Convert · compress · batch — nothing uploaded
Fix the video formats that will not play
Video Mender converts and compresses video entirely inside your browser. Queue a folder of MKV, AVI, MOV or WMV files, get MP4 back, and watch real progress rather than a spinner — no upload, no account, and published limits rather than vague promises.
Nothing is uploaded
Drop video files here
MP4 · MOV · MKV · WebM · AVI · WMV · M4V · TS and more
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.
Platform presets — editable
These are dated observations, not permanent platform limits — each was last checked on 2026-08-01. Every one sets an ordinary target size you can edit afterwards.
Convert a format
14 conversions, each with its own honest answer about whether your file needs re-encoding at all.
- MKV → MP4MKV to MP4Rewrap is attempted whenever the MKV holds H.264, HEVC or MPEG-4 video with AAC or MP3 audio. VP8, VP9, Theora, FLAC and Vorbis have to be re-encoded because MP4 has no standard way to carry them. AC-3 is a special case: MP4 permits it but QuickTime and Safari play it silently, so the video is still copied while the audio alone becomes AAC.
- MOV → MP4MOV to MP4Rewrap runs whenever the MOV holds H.264, HEVC or MPEG-4 video with AAC or MP3 audio, which covers iPhone recordings and most QuickTime exports. ProRes, DV and Motion JPEG video are re-encoded to H.264 because MP4 has no standard way to carry them. PCM audio is converted to AAC while compatible video is still copied.
- MP4 → WebMMP4 to WebMThere is no rewrap path for MP4 to WebM in either direction. The codecs the two containers accept do not overlap at all, so the fast-copy badge never appears on this page.
- MP4 → MOVMP4 to MOVRewrap runs for H.264, HEVC and MPEG-4 video with AAC or MP3 audio, which covers virtually every MP4 in existence. MOV additionally accepts uncompressed PCM audio, so nothing in a normal MP4 blocks the copy.
- AVI → MP4AVI to MP4A minority of AVI files already contain H.264, and those can be rewrapped with no re-encode — the queue detects it and shows the fast badge. Xvid, DivX and Motion JPEG all require re-encoding, because MP4 has no reliable way to carry them.
- WMV → MP4WMV to MP4There is no rewrap path. WMV 9, WMV 8, VC-1 and Windows Media Audio are all decode-only in this build, and MP4 cannot carry them regardless, so the fast-copy badge never appears on this page.
- HEVC → MP4HEVC to MP4MP4 legally carries HEVC, so the fast rewrap path is available whenever you keep the codec. It disappears the moment you ask for H.264, because changing codec means decoding and encoding every frame.
- MP4 → AVIMP4 to AVINo rewrap path is offered. AVI predates modern per-frame timing and handles H.264 B-frames badly, so copying the stream across would produce a file that plays unreliably on exactly the old hardware this conversion exists to serve.
- M4V → MP4M4V to MP4Rewrap is the normal and expected path for every DRM-free M4V, since MP4 accepts exactly the codecs M4V uses. A re-encode is only needed if you also change resolution, frame rate or codec.
- TS → MP4TS to MP4Rewrap runs when the stream holds H.264 or HEVC with AAC audio. AC-3 is a special case: MP4 permits it but many players ignore it, so the picture is still copied while the audio alone becomes AAC — the row says "Video copied". MPEG-2 video forces a full re-encode.
- VOB → MP4VOB to MP4No rewrap path exists. MPEG-2 video and AC-3 audio are decode-only in this build and MP4 support for MPEG-2 is unreliable, so every VOB is re-encoded.
- MTS → MP4MTS to MP4Video 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.
- 3GP → MP43GP to MP4Video copies when the 3GP holds H.264 or MPEG-4, which covers most files. Audio always re-encodes when it is AMR, because MP4 players do not reliably support it.
- FLV → MP4FLV to MP4Rewrap runs when the FLV holds H.264 with AAC or MP3 audio. FLV1 and VP6 always re-encode, because MP4 cannot carry either.
Make a file smaller
Target a size in megabytes, a quality level or a bitrate. Never a promise of no quality loss, because that promise is not real.
- CompressVideo compressorSet a target size in megabytes or pick a quality level, queue as many files as you like, and Video Mender compresses them locally — no upload, no account, and no file size cap beyond what your own device can hold.
- CompressMOV compressorDrop your .mov files in, set a target size or quality, and Video Mender re-encodes them locally — MOV recordings usually shrink by 60–80% because cameras record at far higher bitrates than playback needs.
- CompressWebM compressorAdd your .webm files, choose a target size or quality, and Video Mender re-encodes them in the browser — staying in WebM with VP8, or writing MP4 if you need the file to play on Apple devices.
- CompressAVI compressorAVI files compress unusually well because the video inside is old and inefficient — re-encoding an Xvid or DivX AVI to H.264 typically halves the size with no visible quality loss.
- CompressMKV compressorAdd your .mkv files, set a target size or quality level, and Video Mender re-encodes them locally — keeping the MKV container by default, or writing MP4 if you need broader playback.
Why do it in the browser at all?
Because uploading video is the slow, expensive and risky part. A gigabyte-scale film rip takes a long time to upload before a converter has done anything at all, and once it has left your machine you are trusting a stranger with a copy. Doing the work locally removes the wait and the question at the same time.
The trade-off is honest and worth stating: your own device does the encoding. A rewrap — copying streams into a new container with no re-encoding — is close to instant even for enormous files. A real re-encode takes real time, and on a phone it takes noticeably longer. Video Mender tells you which one your file needs before you start, and never fakes a progress bar to hide the difference.
Tested limits
Published rather than hidden, and enforced by the same numbers the scheduler uses.
| 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. |