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.
Lossless and near-instant when it applies. It cannot reduce file size, so turn it off if you need a smaller file.
Platform presets — editable
These are dated observations, not permanent platform limits — all were last checked on 2026-08-01. Every one sets an ordinary target size you can edit afterwards.
Convert a format
Thirteen 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 a…
- MP4 → WebMMP4 to WebMThere is no rewrap path for MP4 to WebM in either direction. The codecs the two containe…
- MP4 → MOVMP4 to MOVRewrap runs for H.264, HEVC and MPEG-4 video with AAC or MP3 audio, which covers virtual…
- AVI → MP4AVI to MP4A minority of AVI files already contain H.264, and those can be rewrapped with no re-enc…
- WMV → MP4WMV to MP4There is no rewrap path. WMV 9, WMV 8, VC-1 and Windows Media Audio are all decode-only …
- HEVC → MP4HEVC to MP4MP4 legally carries HEVC, so the fast rewrap path is available whenever you keep the cod…
- MP4 → AVIMP4 to AVINo rewrap path is offered. AVI predates modern per-frame timing and handles H.264 B-fram…
- M4V → MP4M4V to MP4Rewrap is the normal and expected path for every DRM-free M4V, since MP4 accepts exactly…
- TS → MP4TS to MP4Rewrap runs when the stream holds H.264 or HEVC with AAC or AC-3 audio. MPEG-2 video and…
- VOB → MP4VOB to MP4No rewrap path exists. MPEG-2 video and AC-3 audio are decode-only in this build and MP4…
- MTS → MP4MTS to MP4Video always copies when the source is H.264. Audio copies only when it is already AAC; …
- 3GP → MP43GP to MP4Video copies when the 3GP holds H.264 or MPEG-4, which covers most files. Audio always r…
- FLV → MP4FLV to MP4Rewrap runs when the FLV holds H.264 with AAC or MP3 audio. FLV1 and VP6 always re-encod…
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…
- CompressMOV compressorDrop your .mov files in, set a target size or quality, and Video Mender re-encodes them loca…
- CompressWebM compressorAdd your .webm files, choose a target size or quality, and Video Mender re-encodes them in t…
- CompressAVI compressorAVI files compress unusually well because the video inside is old and inefficient — re-encod…
- CompressMKV compressorAdd your .mkv files, set a target size or quality level, and Video Mender re-encodes them lo…
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. |