Video Compressor Guide
Reference for compressing short videos with ffmpeg.wasm in the browser, including quick presets, MP4/WebM output, CRF, resolution, audio bitrate, mobile limits, and errors.
Quick answer
Choose a local video, start from a quick preset for upload, chat/email, readable UI demos, or silent preview, then adjust MP4/WebM output, CRF, max width, and audio bitrate before compression. The tool loads ffmpeg.wasm after processing begins and is intended for short practical clips rather than long professional editing jobs.
What this tool does
The compressor re-encodes a local video with browser-side ffmpeg.wasm settings to reduce file size. It is designed for short publishing-prep clips where a quick local compression pass is enough: upload forms, chat attachments, email support clips, documentation demos, and web publishing previews.
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
- Quick presets: practical starting points for upload, chat/email, readable UI demos, and silent previews
- 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 the quick preset closest to your goal: upload, chat/email, readable UI demo, or silent preview
- Adjust target width and CRF if the clip has small text, fast motion, or a strict file-size limit
- Export a sample or short clip first when possible
- Review readability, motion, audio, and final size before using the file
Practical workflow
Compression should usually happen after inspection and trimming. Use Video Info Inspector to check duration and dimensions, Video Trimmer to remove unused time, and Video Bitrate Calculator when a platform has a target size. The Video Publishing Workflow separates short-video publishing from audio, subtitle, and GIF preparation.
Practical handoff note
For video compression handoff, copy source size, output size, CRF or quality setting, max width, audio setting, and visual review result together. Compression should be judged by readability and motion as well as file size. Keep the source file until the compressed output has been accepted.
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.
Text becomes unreadable. Use the readable UI demo preset, lower CRF, or keep a larger width. UI recordings often fail on text clarity before they fail on motion.
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 Publishing Workflow — decide whether to inspect, trim, compress, convert, extract a thumbnail, or make a GIF
- 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
- Video Thumbnail Extractor — export a readable cover frame after compression decisions