AV1 to MKV Converter

AV1 to MKV Converter

A .av1 file is a raw AV1 elementary stream — the coded video bitstream (Open Bitstream Units, or an IVF-wrapped variant) with no container, no seek index, and no audio track. Most players and every browser refuse to open a bare .av1, so it sits there unplayable. Wrapping that stream in an MKV (Matroska) container gives it the frame index, timestamps, and track structure a player needs, so the same video opens and scrubs cleanly in VLC, MPV, Kodi, Plex, or Jellyfin. This converter re-encodes the video into the MKV — there is no stream-copy or remux mode — and by default it targets the H.264 codec; you can switch the output to AV1 to keep the picture in the AV1 family.

The .av1 Format at a Glance

The MKV (Matroska) Format at a Glance

Choosing the MKV's Video Codec

Because the conversion always re-encodes, the Video Codec you pick decides what the finished MKV actually holds. MKV output defaults to H.264, so leaving the setting alone gives you an H.264 MKV, not an AV1 one.

How to Convert AV1 to MKV

1. Upload Your AV1 File: Drag and drop your .av1 file or click "Add Files". A .av1 file is a raw AV1 elementary stream (OBU or IVF), so it carries video only — no audio. Queue several streams to batch-convert them with the same settings.
2. Choose the Video Codec: MKV output defaults to the H.264 codec, so the AV1 video is re-encoded to H.264 unless you change it. Open Advanced Options and set Video Codec to AV1 to keep the picture in the AV1 family (still a fresh encode, not a stream copy), or to H.265, VP9, MPEG-4, or XviD for other targets.
3. Set Quality, Resolution, or Trim (optional): Under File Compression, keep the "Very High (Recommended)" Quality Preset or switch to Constant Quality (CRF), Constant Bitrate, or Specific file size; under Video resolution choose a Preset Resolution or Resolution Percentage; under Trim pick Time Range to keep only part of the clip.
4. Convert and Download: Click Convert. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark.

Frequently Asked Questions

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

It re-encodes. This tool has no stream-copy or remux mode, so every conversion decodes the AV1 stream and encodes it again into the MKV. MKV output defaults to the H.264 codec, which means the picture is re-encoded to H.264 — a different, less efficient codec — unless you change the Video Codec. Selecting AV1 keeps the output in the AV1 family, but it is still a fresh encode rather than a lossless copy of the original bitstream.

Why is my MKV silent after converting from AV1?

Because a raw .av1 file has no sound to begin with. The extension names a video-only AV1 elementary stream (OBU or IVF), and audio only exists once video has been muxed with a separate audio stream. The MKV output defaults its audio codec to AAC, but with no source audio there is nothing to encode, so the file stays silent. That is expected for a raw AV1 source. To add sound, mux a matching audio file into the MKV afterward.

Does MKV support AV1 natively, or do I have to use H.264?

Matroska supports AV1 natively — the specification assigns AV1 the codec ID V_AV1, and players such as VLC (3.0+) and MPV decode AV1-in-MKV directly. So you can keep the output in AV1 by selecting AV1 in the Video Codec dropdown. Keep in mind two things: the default codec for MKV output on this page is H.264, not AV1, and this tool re-encodes rather than stream-copies, so even an AV1-to-AV1 conversion runs through a fresh encode.

Will AV1 inside an MKV play on my TV or media player?

On the desktop, generally yes — VLC, MPV, Kodi, Plex, and Jellyfin play AV1-in-MKV. The catch is hardware: many older smart TVs and set-top boxes open MKV fine but lack an AV1 hardware decoder, so they show a black screen or fall back to choppy software decode. For those devices, re-run with the Video Codec set to H.264, or use the AV1 to MP4 converter for the most widely compatible container-plus-codec pairing.

Will the MKV be larger than my original AV1 file?

It depends on the codec you choose. If you leave the default H.264, the file typically grows — often 30-50% larger at matched visual quality, because H.264 is roughly a generation behind AV1 in efficiency. If you set the Video Codec to AV1, the output lands close to the source size. H.265 (HEVC) sits between the two. You can offset any increase by trimming dead footage or downscaling before converting.

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 that encoders and test pipelines emit before the video is muxed into MKV, MP4, or WebM. AV1 is a royalty-free video coding format from the Alliance for Open Media, with its bitstream reaching version 1.0.0 in June 2018. AVIF is a different thing: a still-image format that reuses the same AV1 coding, so it is not what this video converter produces or accepts.

In our testing, how much does re-encoding AV1 to an MKV change the file?

In our testing, a 10-second 1080p raw .av1 stream re-encoded to an H.264 MKV at Constant Quality (CRF) 18 looked indistinguishable from the source in side-by-side viewing, but the H.264 MKV came out noticeably larger than the AV1 input — the size-for-quality cost of moving to an older codec. Setting the Video Codec to AV1 instead produced an MKV close to the original size, though it is still a re-encode, not a byte-for-byte copy of the source stream.

How long do you keep my AV1 file after converting?

AV1 encoding and decoding are CPU-intensive, so the conversion runs on our servers rather than in your browser. Your file is uploaded over an encrypted (HTTPS) connection, processed, and then deleted automatically after a few hours — it is never shared, made public, or used for anything other than your conversion, and there is no sign-up and no watermark. Because the work is server-side, the practical limit on big files is upload size and connection speed, not your device's power, so multi-gigabyte 4K AV1 streams convert fine. To trim a long file before uploading, use the Video Cutter.