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 wraps 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 result keeps AV1 or gets re-encoded 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 stream can go in as-is — without being re-encoded — if you choose to keep it. 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 (re-encoded); pick AV1 instead to keep the original stream inside the WebM container with no quality loss.
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 existing coded video is wrapped into WebM with no re-encoding and no generational quality loss. This is the fastest, highest-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 again as VP9. You lose a little quality and it 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 and you want a remux of that file 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.

Frequently Asked Questions

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

Either, depending on the Video Codec you pick. Select AV1 and the existing stream is wrapped into WebM with no re-encoding and no quality loss. Leave the WebM default of VP9 and the video is decoded and re-encoded, which costs a little quality but plays on more browsers and older devices. The dropdown is where you make that call.

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 an AV1 stream in WebM rather than re-encoding it 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

In your testing, does choosing AV1 actually avoid a re-encode?

In our testing, selecting AV1 as the Video Codec on a clean raw .av1 stream produces a WebM whose video matches the source frame-for-frame, with no re-encoding step — the conversion finishes faster and the picture is identical to the input. Switching the codec to VP9 triggers a full re-encode, which takes longer and is visibly a transcode rather than a wrap.

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