Video Compressor

What this tool does

Video Compressor re-encodes one or many videos to H.264 and AAC in an MP4 container, the most widely playable combination. You control the constant rate factor (CRF), maximum resolution, frame rate and audio bitrate, and the tool reports the size before and after for every file.

Modern phones record 4K at 50 Mbit/s or more, which is far beyond what you need for an email attachment, a chat message or a course upload. Many services cap uploads at 16, 25 or 100 MB, so a two-minute clip can be rejected outright.

This compressor uses the x264 encoder inside a WebAssembly build of FFmpeg. Instead of a fixed bitrate it uses CRF (constant rate factor), which keeps visual quality consistent and spends bits only where the picture needs them. On the x264 scale of 0 to 51, 23 is the default, 18 is close to visually lossless, and every 6 steps up roughly halves the file size. Lowering the resolution and frame rate cuts the size further. Everything runs locally, so private footage never leaves your device.

How to use Video Compressor

1. Drop one or more videos onto the upload area, or click to browse.
2. Pick a preset: Email / WhatsApp, Balanced or High quality.
3. Fine-tune Compression (CRF), Maximum resolution, Frame rate and Audio if needed.
4. Choose an Encoder speed: Very fast is a good default; Medium gives slightly smaller files but takes much longer.
5. Click Compress and follow the progress bar for each file; Cancel stops the current job.
6. Compare the sizes in Results and download files individually or as a ZIP.

Tips for better results

• Downscaling 4K or 1080p to 720p usually saves more than raising the CRF, with less visible damage on phone screens.
• Screen recordings with mostly static content compress extremely well; try CRF 30 or higher.
• Mono speech needs no more than 64 to 96 kbps AAC.
• If the result is larger than the original, the source was already efficiently compressed; raise the CRF or lower the resolution.

Common use cases

• Getting a clip under an email attachment limit of 20 to 25 MB.
• Reducing lecture or tutorial recordings before uploading them to a learning platform.
• Saving phone storage by shrinking old 4K home videos to 1080p.
• Preparing product videos for a website where page weight matters.

Common mistakes to avoid

• Setting CRF very high on footage with lots of motion, which produces blocky artefacts; lower the resolution instead.
• Compressing an already compressed file repeatedly; quality drops with each generation.
• Choosing Medium encoder speed on a phone: single-threaded WebAssembly encoding can take several times the clip length.