the image format describes its contents. How we reviewed

Why did a website send WebP from a JPG link?

Websites use WebP because it can make pictures smaller to send without making them look much different. The site may keep several versions of a picture and choose one your browser can display. That choice happens while the page loads; you don't need to request a WebP yourself.

A JPG-looking address tells your browser where to ask for a picture. A website can answer that request with WebP, so the saved copy can be WebP too.

A browser requests picture.jpg and says it can display WebP. The website returns image/webp, and the saved file is picture.webp. — The requested address and the returned image format can differ.

Why doesn't renaming WebP make it a JPG?

Changing picture.webp to picture.jpg changes the package tag, not the picture inside. In this real example, FluffyBench's JPG to PNG refuses the renamed WebP; FluffyBench's Any image to PNG recognizes the same contents.

picture.jpg refused with That file does not contain a valid JPEG header. — Both captures use the same renamed WebP; apps can check what's inside the file.

The same picture.jpg recognized and converted, with Done beside its PNG output. — Both captures use the same renamed WebP; apps can check what's inside the file.

If someone has already changed the ending, FluffyBench's Any image to PNG can read the contents and make a PNG copy. A conversion writes the image in the new format, which is what a destination that asks for JPG or PNG needs.

Can you use WebP, or do you need JPG or PNG?

The app or website where you'll use the picture decides whether conversion is useful. If it opens your WebP, you're done; if it asks for a different format, make that copy.

Decision path: if your destination opens WebP, keep it. If it does not, convert to the JPG or PNG format it requests. — Match the destination's format requirement, instead of converting every WebP you download.

If you're wondering about viewing WebP on the web, the browser image-format guide covers that question.

JPG fills see-through areas with a solid color. For a clear background, FluffyBench's WebP to PNG keeps transparency with PNG encoding left on Browser default, as in the right-hand copy below.

The source WebP flower with checkerboard visible in its clear corners. — Matched flower crops rendered for illustration; the checkerboard marks clear areas.

The same flower saved as JPG with white corners covering the checkerboard. — Matched flower crops rendered for illustration; the checkerboard marks clear areas.

If your WebP moves, FluffyBench's JPG and PNG outputs keep its first frame. When you need the movement, use the animation conversion guide to choose a format that keeps the animation.

Doing it in FluffyBench

For a destination that asks for JPG, open FluffyBench's WebP to JPG. For a PNG requirement or a clear background, open FluffyBench's WebP to PNG. Each link opens with that output already chosen.

Here's the WebP-to-JPG job in FluffyBench, using the flower above. Keep the original WebP alongside your converted copy.

Step 1. Add the WebP you want to convert.
1. Choose images opens your file picker.
Step 2. Open the JPG settings before converting.
1. Open Settings to see the fill color.
Step 3. Use the default White fill for the JPG pictured above.
1. Leave Fill color on White.
Step 4. Create the JPG copy with these settings.
1. Press Convert 1 to JPG.
Step 5. Check the picture and output size, then save your JPG copy.
1. Check the petal edge and background.
2. Read the output size on the second line.
3. The download arrow saves the JPG.

The PNG route uses the same Choose images, Convert and download controls. Your destination app is the final check: the saved picture needs to open there, look right and meet any upload-size limit. Converting won't bring back detail a smaller, lossy image has already discarded.

FluffyBench's Image Viewer opens a WebP without converting it.

Image Viewer

How we measured

Date: October 15, 2026. Browser: Chrome 153.0.8010.12. Device: AMD Ryzen 9 5950X, Windows 11 Pro.

FluffyBench's WebP converter at its default quality and at its lossless setting, and FluffyBench's JPG converter at its default quality. No resize was applied.

One first-party 640 × 480 flat screenshot sample, converted to lossy WebP, lossless WebP and JPEG.

File sizes are exact bytes; offsets are counted from the start of the file.

FluffyBench's WebP converter wrote the lossy file at 1,994 bytes and the lossless file at 188 bytes for the same pixels.

The earlier byte review used a 23,936-byte WebP written by FluffyBench's PNG to WebP converter; its size field reads 23,928 bytes, which is the file size minus the 8-byte RIFF header. The JPEG comparison is the first line of the real screenshot.jpg (8,029 bytes) from the same run.

Format behavior was checked against the linked Google WebP documentation and container specification, MDN's content-negotiation and image-format guides, the ITU-T T.81 JPEG standard and Cloudflare's Polish documentation.

Google's size comparisons are the vendor's own general claims for comparable files, not a result measured on this page.

The flower comparison and walkthrough were rendered for illustration on October 23, 2026 from the first-party flower WebP used in the transparency guide. FluffyBench WebP to JPG used the default quality, Standard encoder, white fill and Original size; WebP to PNG used Browser default and Original size. Matching crops cover the same source region. These illustrate transparency, with no size or quality comparison claim.

The renamed-file captures were taken on October 19, 2026 at device pixel ratio 2 from the local FluffyBench converters; the displayed crops retain the filename and result. They show interface behavior only; no new benchmark values are reported. The renamed input is a first-party tools screenshot saved as WebP.