Video Compressor

How to Use

1. Click the area above to select a file, or drag and drop a file onto the page
2. Adjust parameters in the settings area
3. Click the process button and download the result when ready

Frequently Asked Questions

How It Works

The Video Compressor uses FFmpeg WebAssembly with the libx264 (H.264) or libvpx-vp9 encoders to reduce file size through lossy compression. The tool manipulates key encoding parameters: CRF (Constant Rate Factor), bitrate, resolution, and frame rate.

At its core, the compression engine performs inter-frame prediction — analyzing motion between consecutive frames and storing only the differences (P-frames and B-frames) rather than complete images (I-frames). The quality slider directly controls the CRF value: lower CRF means higher quality and larger files, while higher CRF increases compression at the cost of visual fidelity.

The tool also supports two-pass encoding for optimal bitrate distribution. Pass one analyzes the entire video to determine bit allocation per scene, and pass two applies the optimized bitrate. Resolution downscaling and frame rate reduction provide additional compression leverage, as pixel count and temporal data directly impact file size.

Tips & Best Practices

• Quality slider sweet spot: 70-85% provides the best balance between size reduction and visual quality for most content.
• Resolution matters most: Reducing from 1080p to 720p cuts file size by ~56% with minimal visible quality loss on most screens.
• Frame rate reduction: Dropping from 30fps to 24fps saves ~20% with negligible quality impact for non-action content.
• Content-aware compression: Talking-head videos compress much better than fast-action content at the same quality setting.
• Preview first: Process a 5-second sample to find the optimal settings before committing to the full video.
• Target file size: If you need a specific file size (e.g., under 25MB for email), calculate the target bitrate: bitrate = (target size in bits) / duration in seconds.

Use Cases

Email senders compressing video attachments to stay under 25MB attachment limits. Website managers reducing hero video file sizes to improve page load speed and Core Web Vitals scores.

Mobile app developers optimizing video assets for app store size limits. Teachers compressing recorded lectures for upload to LMS platforms with storage caps. Marketing teams preparing video ads that meet social media platform file size requirements. Backup archivists compressing family video collections to save storage space while maintaining watchable quality.

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