Step 1: Provide your WebM files using the button above or by toss and let go.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Fetch your converted MP4 files.
WebM to MP4 Conversion FAQ
How do I convert WebM to MP4 without re-encoding the video stream?
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There is no stream-copy switch on this page. A few pairs copy a compatible video stream into the MP4 container without re-encoding it, MKV to MP4 among them, which is quick and loses no quality. Most pairs re-encode the video. WebM is deliberately narrow: VP8 or VP9 video (AV1 more recently) with Vorbis or Opus audio, and nothing else. Almost every MP4 in the wild is H.264 video with AAC audio; the container also legally holds HEVC, AV1 and VP9.
Both WebM and MP4 are modern containers — which should I actually keep?
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Keep whichever matches where the file is going, because neither is better in the abstract. One of these two is built for playback compatibility and the other for holding everything a file might contain, and they trade against each other exactly along that line. The pragmatic answer for most libraries is to archive in the feature-rich container and export to the compatible one on demand. WebM plays natively in every modern browser with no plugin, no licence fee and no patent exposure, which makes it the default for web-embedded video. MP4 is the safest possible delivery target — every phone, browser, console, editor and Smart TV built in the last decade plays it without extra software.
Will multi-track audio survive WebM to MP4 conversion?
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Usually not. Most conversions keep one audio track, the one with the most channels (normally the main mix), re-encoded for the MP4 container, so commentary and alternate-language tracks are dropped. AVI, WMV, MPEG, FLV, VOB and M4V to MKV keep every track, and so does MP4 to MOV. To keep a different track, remux the WebM with that track first (VLC or ffmpeg can do this), then convert it. MP4 is ISO/IEC 14496-14, standardised in 2001 and derived from the same QuickTime box layout MOV uses.
Are subtitle tracks preserved when converting WebM to MP4?
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On some pairs. MP4 to MOV keeps every text subtitle track. AVI, WMV, MPEG, FLV, VOB and M4V to MKV keep every subtitle track: text subtitles are copied or converted to SRT, and picture-based subtitles such as DVD or Blu-ray ones are copied as they are. MP4, MOV and WebM to MKV keep only the first subtitle track (as ASS), and MP4 to WebM keeps the first one as WebVTT. Other pairs, including MKV to MP4 or MOV and WebM to MP4, drop subtitle tracks, and the converter does not burn them into the picture. Subtitles that are already burned in stay, because they are part of the video frames.
What about MKV attachments (fonts, cover art) when going WebM to MP4?
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MKV is the only mainstream container that stores arbitrary attached files (TTF fonts for ASS subs, JPG cover art, fan-translated PDF inserts). Going from WebM to MP4 drops these attachments when MP4 is not MKV — the elementary streams convert, but the attached payload stays in the source. Keep WebM as a backup if you depend on attached fonts.
Which codec does the MP4 output use by default?
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It depends on the MP4 container. MP4, MOV and MKV output use H.264, which plays on practically every phone, browser and TV. WebM output uses VP9. AVI, WMV and MPEG output use the older codecs those formats were designed for. MP4 only supports one widely-honoured subtitle format (mov_text), and multi-track audio is unreliable outside desktop players.
How does HDR (HDR10, Dolby Vision) survive WebM to MP4?
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There is no HDR processing or tone mapping. When the video stream is copied (MKV to MP4 or MOV with the default settings), HDR10 passes through as it is. When the video is re-encoded, the HDR10 mastering metadata is dropped and Dolby Vision or HDR10+ data is not kept, and with a Quality, Resolution or Frame Rate setting some pairs also reduce the video to 8-bit colour, so an HDR WebM can look washed out in the MP4.
Why is my MP4 file smaller / larger than the WebM after conversion?
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It depends on what happens to the video. MKV to MP4 or MOV with the default settings copies the video stream unchanged, so the size stays close to the source. Most other pairs re-encode it: a high-bitrate WebM usually comes out smaller, while an already heavily compressed one can grow. Smaller File under Quality gives the smallest output, and H.265 in the Codec setting (MP4, MOV and MKV) is usually smaller than H.264 at similar quality but plays on fewer devices.
Does the WebM to MP4 converter handle 4K / 8K / 60fps content?
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The converter has no resolution cap of its own; the limit is the upload size allowed on your plan, and 4K, 8K and 60 fps files keep their resolution and frame rate unless you change them. MKV to MP4 or MOV with the default settings copies the video stream, which is quick at any resolution. Other pairs re-encode on CPU and the time grows with the pixel count, so a long 4K or 8K file takes much longer than the same length in 1080p.
Is my WebM file private during MP4 conversion?
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Yes. Uploaded WebM files are processed on our own conversion servers, no person reviews them, and they are never shared. The upload and the converted MP4 are both deleted automatically about 24 hours after the conversion, which leaves time to download the result. See /privacy/ for the full policy.
