The fastest way to shrink a video is to re-encode it at a higher CRF, which typically cuts a file to 25–40% of its original size with no obvious quality change. If that is not enough, the next biggest lever is resolution, then length. Below is what each option actually costs you, a size reference chart, and a free video compressor that runs in your browser without uploading anything.
Why your video is so large
File size is roughly bitrate × duration. Bitrate is how much data each second of video is allowed to use, and it is set when the video is recorded or exported. Modern phones record at very high bitrates because storage is cheap and they would rather over-capture — a minute of 4K iPhone footage is around 350 MB.
That is why "it's only a minute long" and "it's 350 MB" are both true at once.
Typical video file sizes
| Resolution | Bitrate | 1 minute | 5 minutes |
|---|---|---|---|
| 4K (2160p) 60fps | ~50 Mbps | ~375 MB | ~1.9 GB |
| 4K (2160p) 30fps | ~45 Mbps | ~340 MB | ~1.7 GB |
| 1080p 60fps | ~12 Mbps | ~90 MB | ~450 MB |
| 1080p 30fps | ~8 Mbps | ~60 MB | ~300 MB |
| 720p 30fps | ~5 Mbps | ~38 MB | ~190 MB |
| 480p 30fps | ~2.5 Mbps | ~19 MB | ~94 MB |
Use this to sanity-check a target: if you need to email a 5-minute clip under 25 MB, no amount of clever compression gets you there at 1080p — you need to drop the resolution, the length, or both.
The five ways, ranked by quality cost
1. Re-encode at a higher CRF (best trade)
CRF is H.264's quality dial. Lower means better quality and a bigger file. Raising it re-compresses the video more aggressively while keeping the resolution intact, which is why it is almost always the right first move.
| Preset | CRF | Typical size vs original | Best for |
|---|---|---|---|
| High | 20 | 50–70% | Archiving, re-editing later |
| Balanced | 26 | 25–40% | Email, Slack, general sharing |
| Small | 32 | 10–20% | WhatsApp, slow connections |
Balanced is genuinely hard to distinguish from the original on a normal screen. Small is visibly softer in fast motion but still perfectly watchable.
2. Lower the resolution
Going from 4K to 1080p removes three quarters of the pixels and cuts size roughly proportionally. If the video will only ever be watched on a phone or in a chat window, 4K is invisible anyway — this is free size savings for most footage.
3. Trim the length
Size scales linearly with duration, so cutting a 3-minute clip to 45 seconds cuts the file by about 75%. A lossless trim copies the streams rather than re-encoding, so it costs no quality at all — often the cleanest win when the video has dead space at either end.
4. Remove the audio
Audio is usually 5–10% of the file. Not a big lever on its own, but free if the video does not need sound — remove the audio track and it is gone with no re-encode.
5. Lower the frame rate
Dropping 60fps to 30fps roughly halves the data. It looks fine for talking heads and screen recordings and noticeably choppier for sport or gaming.
Hitting a specific limit
| Target | Common limit | What usually works |
|---|---|---|
| Gmail attachment | 25 MB | Balanced preset, or 720p |
| Outlook attachment | 20 MB | Balanced + 720p |
| 16 MB | Small preset, trim first | |
| Discord (free) | 10 MB | Small preset + 480p |
| Slack | 1 GB | Balanced is plenty |
There is a dedicated guide for the most common case: compress a video for email.
What not to do
Don't zip it. Video is already compressed; a ZIP will save you a percent or two and add a step for whoever receives it.
Don't re-compress a compressed file repeatedly. Every re-encode throws away more detail permanently. If you need a smaller file, go back to the original and compress once at a higher CRF rather than compressing the compressed copy again.
Don't upload it to a random converter site if the content is personal or confidential. Most online compressors process on a server and retain the file for some period. The compressor here runs ffmpeg inside your browser, so the video never leaves your device.
Related tools
- Compress video — pick a preset, see before/after size
- Trim video — lossless cut, no re-encode
- Remove audio from video
- MP4 to GIF — when it should be a GIF instead