OBS MKV to MP4: Remux It, Don't Re-Encode It

That is the whole fix for most people. The rest of this page is for the cases where it is not: why OBS picks MKV in the first place, what changed with Hybrid MP4, and what to do when a remuxed file still gets rejected by your editor.

Why does OBS record to MKV at all?

Because a recording can end badly, and MP4 handles that worse than almost any other format.

A regular MP4 keeps its index, the part that tells a player where every frame lives, in a block written at the very end of the recording. Until that block exists the file is a pile of compressed data with no map. OBS's own settings warning says it without softening: recordings saved to MP4 or MOV "will be unrecoverable if the file cannot be finalized", and it names blue screens and power losses as the usual causes. A full disk does the same thing. So does a game that takes the whole machine down with it.

MKV does not work that way. It is written so that everything recorded up to the moment of failure stays readable. The OBS knowledge base's standard recording output guide puts it as a recommendation: MKV "will not corrupt the whole file if there is no graceful stoppage of recording." For years the standard advice was exactly this: record in MKV, remux to MP4 afterwards.

What changed with Hybrid MP4

OBS 30.2 added a third option, Hybrid MP4. While the recording runs, the file is written in fragments, so a crash leaves everything up to the last fragment intact. When you stop recording cleanly, OBS writes a full index at the end and patches the start of the file so ordinary MP4 software sees a normal MP4. The developer who built it calls that step a "soft remux" in the OBS write-up on how Hybrid MP4 works. It avoids the old problems with plain fragmented MP4, which many editors and players handle poorly and which some players cannot seek through at all.

With OBS Studio 32.0, released in September 2025, Hybrid MP4 and Hybrid MOV came out of beta and became the default output format for new profiles. The key word is new. If your profile was set up before that, it keeps whatever format it had, which is why so many people on current versions still end up with a folder full of MKVs. Check Settings > Output > Recording > Recording Format to see which one yours uses.

What does Remux Recordings actually do?

Remuxing changes the box, not the contents. A video file has two separate layers: the container (MKV, MP4, MOV) that organises the data, and the codecs (H.264, HEVC, AV1, AAC) that actually compress the picture and sound. If that distinction is new, video container vs codec walks through it properly. OBS's remux reads each compressed packet from the MKV and writes it into an MP4 unchanged. Nothing is decoded and nothing is compressed a second time, so the output is bit-for-bit the same video, just in a different wrapper.

Step by step:

1. Open OBS. You do not need to stop anything else you are doing, but let the recording you want to convert finish first.
2. Choose File > Remux Recordings.
3. Click the empty cell under OBS Recording and browse to your file, or drag the file (or a whole folder of them) into the window.
4. OBS fills in the Target File automatically, same name, .mp4 extension, same folder.
5. Press Remux. A message confirms when it is done.

The window also accepts .mp4 and .mov inputs. In that case OBS writes a new file with .remuxed.mp4 (or .remuxed.mov) on the end rather than overwriting the original, which is useful for the crash case further down.

One behaviour catches people out: the Remux button stays greyed out until a file is actually in the queue. An empty window has one blank row for you to click into, and that blank row does not count.

How do you make OBS remux automatically?

Open Settings > Advanced, find the Recording group, and tick Automatically remux to mp4. From then on, every time you press Stop Recording, OBS runs the same remux in the background and leaves an MP4 next to the MKV. The status bar tells you when it has finished.

There is a useful twist in how this interacts with the format setting. If your Recording Format is set to plain MP4 or MOV, the checkbox label changes to "Automatically remux to mp4 (record as mkv)". That is not a typo. With the box ticked, OBS quietly records to MKV anyway and only produces the MP4 at the end, so you get MKV's crash safety and an MP4 to edit. It is the cleanest setup if you are on an older profile and do not want to switch to Hybrid MP4.

Two things to know before you rely on it:

• The MKV stays. Auto remux does not delete the original. On long sessions that means two copies of every recording until you clean up.
• A crash skips the step. If OBS never gets to a clean stop, there is nothing to trigger the remux. The MKV survives; you remux it by hand.

Which route fits your recording? A decision tree

Start with the state of the recording, then where it is going.

Your situation	Where it's going	What to do
Clean stop, MKV, H.264 video	Your editor	Remux in OBS. Done
Clean stop, MKV	Upload site or a colleague	Remux in OBS. If the recording used HEVC or AV1, re-encode to H.264 instead
Clean stop, you record often	Anywhere	Tick "Automatically remux to mp4", or switch new recordings to Hybrid MP4
OBS or PC crashed, MKV	Anywhere	Remux the MKV. If OBS warns the file "may be incomplete", check the end of the result
OBS or PC crashed, Hybrid or fragmented MP4	Editor or player	Run it through Remux Recordings to get a normal .remuxed.mp4
OBS or PC crashed, plain MP4	Anywhere	Likely unrecoverable. Switch formats for next time
Remuxed MP4 still rejected	Editor	Re-encode to H.264 with AAC audio (next section)
Several audio tracks you need separately	Multitrack editor	Remux. It keeps every track
Several audio tracks, sharing a finished file	Viewer or upload	Mix down or pick one track first, then send

The format names, menu paths and the Hybrid MP4 default above were checked against OBS's own documentation and release notes in September 2026. OBS changes these settings between versions, so if a menu looks different on yours, the release notes for your version are the place to look.

When does a remuxed file still fail in your editor?

Remuxing only fixes a container problem. If the editor's complaint is really about the codec, a new wrapper changes nothing. These are the usual causes, in rough order of how often they come up.

The video is HEVC or AV1. OBS can record with H.265 (HEVC) or AV1 encoders if your graphics card supports them, and they make smaller files at the same quality. The catch is on the playback side: an editor or laptop without the matching decoder will refuse the file, show a black frame, or play audio only. Remuxing to MP4 keeps HEVC as HEVC. The H.264 vs H.265 post goes into where HEVC quietly fails. If you control the settings, switching the recording encoder to H.264 avoids this for future sessions.

The audio is PCM, FLAC or Opus. OBS can write these, and MKV carries them happily. MP4 support for them is patchier. OBS's own Hybrid MP4 notes flag PCM in MP4 as "a relatively recent addition to the standard" that not every application reads. If your remuxed file has video and silent audio, this is the likely reason. Switching the recording's audio encoder to AAC fixes it at the source; a re-encode fixes the file you already have.

The recording never finished writing. When you remux a crashed MKV, OBS may report "Recording remuxed, but the file may be incomplete". The part before the crash is usually fine. The last second or two can be damaged, and some editors choke on that tail. Trim it off, or re-encode, which rebuilds the whole file cleanly.

It is just very large. Long gameplay recordings at high bitrates run into tens of gigabytes. The editor is not rejecting the format; it is struggling with the size. That is a separate problem with its own fixes, covered in reducing screen recording file size.

When is a full re-encode the better choice?

A re-encode decodes every frame and compresses it again. It takes real processing time and always costs a small generation of quality, so it should be the answer only when remuxing cannot be. That means:

• The codec inside will not play where the file is going (HEVC or AV1 to an older machine, a phone, or an editor without support).
• The audio format is one MP4 players do not handle.
• You want the file smaller as well as compatible, and are willing to trade a little quality for that.
• A crashed recording remuxes but still trips up your editor.

For those cases, VidClip's MP4 converter re-encodes to H.264 video at CRF 21 with AAC audio, the combination that plays on almost everything, and moves the index to the front of the file so it starts playing before it fully loads. It runs in your browser: the recording is read into the page's memory and processed on your own CPU, with no upload. To be plain about what it is and is not, it always re-encodes, it never remuxes. For a straight MKV to MP4 on a file your editor already accepts, OBS's remux is the better tool, and it is already on your machine.

A few limits worth knowing before you try it on an OBS recording:

• Size. The free tier takes files up to 200 MB and adds a small watermark in the corner of video exports. Pro removes both, and at that point the real ceiling is how much memory your browser can use. A multi-gigabyte recording is a better job for desktop software.
• One audio track out. The converter produces a single audio track, so a multitrack OBS recording comes out with one of its tracks, not all of them. If you need them separate, remux in OBS instead.
• Speed. Re-encoding in a browser is slower than a native encoder with hardware acceleration. For a short clip that you need to send in a format that plays anywhere, it is quick enough. For a two-hour stream, it is not the right tool.

If you want the reasoning behind the same remux-or-convert choice for iPhone footage, converting MOV to MP4 applies the same test to a different container.

Remux in OBS first. If your editor still rejects the file, convert it to H.264 MP4 here.

FAQ

Does remuxing MKV to MP4 lose quality?

No. Remuxing copies the compressed video and audio packets into a new container without decoding or re-encoding them. The picture and sound in the MP4 are identical to the MKV. Quality loss only happens when a file is re-encoded, which is a different operation.

Why is the OBS remux option greyed out?

In the Remux Recordings window, the Remux button stays disabled until at least one file is in the queue. Click the empty cell under "OBS Recording" to browse for a file, or drag a file or folder into the window, and the button becomes active. If the "Automatically remux to mp4" checkbox is the thing that looks off, check that you are in Settings > Advanced and looking at the Recording group.

Can I record straight to MP4 safely?

Plain MP4, no: if OBS cannot finish writing the file because of a crash, a power cut or a full disk, OBS itself warns the recording will be unrecoverable. Hybrid MP4, available since OBS 30.2 and the default for new profiles since 32.0, is designed for exactly this and stays recoverable up to the point of failure. The other safe route is to leave the format on MP4 and tick "Automatically remux to mp4", which makes OBS record to MKV and convert at the end.

What happens to multiple audio tracks when converting?

OBS can record up to six audio tracks, and its remux copies every one of them into the MP4. Whether you can use them depends on the software that opens the file: OBS's own guide notes that most video players only play one track at a time, while editors with multitrack support let you handle each separately. A re-encode is different. Most simple converters, VidClip's included, output a single audio track, so remux in OBS if you need the tracks kept apart.