How to compress a video in three steps
- Choose your file. Drag a video onto the box above or tap “Choose video”. It opens instantly because nothing is uploaded.
- Pick a setting. Use Target size when a platform has a hard limit (for example 20 MB for Discord or 25 MB for Gmail), or Quality when you just want a smaller file that still looks good.
- Compress and download. Watch the progress bar, compare the before and after size, and save the new MP4.
Why compress videos in the browser?
Most online compressors ask you to upload your file to their servers, wait in a queue, and then download it again. That is slow for large files and risky for personal footage. This tool uses ffmpeg — the open-source engine behind many professional video apps — compiled to WebAssembly, so all the work happens on your own computer or phone. Your video stays private, you are not limited by your upload speed, and there is no server-side queue to wait in.
The compression engine is only downloaded when you press the Compress button, so the page itself stays light and fast. After the first use, your browser usually caches the engine, so the next video starts quicker.
Which setting should I use?
Target size is best for sharing limits. The tool divides your target by the video length to find a bitrate, keeps a small safety margin for the audio track and container, and encodes once. Because the encoder cannot predict every frame perfectly, the result can land slightly above or below the number you entered, which is why we recommend aiming about 5–10% under a hard limit.
Quality mode uses a constant quality factor instead of a fixed size: High looks nearly identical to the original, Medium is a good default for social media and messaging, and Low produces the smallest file for previews and drafts. Quality mode is the better choice when you do not have a specific limit, because the encoder can spend more bits on complex scenes and fewer on static ones.
Resolution has the biggest effect on file size. A 4K phone clip downscaled to 1080p is often several times smaller with little visible difference on a phone screen, and 720p is plenty for chat apps. The tool never upscales: if your video is already smaller than the chosen resolution, it keeps the original size.
What actually makes a video file big?
A video file is mostly the video stream, and its size is roughly bitrate × duration. Modern phones record at high bitrates so the footage survives editing — a minute of 4K video can easily take hundreds of megabytes. Four things decide how far you can shrink it:
- Resolution: fewer pixels need fewer bits. Going from 1080p to 720p removes more than half of the pixels.
- Frame rate: 60 fps footage contains twice as many frames as 30 fps.
- Motion and detail: a static screen recording compresses far better than sports, confetti, rain or grass in the wind.
- Codec: this tool outputs H.264, the most compatible codec. Some phones record in HEVC (H.265), which is already efficient, so savings from re-encoding those files may be smaller unless you also lower the resolution.
Common sharing limits at a glance
Limits change from time to time, so always trust the message the app shows you. At the time of writing:
- Discord: 20 MB per file on a free account (raised from 10 MB in August 2026). Discord preset.
- Gmail: 25 MB of attachments per email. Email preset.
- WhatsApp: about 100 MB at 720p for videos sent as media on a fast connection. WhatsApp preset.
- Fixed targets: many forms and portals ask for files under 5 MB or 10 MB.
Tips for the best results
- Trim unnecessary seconds before compressing — a shorter clip gets more bitrate per second at the same file size.
- Lower the resolution before lowering the quality. A clean 720p video looks better than a blocky 1080p one.
- If you need an exact limit, aim slightly below it (for example 18–19 MB for a 20 MB limit).
- Keep your original file. Every re-encode loses a little detail, so always compress from the best copy you have.
Troubleshooting
The engine will not load. Use a recent version of Chrome, Edge, Firefox or Safari, and make sure your network does not block cdn.jsdelivr.net, where the engine is downloaded from. The tab crashes on a big file. Close other tabs, or lower the resolution — the browser holds the whole video in memory. The result is bigger than the original. That can happen with files that were already heavily compressed; choose a lower resolution or the Low quality level. For more control without quality loss, see compressing without losing quality.