Video Compressor — Free, in Your Browser

Quality mode (CRF slider) is the right default — it gives consistent visual quality across the whole video. Target size mode is for the cases where you have a hard limit (a 25 MB email attachment, a 50 MB upload cap). Target size mode may produce inconsistent quality in complex scenes because the bitrate is fixed; quality mode lets ffmpeg spend more bits on hard scenes and fewer on simple ones.

For screen recordings, 26 is the sweet spot — visually lossless for the human eye at chat size, with a 30–50% size reduction vs the original. For camera footage, 23 is visually lossless. For drafts and 'good enough' copies, 28 is fine. Above 30, quality loss becomes visible on most content. Below 20, the file gets large fast with no visible improvement.

Compression is the right call for any of these: Email attachment limits. Gmail caps attachments at 25 MB. A 2-minute 1080p screen recording is often 80–150 MB. Compress to 20 MB and the recipient gets the video without a Google Drive round-trip. Chat apps with upload caps. Slack caps at 1 GB per file but renders slow above ~50 MB. Discord caps at 25 MB on the free tier. A 480p 8 MB MP4 plays inline in both. Mobile data. A 50 MB video on cellular is a real cost. A 8 MB compressed version is fine. Storage. Multiplied across a year of recordings, the savings are real. 50 recordings × 50 MB = 2.5 GB; same 50 recordings at 10 MB each = 500 MB.

We use ffmpeg.wasm 0.12 with libx264 (H.264) for video and AAC for audio. Single-threaded (`-preset ultrafast`) because the WASM build is single-threaded — multi-threaded encoding would require SharedArrayBuffer and COOP/COEP headers, which add complexity for marginal speedup in a browser tab. In quality mode: `ffmpeg -i input.mp4 -c:v libx264 -preset ultrafast -crf -c:a aac -b:a 96k -movflags +faststart output.mp4` In target size mode: we calculate `bitrate = (targetMB * 8192 - 96 * duration) / duration` and use `-b:v k -maxrate k -bufsize k`.

We do not upload your video to any server. Compression happens entirely in your browser via ffmpeg.wasm. Your video never leaves your device. The output file is a Blob URL pointing at in-memory data. The only network traffic is the initial 31 MB ffmpeg.wasm download (cached for the rest of the session).

At CRF 23, no — visually lossless for screen recordings and most camera footage. At CRF 26, the difference is visible only if you pixel-peep; on a phone or laptop screen at normal viewing distance, the original and the compressed file look identical. At CRF 30+, the difference becomes visible — blocky edges in gradients, soft text, ringing around high-contrast edges. The right range for 'good enough' drafts is 26–28.

Audio is re-encoded to AAC at 96 kbps. For voice recordings this is fine (voice compresses well). For music or video with rich audio, bump to 128 kbps. We default to 96 kbps to keep the file size low for the common case (screen recordings with voice).

For a 50 MB video on a modern laptop, expect 1–3 minutes. Compression is single-threaded in the browser (ffmpeg.wasm) — a 4-core CPU does not help. The conversion runs in a Web Worker so the page stays responsive.