Video Compressor
Compress videos to a target file size or custom quality in your browser. Re-encode offline without uploading footage to external servers or losing privacy.
MP4, WebM, MOV, MKV, AVI, FLV, 3GP · up to 1 GB
Tips
- The 30 MB encoding engine downloads once to your cache and works offline on future visits.
- Setting a target file size automatically calculates the optimal video bitrate for your clip duration.
- Downscaling resolution from 1080p to 720p delivers significant size savings without heavy compression artifacts.
How to use it
- 1 Select or drag your video file into the compression workspace.
- 2 Choose a target file size in megabytes or specify a custom CRF value and resolution.
- 3 Start the compression process and wait while your browser encodes the frames.
- 4 Save the compressed video file directly to your device.
What you should know
Uncompressed or high-bitrate video files quickly exceed upload limits on messaging platforms, email services, and e-commerce product listings. Video compression applies lossy encoding algorithms like H.264 to reduce file sizes by eliminating redundant spatial and temporal data between frames. Adjusting the Constant Rate Factor controls visual fidelity across scenes: a lower CRF value retains crisp details and dynamic range at the cost of a larger file, while a higher CRF discards subtle high-frequency details to shrink size. Balancing resolution, frame rate, and bitrate lets you achieve bandwidth-friendly clips that play smoothly across modern browsers and operating systems.
This tool re-encodes video entirely inside your browser tab using WebAssembly, ensuring your media files never leave your device. You can target a specific megabyte limit or pick a custom CRF value, with optional resolution downscaling to accelerate throughput. Re-encoding strips proprietary container metadata and recalculates audio tracks to fit your constraints. Because the engine runs single-threaded within the client environment, processing lengthy 4K footage may take several times the actual video duration. For optimal performance, trim unnecessary footage before compressing and keep the browser tab active until the exported file is ready.
Measured output sizes
Test clip: a 10-second, 1280×720 H.264 MP4 without an audio track (4.8 MB, animated film footage). Run on the live tool in Chrome 154 on a desktop PC. The first run includes starting the video engine.
| Output format | Quality | File size | Change | Time to encode |
|---|---|---|---|---|
| MP4 (H.264) | High (18) | 5.8 MB | +21% | 25 s |
| MP4 (H.264) | Balanced (23) | 2.3 MB | −52% | 20 s |
| MP4 (H.264) | Small (28) | 990 KB | −80% | 16 s |
| MP4 (H.264) | Smallest (32) | 512 KB | −90% | 16 s |
| WebM (VP8) | Balanced (23) | 1.2 MB | −75% | 10 s |
| WebM (VP8) | Small (28) | 1.2 MB | −75% | 10 s |
- High (18) made this clip larger than the source. That setting is for keeping quality when you change format, not for saving space.
- Each step down roughly halved the file: 2.3 MB at Balanced, 990 KB at Small, 512 KB at Smallest.
- WebM gave the same 1.2 MB at both quality levels. Its encoder is held to about 1 Mbit/s here, so on a short clip the quality chips change little; use MP4 when you need a specific size.
- Encoding a 10-second 720p clip took 16 to 25 seconds as MP4 and about 10 seconds as WebM, so expect a few minutes of waiting per minute of 720p video.
Frequently asked questions
Why does compressing video take longer than uploading to a server?
The compression engine executes WebAssembly in a single thread within your browser tab. Without multi-threaded server hardware, rendering complex video codecs can take several times the actual duration of the video.
What is CRF and which value should I select?
Constant Rate Factor (CRF) balances compression against visual quality. Lower values like 18 to 23 maintain crisp quality at larger file sizes, whereas values between 28 and 32 yield smaller files with visible compression.
Are my video clips uploaded or stored on any server?
No, all media processing happens locally in your browser memory. Your files are never transmitted across the network, ensuring complete privacy.
Guides
Articles and format references related to this tool.
- Free Video to GIF Converter: MP4, MOV & WebM to GIF 10 September 2026
- Free GIF to MP4 Converter: Turn Animated GIFs into Video 21 September 2026
- How to Convert Video Files for Any Device or Platform 9 September 2026
- What is an MP4 file? A container for H.264, H.265 or AV1 video with AAC audio
- What is a WebM file? A container for VP8/VP9/AV1 video with Vorbis or Opus audio
Related tools
- Video Merger Combine multiple video clips into a single file in your browser. Reorder tracks, match frame rates automatically, and merge footage without server uploads.
- Video Resizer Change video dimensions to 1080p, 720p, 480p, or custom pixel values directly in your browser. Lock aspect ratio to prevent stretching without uploading data.
- Video Cutter Trim video clips by selecting start and end timestamps. Choose instant stream copy or frame-accurate re-encoding with full privacy right inside your browser.
- AVI to MP4 Converter Convert legacy AVI videos into universal MP4 files right in your browser. Re-encode video using H.264 compression without uploading files to any server.
- FLV to MP4 Converter Convert legacy Flash FLV video files to modern MP4 format. Adjust video quality and resolution locally in your browser without uploading files to any server.
- MP4 to MOV Converter Convert MP4 videos to QuickTime MOV format directly in your browser. Adjust resolution and encoding quality while keeping your private files on your device.