Free WEBM test files and sample generator
Open, royalty-free video container designed for the web (VP8/VP9/AV1).
What is a .webm file?
WEBM: WebM Video. WebM is the open web video container, built on Matroska with VP8 or VP9 video. Browsers can both play and record it, which is why it is the natural output of in-browser capture.
Why generate a test WEBM file?
- Test video upload and playback for open formats.
- Verify handling of browser-recorded media.
- Check duration and size validation.
What you can put inside a .webm file
You get 3 content options for WEBM, so the file holds something meaningful rather than random padding: Color bars, Timer / counter, Logo motion. For WEBM these are alternatives, so choose the one that matches what you need to test.
How a .webm file is identified
Every .webm file begins with 1A 45 DF A3, an EBML header, WebM and Matroska share it, and differ only in the DocType inside. That is what a validator inspecting content rather than the file name looks for.
How the size lands on the exact byte
Matroska defines a Void element that readers skip, so the padding goes there after the browser has finished recording.
Negative testing with broken WEBM files
- Invalid. Identifiable, but wrong inside, so it fails during parsing.
- Corrupted. The leading bytes are destroyed, so the
1A 45 DF A3identifying a .webm is gone. Same length as the valid file. - Incomplete. Truncated part-way, so it is genuinely shorter.
- Empty. Chosen under Content rather than File Condition: valid structure, no data.
Which failure to reach for, and what to assert for each, is covered in how to make a corrupted file for testing. For upload limits and type checks see testing file upload validation.
Sample WEBM content
[Binary video], 1080p, VP9, Opus audio.
This shows the shape of the file. Your download is generated fresh at the size you choose, so the values will differ.
How to open and verify the file
Play in Chrome, Edge or Firefox, or in VLC; inspect with `ffprobe`.
Media type video/webm · extension .webm · category Video
Generate a .webm file → · questions about sizes, privacy or cost are answered on the site FAQ.
Frequently asked questions about WEBM files
What identifies a .webm file?
A .webm file begins with the bytes 1A 45 DF A3, an EBML header, WebM and Matroska share it, and differ only in the DocType inside. Those bytes are what a content-sniffing validator looks for, and what the Corrupted condition destroys.
How can a .webm file be an exact number of bytes?
Matroska defines a Void element that readers skip, so the padding goes there after the browser has finished recording.
What can go inside the WEBM file?
There are 3 content options for .webm: Color bars, Timer / counter, Logo motion. For WEBM these are alternatives, so pick the one matching what you need to test.
Can I download several broken WEBM files at once?
Yes, select more than one File Condition and you get one ZIP containing a .webm per condition, each named after its condition.
Can the WEBM file use UTF-16 or a byte-order mark?
No, and deliberately. A .webm file is a container rather than plain text, so rewriting its bytes as UTF-16 would not produce a UTF-16 document. It would produce a broken file. Use a text format such as CSV, JSON or XML for encoding tests.
How do I open or verify the WEBM file?
Play in Chrome, Edge or Firefox, or in VLC; inspect with ffprobe.