Convert MP4 to WebM Online
Choose a genuine video MP4. Each valid file starts its own conversion job when a compatible worker is available.
This page is shown in English because its translation has not been reviewed.
Choose MP4 videos
MP4 video · Each file starts a separate job · Up to 1 GiB per file
Checking for an available MP4 to WebM worker
Convert an MP4 video to WebM
Use this MP4 to WebM converter to create a WebM copy of a video for a browser or workflow that accepts WebM. MP4 and WebM are containers; the codecs inside a video affect which apps and devices can play it.
Choose genuine video MP4 files up to 1 GiB each. When a compatible healthy worker is available, each valid file starts its own upload and conversion job with separate progress, result, error, retry, and delete actions.
How MP4 is converted to WebM
WebM supports particular video and audio codecs. If all the MP4's video and audio streams are already compatible VP9 and Opus, the worker can copy them into WebM without re-encoding. Other supported video and audio streams are encoded using the worker's fixed VP9 and Opus defaults.
Re-encoding can change visual or audio quality. The worker checks the resulting file before making a signed download available; MP4 files with unsupported streams or characteristics can fail instead of producing a usable result.
A fixed conversion workflow
This page uses the worker's default conversion path. It does not offer controls for codec, bitrate, quality, audio settings, resize, or trim, and it does not promise that a WebM file will be smaller than its MP4 source.
A compatible VP9 and Opus stream-copy does not re-encode those streams. When encoding is needed, the conversion uses VP9 video and Opus audio; the output's quality and size depend on the source and conversion path.
Separate jobs and the 1 GiB file limit
Each selected MP4 gets its own worker selection, upload, progress updates, and output. A problem with one file does not change another file's job. The upload limit is 1 GiB per file; larger files must be reduced outside this converter before upload.
Download a completed WebM using its signed link, which expires within 24 hours. Use the delete action to remove the job files sooner.
How to convert MP4 to WebM online
- Choose one or more video MP4 files up to 1 GiB each.
- The page checks for a healthy worker that supports MP4 to WebM; each valid selected file then starts its own job.
- Follow each file's upload and conversion progress. Unsupported files or streams show an error rather than a usable download.
- Download the signed WebM when it is ready, or use the delete action to remove the job files sooner.
MP4 to WebM FAQ
Can I convert MP4 to WebM online?
Yes. Choose a genuine video MP4 up to 1 GiB. A compatible worker must be available, and files with unsupported content may fail.
Will converting MP4 to WebM reduce the file size?
Not necessarily. Compatible VP9 video and Opus audio can be copied without re-encoding; other supported streams are encoded with fixed VP9 and Opus defaults. The output may be larger or smaller than the source.
Can I choose video quality, codec, bitrate, or resolution?
No. This page runs a fixed MP4 to WebM workflow and does not expose quality, codec, bitrate, resize, trim, or audio settings.
Does the WebM keep every MP4 stream and detail?
Not in every case. The worker verifies the output, but some MP4 streams or characteristics are not supported and can cause conversion to fail. The page does not guarantee that every track or media detail will be preserved.
Can I convert an audio-only MP4?
No. This workflow requires a genuine video MP4 with a usable video stream. Audio-only files are not accepted.
How large can an MP4 file be?
Each MP4 upload can be up to 1 GiB. Reduce a larger video outside this converter before uploading it.
Can I convert multiple MP4 files?
Yes. Select multiple files and each valid MP4 starts an independent job with separate progress and a separate result. The 1 GiB limit applies to each file.
How long is the WebM download available?
The signed download link expires within 24 hours. Use the delete action to remove the job files sooner.