Dummy WebP File Generator
Every dummy WebP file is a valid lossy WebP image at the width and height you pick, exact to the byte.
Sample WEBP files, ready to download:
One click, exact size (1 KB = 1,024 bytes), default options, built in your browser.
A dummy WebP file is a valid lossy WebP image made for testing, decoded by browsers at the width and height you choose (800 x 500 by default). Download one free at the exact size you need, from 576 Bytes to 50 MB. WebP is the image type most likely to bounce off an upload filter written for JPEG and PNG, so it deserves a test of its own. Run the same test with a dummy PNG file and you will know whether your app treats both formats alike.
How we check it: every generated file must be exactly the size you set and pass a decode in headless Microsoft Edge at the chosen width and height, plus our own WebP RIFF chunk checks; the last browser run on 21 October 2026 passed 520 of 520 cases (how the files are made and checked).
What is inside a dummy WebP file
The image data comes from your browser; the container is rewritten so it can carry padding (how we build and check these files):
- A lossy WebP image encoded by your browser at quality 0.92, at exactly the width and height you chose, with the same badge graphic as the other dummy images.
- The extended WebP layout: a VP8X header chunk that states the canvas size, then the image data, then a JUNK chunk that holds the extra bytes. JUNK is the RIFF container's own padding chunk, and WebP readers skip it.
- RIFF chunks always have an even length. For an odd file size, one zero byte follows the RIFF data; browsers and libwebp ignore it.
- WebP is the smallest of the image formats here (often under 10 KB at the default size), which helps when you need a tiny but valid image.
What a dummy WebP file is used for
Upload allow lists
See whether image/webp is on the list. Plenty of filters were written for JPEG, PNG and GIF and never updated.
Conversion and fallback
If your app converts WebP to JPEG for older clients or email, feed it WebP files of several sizes and check the output.
Media libraries
Upload WebP into a CMS or shop backend and confirm that thumbnails, previews and the original download all work.
Size limits
Generate WebP files one byte under, at and over your limit with exactly the dimensions you want.
Test whether your upload limit and filter accept WebP
Check the type before the size. Upload one small dummy WebP file first: if it is rejected, your filter does not allow WebP and the size limit has not even come into play. Once it passes, make three files around your limit, one byte under, at and over it.
Browsers send WebP as image/webp. On the server, image libraries need WebP support built in before they can read or resize it, so a WebP that uploads fine can still fail at the thumbnail step. Watch the logs, not just the upload response.
| Limit | Size | Notes |
|---|---|---|
| nginx client_max_body_size (default) | 1 MB 1,048,576 B | Requests with a larger body get HTTP 413. |
| PHP upload_max_filesize (default) | 2 MB 2,097,152 B | Also capped by post_max_size, so raise both. |
| AWS Lambda synchronous invocation payload | 6 MB 6,291,456 B | Applies to request and response. |
| Amazon API Gateway REST API payload | 10 MB 10,485,760 B | Hard quota for REST APIs. |
| Outlook default attachment limit (Exchange accounts) | 10 MB 10,485,760 B | Administrators can change it. |
| Outlook attachment limit (internet accounts) | 20 MB 20,971,520 B | Per Microsoft Outlook guidance. |
| Gmail message size limit | 25 MB 26,214,400 B | Attachments grow about a third when encoded, so a 20 MB file can already be too big. |
Lossy, lossless and animated WebP
This page makes still, lossy WebP images without an alpha channel. It does not make lossless or animated WebP. If your code has separate branches for those variants, test them with your own files as well.
WebP file details
- Extension
- WEBP .webp
- MIME type
- image/webp
- Smallest size
- 576 Bytes
- Largest size
- 50 MB
- Contents
- Lossy WebP image at the width and height you choose (default 800 x 500); extra size is a JUNK padding chunk inside the RIFF container
Dummy WebP file FAQ
Is the dummy WebP file valid?
Yes. It decodes in Microsoft Edge at the requested dimensions, and our checker walks the RIFF container, the VP8X header and every chunk size.
Which browsers can open WebP?
Current versions of Chrome, Edge, Firefox and Safari all display WebP. Some older desktop image viewers and very old browsers do not.
Can I set the width and height?
Yes. Open Options and set them in pixels, from 1 to 8,192; the default is 800 x 500. If the size is too small for the dimensions you chose, the tool tells you the minimum.
How is the exact file size reached?
The extra bytes go into a JUNK chunk inside the RIFF container, which readers skip. An odd size gets one extra zero byte after the RIFF data.
Is the WebP animated or transparent?
No. It is a single still frame, lossy, with no alpha channel.
How large can a dummy WebP file be?
Up to 50 MB. The dimensions go up to 8,192 x 8,192 pixels; very large ones may fail on phones.
Is the file uploaded to a server?
No. Your browser encodes it locally and nothing is sent anywhere.