Video Compressor Guide
Reference for compressing short videos with ffmpeg.wasm in the browser, including formats, CRF, resolution, audio bitrate, mobile limits, and errors.
Quick answer
Choose a local video, select MP4 or WebM output, adjust CRF, max width, and audio bitrate, then start compression. The tool loads ffmpeg.wasm after processing begins and is intended for short practical clips rather than long professional editing jobs.
Supported input
Use browser-readable video files such as MP4 or WebM. Codec support depends on the browser and ffmpeg.wasm. If a file fails to load or decode, try a shorter clip, a different browser, or a desktop video editor.
Output controls
- Format: MP4 or WebM
- CRF: quality/file-size tradeoff; higher values usually make smaller files
- Max width: downscale wide videos for publishing contexts
- Audio bitrate: reduce speech or music track size when appropriate
Data handling and processing behavior
Processing is handled in the browser for this tool based on the current public implementation. Avoid entering sensitive media unless you have reviewed the implementation and your own data handling requirements.
Video compression can use significant CPU and memory. Mobile devices may struggle with larger clips.
Step-by-step use
- Check the source with Video Info Inspector
- Pick a target width that matches the publishing surface
- Start with a moderate CRF such as 28-30 for screen recordings
- Export a sample or short clip first when possible
- Review readability, motion, audio, and final size before using the file
Common errors
Processing fails after loading. The file may be too large, the browser may be out of memory, or the codec may not be supported.
Output is blurry. Lower CRF, keep a larger width, or trim instead of over-compressing.
Output is still large. Use Video Trimmer to remove unused time, or use Video Bitrate Calculator to plan a target size.
Limits
This guide is for everyday browser-side preparation. For long videos, batch jobs, production mastering, or exact codec control, use a dedicated desktop tool or command-line ffmpeg.
Next steps
- Video Info Inspector — inspect duration, dimensions, and bitrate before compression
- Video Bitrate Calculator — estimate target bitrate from duration and size
- Video Trimmer — remove unused sections before compression
- Video Format Converter — convert short clips between MP4 and WebM