A 10-minute screen recording can easily be 2 GB straight out of a capture tool. The same recording, properly compressed, might be 150–300 MB — visually indistinguishable on any screen. The gap is not magic: it's the difference between unoptimised output and H.264 with a sensible quality setting.
"Without losing quality" is a slight oversimplification. What you're actually doing is reducing quality imperceptibly — staying within the threshold where the human visual system can't detect the difference. Done right, the result looks identical on any screen short of a broadcast monitor.
What actually controls video file size
A video's file size is determined by its bitrate — the amount of data stored per second of footage. Unoptimised video tools often use constant high bitrates to guarantee quality. H.264 encoding with a CRF (Constant Rate Factor) setting instead allocates bits where they're actually needed: more for complex motion, fewer for static scenes.
Choosing the right quality preset
| Preset | CRF value | Best for | Typical size reduction |
|---|---|---|---|
| High | 18 | Archiving, print work, professional delivery | 30–50% |
| Medium | 28 | Sharing, uploading, general use | 50–70% |
| Low | 35 | Rough previews, fastest email attachment | 70–85% |
CRF 28 (Medium) is the right choice for almost everything. At this setting, the visual quality difference from the original is imperceptible at normal viewing distances on a standard monitor. CRF 18 is for work that will be displayed large or reviewed frame-by-frame.
What you can't compress away
File size after compression depends heavily on content. Talking-head videos with a static background compress extremely well — the encoder barely needs to store anything between frames. Fast-action sports footage, explosions, or rapid scene cuts give the encoder much less to work with and compress less efficiently. A 50% size reduction is realistic for most content; 30% is more typical for high-motion video.
How to compress a video in your browser
- 1Go to tools.zenwebx.com/video-compressor.
- 2Drop your MP4, MOV, AVI, or MKV file (up to 1 GB).
- 3Select Medium quality for most uses, or High if the output will be used professionally.
- 4Click Compress Video. A progress bar shows encoding status.
- 5Download the compressed MP4.
Processing runs in your browser via FFmpeg.wasm. No file is sent to a server. Expect 1–4 minutes for a 200 MB video, depending on your device.
Compress your video now
Three quality presets, up to 1 GB input, runs entirely in your browser. No upload.
Open Video Compressor