compressvid.ioShrink multi-track MKV files to an exact size in MB. Output is a compatible MP4 — no watermark, nothing to install.
Quality mode targets CRF and does not guarantee an exact MB size. Switch to target size or bitrate for a hard limit.
Only use this for very old devices or playback issues (reduces compression ratio).
MKV (Matroska) is a flexible container: multiple audio tracks, subtitles, chapters and modern codecs all in one file. That flexibility is why screen rips and multi-language exports end up huge — and why some email clients, chat apps and smart TVs refuse to play them. Compressing MKV to a smaller MP4 keeps the main picture and sound while dropping the weight and the compatibility problems.
These caps apply to the file you attach — MKV or MP4. Aim a little under the limit so container overhead never pushes you over.
| Destination | Upload limit | Compress to |
|---|---|---|
| Gmail attachment | 25 MB | 24 MB |
| Outlook / work email | Often 20–25 MB | 19 MB to be safe |
| Discord (free) | 20 MB | 19 MB |
| Discord Nitro Basic | 50 MB | 48 MB |
| Cloud drives & share links | Large files OK, links expire | Smaller = faster send |
| Forms, LMS & job portals | Usually 10–100 MB | 5% under the stated limit |
Limits checked October 2026. Discord raised its free upload limit from 10 MB to 20 MB in August 2026 — older “8 MB” guides are outdated. Limits checked October 2026. Full breakdown: Discord file size limit.
No FFmpeg commands — set a target size and download. Keep the story in the picture; leave multi-track baggage behind.
Drop a screen capture, archive encode or multi-track MKV into the compressor above. MP4, MOV, AVI and WebM work too.
Type the size you need in MB — 24 for Gmail, 19 for Discord — or pick a percentage preset. The tool derives a bitrate from duration so the result lands near your target.
Output is MP4 with H.264 + AAC by default — the main video and audio stream, ready for email, chat or the browser. No watermark.
File size ≈ bitrate × duration. Use this as a planning table before you compress.
| Video length | Target size | Rough total bitrate |
|---|---|---|
| 15 seconds | 19 MB | ~10 Mbps — sharp 1080p is easy |
| 30 seconds | 19 MB | ~5 Mbps — clean 1080p |
| 60 seconds | 24 MB (Gmail) | ~3.2 Mbps — good 1080p / 720p |
| 2 minutes | 19 MB | ~1.3 Mbps — 720p recommended |
| 5 minutes | 19 MB | ~0.5 Mbps — 480p or cut a highlight |
| 60 seconds | 50% smaller | Half the original — usually looks fine |
If quality falls apart, drop resolution before starving the bitrate further. Multi-hour MKVs almost always need a highlight cut rather than a brutal squeeze.
MP4 is what most inboxes, chat apps and web players understand. When you compress this MKV, the tool keeps the primary video and audio track and writes a standard MP4 — the right default when someone just needs to watch the clip.
Multiple commentary or language tracks can dominate the file size. Sending one clear mix is usually what the recipient wants anyway.
Soft subs inside MKV do not always map into a share-ready MP4. If burned-in captions matter, add them before the final export.
That combo previews in more apps than HEVC or Opus-in-MKV. Choose H.265 in Advanced only when you control playback.
Answers for Matroska files that will not send or play.
Compress MKV to a smaller MP4 at the size you need — free to start, no watermark, nothing to install.