Compress any video without losing quality — MP4, MOV, AVI, WebM. Presets for WhatsApp, Instagram, Twitter.
Built & maintained by Pappu Venkata Subbi Reddy, founder of Clacify · Updated August 2026
Video Compressor re-encodes any video file to a smaller size using real H.264 compression via FFmpeg compiled to WebAssembly (FFmpeg.js 0.11, running single-threaded so it works without special server headers) — the same encoder professional video tools use, running entirely inside your browser tab. Pick a preset built for where you're sending the video — WhatsApp, Instagram, Twitter/X, or Email — or set your own quality (CRF) and maximum resolution, and the tool re-encodes the video with libx264 and re-encodes the audio track to AAC, then shows you the size before and after and lets you download the result. Because everything runs client-side, the video file never leaves your device.
Compression runs through FFmpeg.js 0.11 (loaded from a CDN on first use and cached by the browser), which compiles the real FFmpeg encoder to WebAssembly and runs it single-threaded — deliberately, so it works in any modern browser without requiring the cross-origin isolation headers that multi-threaded WASM needs. The video is scaled down to your chosen preset's resolution cap (only if it's larger — a smaller source video isn't upscaled) and re-encoded with libx264 at the preset's CRF (Constant Rate Factor) value, which controls quality-vs-size trade-off directly rather than targeting a fixed bitrate. Audio is always re-encoded to AAC at 128kbps, and the output is written with the +faststart flag, which moves file metadata to the front of the MP4 so it can start playing before the whole file downloads — useful for anything you'll upload to social media or embed on a page. The whole pipeline — decode, scale, encode, mux — happens in your browser's WebAssembly runtime, so no video data is ever sent to a server.
| Preset | CRF | Max resolution | Aimed at |
|---|---|---|---|
| 30 | 720p | Staying under WhatsApp's ~16 MB media limit | |
| 26 | 1080p | Higher quality for feed/reel uploads | |
| Twitter / X | 28 | 720p | Staying comfortably under X's upload limits |
| 34 | 480p | Smallest file size — for attaching to an email | |
| Custom | 15–40 (your choice) | 360p–2160p (your choice) | Full manual control |
Lower CRF = higher quality and larger file; higher CRF = smaller file and more visible compression artefacts. CRF 28 is FFmpeg's own commonly cited "visually near-lossless for most content" default, which is why most presets here cluster around it.
Constant Rate Factor sets a target visual quality rather than a target file size or bitrate — the encoder spends more bits on complex, motion-heavy scenes and fewer on static or simple ones, aiming to keep quality consistent throughout the video rather than hitting an exact output size. That's why two videos compressed at the same CRF can end up quite different in file size: a screen recording of a static slide deck will compress far smaller than a handheld action video at the same CRF, because the encoder needs less data to represent the parts that barely change.
FFmpeg's WebAssembly core (~10 MB) has to load before any compression can begin, which the tool shows as a distinct "Loading FFmpeg engine…" step before the actual compression progress bar starts moving. Once loaded, it stays available for the rest of your session, so compressing a second video is faster to start. Because encoding runs entirely on your device's CPU rather than dedicated hardware, large files (roughly 1 GB and up) can take a while and use significant memory — the tool's own guidance is to use a modern browser with enough RAM for anything sizeable.
WhatsApp has a maximum video share size of 16 MB (without compression). Upload your video to Clacify's Video Compressor, select the WhatsApp preset, and click Compress. The tool reduces the video to under 16 MB while maintaining the best possible quality. The compressed video downloads to your device — no server upload required.
Typical compression ratios: 1080p 60fps raw video → 70–85% file size reduction to a standard streaming quality MP4. A 200 MB video can typically be compressed to 30–60 MB at 720p quality. WhatsApp preset (max 16 MB): reduces most 2–5 minute videos to meet the limit. Compression quality depends on original codec, motion complexity, and your target settings.