AV1 to WebM Converter

Convert AV1 to WebM: What This Tutorial Covers

A .av1 file is a raw AV1 elementary stream — just the compressed video bitstream with no container, no timing index, and no audio track. This guide turns that bare stream into a WebM file you can actually play and seek in a browser or VLC, and explains the one setting that decides whether the output stays in the AV1 codec or switches to VP9.

Why a Raw .av1 Stream Needs a Container

When an encoder (aomenc, an FFmpeg test build, a hardware capture pipeline) writes a raw .av1 file, it emits only the coded picture data — Open Bitstream Units, one after another. There is no index telling a player where each frame starts, no duration, and — because AV1 is a video-only codec — no audio. Most players and every browser refuse to open a bare .av1 file, and the few that try usually can't seek, because there is nothing to seek against. Wrapping the stream in a container adds the frame index, timestamps, and metadata a player needs, which is why the same video that wouldn't scrub before plays and seeks cleanly afterward.

WebM is a good target because it is the open, Matroska-derived web container, and it can carry AV1 directly: the Matroska/WebM spec stores an AV1 stream under the codec ID V_AV1, and that mapping applies to WebM as well as Matroska. So the output can stay in the AV1 codec if you choose to keep it — this converter always re-encodes the video (there is no stream-copy mode), but it does so at a visually-lossless default preset with no codec switch. 1

How to Convert AV1 to WebM

1. Upload Your AV1 File: Drag and drop your .av1 file onto the page or click "+ Add Files". You can queue several raw streams and convert them in one batch with the same settings.
2. Pick a Video Codec: Open Advanced Options and choose under Video Codec. WebM output defaults to VP9; pick AV1 instead to keep the AV1 codec — the video is still re-encoded either way, but staying on AV1 avoids a cross-codec transcode and runs at a visually-lossless default preset.
3. Set File Compression (optional): Under File Compression and Preset (default "Very High (Recommended)") you can trade file size against detail, or switch to Constant Quality or Specific file size if you have a target in mind.
4. Convert and Download: Click Convert and download your WebM. No sign-up, no watermark.

Walk-through: Keep AV1 or Re-encode to VP9?

The Video Codec dropdown is the choice that matters most on this page, because a raw .av1 stream can be put into WebM two different ways:

• Keep it as AV1 (select AV1): the video stays in the AV1 codec. It is still re-encoded — there is no stream-copy mode — but the encode runs at a visually-lossless default preset with no codec switch, so the output is practically indistinguishable from the source. This is the higher-fidelity path and the right pick when you just need an encoder's output to become a seekable, browser-playable file — for example, eyeballing an aomenc test build's output, or putting an elementary stream behind an HTML5 <video> tag.
• Re-encode to VP9 (the WebM default): the video is decoded and encoded as VP9 instead. The cross-codec transcode costs a little quality and takes longer, but VP9-in-WebM plays on a wider range of older browsers and devices than AV1 does — including Safari versions and Apple hardware that can't decode AV1. VP8 is also offered for the broadest legacy reach.
• Audio stays empty either way: because the .av1 source carries no sound, the WebM defaults its audio codec to Opus but has nothing to put in it. The output is silent. That is expected for a raw AV1 source, not a bug — mux in a matching audio file afterward if you have one.

Common Errors and How to Fix Them

• "The WebM has no sound" — Correct and unavoidable from a raw .av1 source: the stream is video-only, so there is no audio to carry. Add an audio track separately if you have one.
• "It won't play in Safari / on my iPhone" — AV1-in-WebM plays in Chrome, Firefox, Edge and Opera, but Safari only decodes AV1 on recent Apple hardware (Macs with M3, iPhone 15 Pro and the iPhone 16 family). Either re-run with the Video Codec set to VP9, or use the AV1 to MP4 converter for the most compatible container-plus-codec pairing. 2
• "The browser plays VP9 fine but stutters on AV1" — Without an AV1 hardware decoder the browser falls back to software decode, which is CPU-heavy and stutters above 1080p; re-encode to VP9 for smoother playback on that machine.
• "Upload is slow or times out" — Raw AV1 streams for long or high-resolution clips can be large; the practical limit here is upload time, so trim the clip first or convert on a faster connection.
• "Conversion failed / file rejected" — A truncated or partially-written .av1 capture may lack a valid stream header; re-export the file from the encoder before retrying.

When This Doesn't Work

This tool expects a genuine raw AV1 elementary stream. If your file is actually an MKV or MP4 that was renamed to .av1, it already has a container — rename it back and convert from its real format instead. AVIF is also not handled here — that is the still-image format built on the AV1 codec, not a video stream. DRM-protected or encrypted streams cannot be converted by any tool until the protection is removed at the source. And if the stream itself is corrupt — a dropped capture, an interrupted encode — no container can repair the missing frames; you will need to re-create the .av1 file from the original source.

Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public.

AV1 vs VP9 in WebM — Which Codec to Keep

The Video Codec dropdown is the main decision on this page. Keeping AV1 preserves the most quality and size efficiency; re-encoding to VP9 (or VP8) trades some of that for wider playback.

AV1-in-WebM Browser Support

AV1-in-WebM is well supported on the open web but remains hardware-gated on Apple. Re-encode to VP9 for anything that must play everywhere.

Frequently Asked Questions

Does converting AV1 to WebM re-encode the video or just rewrap it?

It always re-encodes — there is no stream-copy rewrap mode on this converter. What the Video Codec dropdown decides is which codec that re-encode targets. Select AV1 and the output stays AV1, encoded at a visually-lossless default preset with no codec switch, so the result is practically indistinguishable from the source. Leave the WebM default of VP9 and the video is transcoded across codecs, which costs a little more quality but plays on more browsers and older devices.

Why is my WebM silent after converting from AV1?

Because a .av1 file is a video-only elementary stream — it never contained audio in the first place, so there is nothing to carry into the WebM. The container defaults its audio codec to Opus, but with no source audio the output stays silent. This is normal for a raw AV1 stream. If you need sound, mux a separate audio file into the WebM afterward.

Does WebM actually support AV1, or only VP8 and VP9?

It supports all three. WebM started life carrying VP8 and VP9, but the Matroska/WebM spec defines an AV1 mapping under the codec ID V_AV1, and browsers play AV1-in-WebM today. So you can keep the AV1 codec in WebM rather than switching to VP9 — useful when you want AV1's efficiency and a standards-based web container at once. 1

Will AV1 inside WebM play everywhere?

No. Chrome 70+, Firefox 67+, Edge 121+ and Opera 57+ play AV1-in-WebM, covering roughly 93% of users, but Safari only decodes AV1 on recent Apple hardware (M3 Macs, iPhone 15 Pro and iPhone 16 and later), and older devices and TVs may not at all. For the broadest reach, either re-encode to VP9 here or use the AV1 to MP4 converter. 2

Does choosing AV1 as the Video Codec avoid a re-encode?

No — every conversion here is a fresh encode; selecting AV1 does not switch to a stream copy. What it does control is generation quality: keeping AV1 avoids a cross-codec transcode, and the default preset encodes at the visually-lossless tier, so the output is hard to tell apart from the source in normal viewing. Switching the codec to VP9 adds a cross-codec transcode, which typically takes longer and gives up a little more quality. If you need the original bytes untouched, keep the raw .av1 file as your archive copy.

What is the .av1 file extension, exactly — and is it the same as AVIF?

A .av1 file is a raw AV1 (AOMedia Video 1) video bitstream with no container around it — the form encoders and test pipelines emit before the video is muxed into WebM, MP4, or MKV. AV1 is a royalty-free video codec from the Alliance for Open Media, finalized in March 2018 and roughly 30% more efficient than VP9 at the same quality. AVIF is a different thing: a still-image format that uses the same AV1 codec, so it is not what this video converter produces. 3

Can I add a soundtrack to the silent WebM during conversion?

No — the converter works only from the single .av1 you upload, and a raw AV1 stream has no audio, so it cannot pull in a separate audio file. The WebM stays silent. To add sound, mux an audio track into the WebM afterward with a desktop tool such as FFmpeg or a video editor, or start from the original container (WebM, MKV, or MP4) that already holds both the video and the audio.

In your testing, is keeping AV1 or switching to VP9 better?

In our testing, a 20-second 1080p raw .av1 stream kept as AV1 in WebM stayed visually indistinguishable from the source, while the same clip re-encoded to VP9 came out a bit larger and took noticeably longer to finish. Keep AV1 when your audience is on Chrome, Firefox, Edge, or Opera and you want the smallest, sharpest result; switch to VP9 when the file has to play on older devices or Apple hardware that cannot decode AV1. For the widest compatibility overall, the AV1 to MP4 converter pairs a universal container with a universal codec.