Convert · runs on your device
Convert MTS to MP4 in your browser
AVCHD .mts files already contain H.264 video, so Video Mender copies the video stream straight into MP4 and only re-encodes the AC-3 audio to AAC — fast, and visually lossless.
Nothing is uploaded
Drop video files here
MTS / M2TS · TS
Plays on effectively every browser, phone, TV and editor when it holds H.264 and AAC.
The universal baseline. Hardware decoding exists on essentially every device sold since 2010.
Files smaller than the limit are left alone. Capping usually looks better than lowering the bitrate.
Lossless and near-instant when it applies. It cannot reduce file size, so turn it off if you need a smaller file.
MTS and M2TS are what AVCHD camcorders record: an MPEG transport stream using 192-byte timestamped packets instead of the usual 188. The video inside is H.264, often 1080i or 1080p, and the audio is normally AC-3 or uncompressed PCM.
That combination leads to the most interesting path in this whole converter. The video needs no re-encoding at all — MP4 carries H.264 natively — but AC-3 audio in an MP4 has poor compatibility, so the audio alone is re-encoded to AAC. Video Mender labels this "video copied, audio re-encoded", and it is both fast and visually lossless, because the picture is never decoded.
The practical payoff is that a 20-minute camcorder clip converts in well under a minute rather than the many minutes a full re-encode would take, and the picture is identical to what came off the camera.
What this actually does to your file
Rewrap or re-encode
Video always copies when the source is H.264. Audio copies only when it is already AAC; AC-3 and PCM are re-encoded because MP4 support for them is unreliable across players.
Quality
The picture is untouched — the H.264 stream is copied, not re-encoded. Only the audio is re-compressed, and at the default 192 kbps AAC that is not audible.
- AVCHD footage is frequently 1080i interlaced. Nothing here deinterlaces, so interlacing in the source persists.
- Camcorders split long recordings into multiple MTS files at the 2 GB or 4 GB boundary. Each is converted separately.
- Copy the files from the camera or its AVCHD folder structure first — this tool reads files, not camera filesystems.
How to use this page
- Copy the .mts or .m2ts files off the camera or SD card.
- Add them here and confirm the badge says video is copied.
- Leave audio set to AAC so the MP4 plays everywhere.
- Start, then download each MP4.
Where the result plays
Checked against the containers and codecs this page produces, stated conservatively.
| Target | Works | Detail |
|---|---|---|
| Video editors | Yes | MP4 imports everywhere. MTS import needs AVCHD support the editor may not have. |
| Phones and tablets | Yes | MP4 plays natively; MTS does not appear in a phone gallery. |
| Browsers | Yes | MP4 plays inline. MTS is not a web format at all. |
| Camcorder software | Partly | Manufacturer software prefers the original MTS with its AVCHD metadata. |
The formats involved
| Format | Read | Write | What it is |
|---|---|---|---|
| MTS / M2TS | Yes | No | AVCHD camcorder recordings — an MPEG transport stream with 192-byte timestamped packets instead of the usual 188. |
| TS | Yes | No | MPEG transport stream: a broadcast and HLS format built for streams that can be joined mid-flow, so it has no single global header. |
| MP4 | Yes | Yes | The MPEG-4 Part 14 container. It is a wrapper, not a codec — an MP4 usually holds H.264 or HEVC video with AAC audio. |
| MKV | Yes | Yes | Matroska. The most permissive common container: it will carry almost any codec, plus multiple audio tracks, chapters and subtitles. |
| MOV | Yes | Yes | Apple QuickTime. Structurally a close cousin of MP4, which is why MOV files can often be rewrapped to MP4 with no re-encode. |
Tested limits
Real ceilings measured on real devices, not a marketing claim of unlimited.
| Limit | Desktop | iPhone / iPad | Why |
|---|---|---|---|
| File size — rewrap | 1.3 GiB | 384 MiB | Rewrapping never decodes a frame, so it tolerates far larger files. |
| File size — re-encode | 1.0 GiB | 256 MiB | Decoding holds uncompressed frames in memory, which is the real constraint. |
| Clip length — re-encode | 4:00:00 | 30:00 | Beyond this, progress reporting and memory behaviour stop being dependable. |
| Resolution — re-encode | 4096 × 2160 | 1920 × 1080 | A 4K frame is about 12 MB decoded, before the encoder allocates anything. |
If something goes wrong
The MP4 has no audio in QuickTime.
The audio was probably copied as AC-3, which QuickTime does not handle in MP4. Set audio to AAC and convert again.
Conversion is much faster than I expected.
That is correct rather than suspicious: the video stream is being copied, not re-encoded. Only the audio passes through a codec.
My recording is split across several files.
AVCHD splits at a fixed size boundary. Convert each part, then join the MP4 files with a separate tool.
Your video never leaves this device
This is a structural property of the application, not a policy we ask you to take on trust. There is no upload endpoint, no API route and no server action anywhere in the codebase, so there is nowhere for a video to be sent even by mistake.
- Conversion runs in WebAssembly inside this browser tab. The engine is served from this domain and loaded only when you start a job.
- The Content-Security-Policy restricts network connections to this origin, so the page is not permitted to contact a third party at all.
- Nothing is stored. Close the tab and every queued file and finished output is gone — which is also why you should download results before you leave.
- There are no accounts and no AI. Anonymous page views are counted — which page, roughly what country, what kind of device — and nothing whatsoever about your files.
The repository contains a test that fails the build if any media byte is passed to fetch, XMLHttpRequest, sendBeacon or a WebSocket. See the privacy page for how that is verified.
Questions
What is the difference between MTS and M2TS?
Practically none. Both are AVCHD transport streams; the extension differs by camera manufacturer and by whether the file was copied from the disc structure. Both are handled identically here.
Does converting MTS to MP4 lose quality?
The picture does not change at all, because the H.264 video is copied rather than re-encoded. Only the audio track is re-compressed, which is inaudible at the default bitrate.
Why re-encode the audio but not the video?
MP4 carries H.264 natively, so the video copies cleanly. AC-3 audio is technically permitted in MP4 but many players ignore it, so AAC is the reliable choice.
Will 1080i footage be deinterlaced?
No. Deinterlacing is a separate decision with real quality trade-offs and is not part of this converter, so interlacing in the source remains.
Can I convert a card full of clips at once?
Yes. Because the video is copied, batches of camcorder footage go through quickly, and you can download them one at a time or as a ZIP.
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