Compress a Video to a Specific MB Size
Most video tools ask for quality settings and leave you guessing the final file size. This compressor starts from the size you actually need, such as 20MB, 25MB, 50MB, or a custom MB value. It estimates the video and audio bitrate from the duration, keeps a small safety margin below the target, then creates a smaller file you can preview before downloading. If the first output is still too large, the tool retries with a lower bitrate instead of treating an over-limit file as a success.
Private Browser Video Compression
The selected video is processed locally in your browser with FFmpeg WebAssembly. It is not uploaded to this site, stored on our server, or sent through a third-party video API. The engine files are downloaded on first use, but your chosen video remains on the device. This makes the workflow useful for family clips, private messages, support recordings, and files you do not want to hand to an online converter. Refreshing or closing the page clears the working session, so preview the result and download it before leaving.
Supported Input and Output Formats
The tool accepts common video files such as MP4, MOV, WebM, MKV, AVI, M4V, MPEG, and MPG. It can export MP4 for broad compatibility, WebM for modern web use, MOV for QuickTime workflows, MKV as a flexible modern container, or AVI for older software. If an upload page is strict, MP4 is usually the safest choice because phones, forms, and messaging apps commonly accept it. The container is only one part of the result; bitrate, audio, duration, and resolution decide whether the file can stay below 20MB.
How Video Length Changes a 20MB Result
Twenty megabytes gives a short clip much more bitrate per second than a long recording. A one-minute video can often keep a useful 720p picture, while a fifteen-minute video must spread the same file budget across fifteen times as many seconds. In that situation, forcing 720p may produce heavy blocking or miss the target, so automatic resolution may recommend 360p or 240p. The recommendation is based on duration and available bitrate, not a fixed rule. You can force a higher resolution, but the warning explains the likely quality tradeoff before processing begins.
Why the Result May Be Below 20MB
The goal is to produce a file that an under-20MB upload limit accepts, not to pad the download to exactly 20.00MB. Video encoders cannot predict every frame with byte-level precision, so the tool reserves a small safety margin and may return a result slightly below the limit. If the first pass is still too large, it retries with a lower bitrate instead of showing an over-limit file as a success. A much smaller result usually means the source was easy to encode or a later retry had to be more conservative.
Use a Computer and Select CPU Cores
Compressing a long video to a strict target is demanding work. The page detects the logical CPU cores reported by the browser and enables multi-core FFmpeg when the required isolation is available. Browser WebAssembly can deadlock at the high thread counts used by native desktop encoders, so this tool deliberately caps encoding at four cores. Dual-core devices use two, and devices with four or more logical cores default to four. For large files, 4K footage, or videos near the 1GB input limit, use a desktop or laptop, close heavy tabs, and keep the device awake.
