What does the compression slider do?

The slider maps to FFmpeg's CRF (Constant Rate Factor) setting. Light compression uses a low CRF (higher quality, larger file). Heavy compression uses a high CRF (lower quality, smaller file). Medium is the default and suits most use cases.

At what point does quality become noticeably worse?

For most content, you won't notice quality loss until Heavy (above CRF ~30). Fast motion, fine detail, and text are most sensitive to compression. If the compressed video looks blocky or blurry on playback, move the slider toward Light.

Can I make a video smaller without any quality loss?

Not through re-encoding — any re-encode is lossy by nature. However, you can get very close to lossless at the Light setting. If the source was originally encoded at a very high bitrate (e.g., from a camera), compressing at Light loses no perceptible quality while cutting the file in half.

Is my video uploaded to a server?

No. Compression uses FFmpeg.wasm — a WebAssembly build of FFmpeg running entirely in your browser tab. Your video files never leave your device.

Completely free — no account, no credit card, no watermark on output.

No upload · 100% free · Works in your browser

Smaller videos, free forever.

Reduce video file size right in your browser. Nothing is uploaded. Ever.

Why video file size matters

A 5-minute screen recording at 1080p from most screen recorders is 300–800 MB. A 1-minute iPhone video in 4K can be 400 MB. These files are too big for email, too slow to upload to Notion or Google Drive, and often rejected by messaging apps.

The reason most videos are so large is that they're encoded with a very high bitrate — far more data than the human eye can distinguish. Compression with H.264 at a moderate CRF value throws away the imperceptible data, keeping the video looking identical at a fraction of the file size.

How to compress video online

1
Drop your video
Drag MP4, MOV, MKV, WebM, or other video files onto the compressor, or click to browse. Up to 5 files at once.
2
Set compression level
Use the slider to choose between Light (preserve quality), Medium (balanced), or Heavy (smallest file). Medium works for most use cases.
3
Compression runs in your browser
FFmpeg.wasm re-encodes the video with a higher CRF value to reduce bitrate. No data leaves your device.
4
Download the compressed video
Save each video individually or download all as a ZIP. Before and after file sizes are shown so you know exactly how much was saved.

Compression levels explained

Light: Low CRF (~18–22). Near-lossless quality. Best for footage you'll edit further or archive. File size reduction is modest — typically 20–40% smaller than an unoptimised source.

Medium (default): CRF ~26–30. The sweet spot. Indistinguishable from the original for most viewers at normal viewing distances. Files typically 50–70% smaller than the original.

Heavy: CRF ~33–40. Maximum compression. Acceptable for messaging, previews, or content where small size is the priority over visual fidelity. Not recommended for archival.

Frequently asked questions

Why Compress

Email attachments, messaging apps, and social platforms all have file size limits. A 1-minute screen recording can be 200–500 MB straight from your screen recorder — way over Gmail's 25 MB attachment limit or WhatsApp's 100 MB limit. Compressing to 30–50 MB makes it shareable without cloud storage.

It depends on the source. Unoptimised screen recordings or videos shot at high bitrates often compress 50–80% with no visible quality change at Medium setting. Already-compressed videos (e.g., downloaded MP4s) will compress less — typically 20–40%.

Quality Settings

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