Reviewed 2026-10-20 by the Spool editorial team · How we test
One converter, every common format
Drop any video and choose an output: MP4, MOV, MKV, WebM, AVI, WMV, FLV, M4V, 3GP, MPEG, TS, GIF, or MP3 for audio only. Inputs can be any of those plus MTS/M2TS camera files, OGV, VOB from DVDs and more. Everything runs on FFmpeg, the open-source engine whose libraries also power VLC, OBS and many professional editors.
Smart remux: why some conversions finish in seconds
A video file is a container (the extension) holding encoded streams (the codecs). If the streams in your file are allowed in the target container, we copy them instead of re-encoding. This is called remuxing. It's lossless and limited only by disk speed. If they aren't allowed, we encode, and the progress bar tells you which is happening.
| Target | Video copied if it is | Audio copied if it is |
|---|---|---|
| MP4 | H.264, HEVC, AV1 | AAC, ALAC, AC-3, E-AC-3 |
| MOV | H.264, HEVC, ProRes, Motion JPEG | AAC, MP3, ALAC, PCM, AC-3 |
| MKV | Anything | Anything |
| WebM | VP8, VP9, AV1 | Opus, Vorbis |
| TS | H.264, HEVC, MPEG-2 | AAC, MP3, AC-3, MP2 |
| M4V | H.264, HEVC | AAC, AC-3 |
| FLV | H.264 | AAC, MP3 |
Other targets (AVI, WMV, MPEG, 3GP, GIF) always encode, because they use their own legacy codecs. Remuxing only happens on the default Balanced setting with no resolution change. Choosing High or Smaller file, a resolution, or an audio bitrate means you want new encoding, so we do it.
What gets encoded with what
| Output | Video codec | Audio codec |
|---|---|---|
| MP4, MOV, MKV, M4V, FLV, TS | H.264 (High profile) | AAC |
| WebM | VP9 | Opus |
| AVI | MPEG-4 Part 2 (Xvid-compatible) | MP3 |
| WMV | WMV 8 | WMA |
| MPEG | MPEG-2 | MP2 |
| 3GP | H.264 (Baseline profile) | AAC 96 kbps stereo |
| GIF | 256-colour palette, two-pass | None |
The H.264 quality presets are High (CRF 20), Balanced (CRF 23) and Smaller file (CRF 28). For MP4 and MOV output we also move the index to the front of the file ("fast start"), so it begins playing immediately when streamed or previewed online.
Which format should you choose?
| You want to… | Choose |
|---|---|
| Play on any phone, TV or computer, or upload to social media | MP4 |
| Edit in Final Cut Pro or iMovie | MOV (or MP4) |
| Keep multiple audio/subtitle tracks or archive a recording | MKV |
| Embed on a website with a small file | WebM |
| Play on an old DVD player with a USB port | AVI |
| Insert into old PowerPoint versions | WMV |
| Feed DVD authoring software | MPEG |
| Send to a feature phone or keep tiny | 3GP |
| Loop a short clip in chats or email | GIF |
| Just the soundtrack | MP3 |
For the background on each format, see the format guide. Popular one-click pages: MOV to MP4, MKV to MP4, WebM to MP4, AVI to MP4, MP4 to GIF.
What's kept and what isn't
- One video track and the first audio track are converted. Extra audio tracks and subtitle tracks are left out.
- General metadata such as title and creation time is copied where the target supports it.
- Frame rate is kept, except for MPEG output, where non-standard rates are rounded to 30 or 60 fps for DVD compatibility.
- Resolution is kept unless you pick a maximum; vertical videos are scaled by their short side.
Limits
Convert and edit files on your device. The browser edition accepts up to 100 MB total, media up to 10 minutes and video up to 4K. Codec availability and device memory can limit individual jobs.