# Video Compressor

> Shrink video file size with adjustable quality — locally, with no upload limit.

To compress a video, add the file and raise the quality number to make the file smaller. CRF 23 is visually lossless, 28 is a good balance for the web, and above 32 compression artefacts become visible. Downscaling the resolution saves considerably more than CRF alone.

**URL:** https://convertto.tech/t/video-compressor
**Category:** Audio & Video Tools (https://convertto.tech/c/media-tools)
**Privacy:** Runs entirely in the browser; no upload
**Cost:** Free, no sign-up
**Last updated:** 2026-08-01

## Key facts

- **Engine:** FFmpeg compiled to WebAssembly
- **First run:** Downloads ~30 MB of FFmpeg core, then cached
- **Upload:** None — the file never leaves your device
- **Privacy:** Runs entirely in your browser — nothing is uploaded
- **Cost:** Free, unlimited, no sign-up

## How to use

1. Select your video file — the file stays on your device and is never uploaded.
2. Set the quality.
3. Choose the resolution.
4. Choose the speed.
5. Press Run, then download the result when it is ready.

## FAQ

### What does CRF actually control?

Constant Rate Factor targets a consistent perceptual quality rather than a fixed bitrate. Every increase of about 6 roughly halves the file size. 18 is near-lossless, 23 is the x264 default, and 28 is a common web setting.

### Why is the first run slow?

The FFmpeg WebAssembly core is about 30 MB and downloads once per session. After that it stays in the browser cache, and subsequent conversions start immediately.

### Is my video uploaded anywhere?

No. FFmpeg runs inside your browser as WebAssembly, so the file is read from disk into memory and never sent to a server. That is also why there is no file size limit beyond your available RAM.

### Why is it slower than desktop FFmpeg?

WebAssembly runs single-threaded here and cannot use your GPU, so encoding is typically several times slower than a native build. For a short clip that is fine; for a feature-length film, use desktop FFmpeg.

## Related tools

- [Video Converter](https://convertto.tech/t/video-converter): Convert video between MP4, WebM and MKV entirely in your browser.
- [Compress PDF](https://convertto.tech/t/compress-pdf): Reduce PDF file size by re-rendering pages at a lower resolution and quality.
- [Remove Audio from Video](https://convertto.tech/t/mute-video): Strip the audio track from a video without re-encoding the picture.
- [Video Frame Extractor](https://convertto.tech/t/video-frame-extractor): Pull still frames out of a video as images — for thumbnails and contact sheets.
- [Video to MP3 Converter](https://convertto.tech/t/video-to-audio): Extract the audio track from a video and save it as MP3, WAV, AAC or OGG.
- [Video to GIF Converter](https://convertto.tech/t/video-to-gif): Turn a video clip into an animated GIF with control over frame rate and size.
- [Video Trimmer](https://convertto.tech/t/video-trimmer): Cut a clip out of a video by start and end time, without uploading it.
- [Audio Converter](https://convertto.tech/t/audio-converter): Convert audio between MP3, WAV, AAC, OGG and FLAC in your browser.