Create an MP4 container upload fixture
Choose a size for a fixture with ftyp and free boxes. It has no moov box or video track; use a playable video for codec and playback tests.
1 MB = 1,000,000 B · 1 MiB = 1,048,576 B
Advanced: test an upload limit
Enter the byte limit above, then choose one byte below, the exact limit or one byte above. Each choice uses the same base: 10,485,760 B. Generate and download each file to test your endpoint.
MP4, built to spec.
Each file is an ISO Base Media container with correct ftyp branding. The size you ask for is reached with a free box, the container’s own reserved-space atom, so the result opens in container parsers and ffprobe — note it carries no video track, so it will not play. Most people generate these for testing upload size limits where playback is not required.
Choose a size here
These options set the generator above. Separate size guides explain how to test a particular upload boundary.
Guides for specific upload limits
File structure and testing limits
This fixture contains ftyp and free boxes, with no moov box or video track. It is unsuitable for playback, codec or video-duration tests.
Format reference: MP4 Registration Authority.
This generator assembles the file in your browser; file content is not sent to a server. Site analytics may make network requests. Office ↔ PDF conversion uses a separate server workflow. Data processing and privacy.
Technical notes for every format · Guide to testing file upload limits
Questions
How small can an MP4 file be?
About 48 bytes. Below that the format cannot carry its mandatory structure, let alone padding.
Will the file open normally?
Validate the generated fixture in your target application. Parts added for exact size may change or disappear when the file is re-saved; compatibility depends on the reader.
Can I ask for an unusual size?
Any byte count above the minimum works — for example 3,145,728 bytes (exactly 3 MB) or 27.5 MB. Drag the caliper or type the number.
Noticed an issue with this test file? Report an issue →