Step 1: Provide your AV1 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 WebM files.
AV1 to WebM Conversion FAQ
How do I convert AV1 to WebM 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 WebM container without re-encoding it, MKV to MP4 among them, which is quick and loses no quality. Most pairs re-encode the video. AV1 is a codec, not a container — the bitstream normally travels inside MP4 or WebM, paired with Opus or AAC audio. WebM is deliberately narrow: VP8 or VP9 video (AV1 more recently) with Vorbis or Opus audio, and nothing else.
My AV1 has several audio tracks — do they all survive into the WebM?
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No. The converter keeps one audio track, the one with the most channels (normally the main mix), and drops the rest; there is no setting to pick a different one. To keep another track, remux the AV1 with that track first (VLC or ffmpeg can do this), then convert it. AV1 delivers roughly 30% better compression than H.264 at the same quality and carries no licence fees, which is why YouTube and Netflix push it. WebM is a poor fit anywhere outside a browser — video editors, phones’ native galleries and Smart TVs largely ignore it.
Is WebM a container or a codec, and does that change what I get back?
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It changes what to expect from the output file. One side of this conversion names an encoding rather than a wrapper, so what comes back is that bitstream inside whichever container suits it best — normally MP4 or MKV. The extension reflects the container; the codec is what actually determined the file size and where it will play.
Will multi-track audio survive AV1 to WebM 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 WebM 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 AV1 with that track first (VLC or ffmpeg can do this), then convert it. WebM is a strict subset of Matroska that Google published in 2010 specifically to give HTML5 video a royalty-free container.
Are subtitle tracks preserved when converting AV1 to WebM?
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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 AV1 to WebM?
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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 AV1 to WebM drops these attachments when WebM is not MKV — the elementary streams convert, but the attached payload stays in the source. Keep AV1 as a backup if you depend on attached fonts.
Which codec does the WebM output use by default?
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It depends on the WebM 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. 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.
How does HDR (HDR10, Dolby Vision) survive AV1 to WebM?
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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 AV1 can look washed out in the WebM.
Why is my WebM file smaller / larger than the AV1 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 AV1 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 AV1 to WebM 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.
