Reduce Video File Size

Video files are large because they contain an enormous amount of visual data. A single frame of 1080p video contains over 2 million pixels, each with color information. At 30 frames per second, that's over 60 million pixel values every second. Without compression, one minute of 1080p video would require approximately 10GB of storage. Modern codecs like H.264 reduce this dramatically through spatial and temporal compression, but cameras and screen recorders often use fast, less efficient encoding to keep up with real-time capture — leaving significant room for further compression.

Video content accounts for 82% of all internet traffic according to Cisco's annual report, making file size reduction one of the most impactful optimizations you can perform. Whether you're trying to fit a video into an email attachment, speed up a website, or free up storage on your phone, reducing video file size is almost always possible without meaningful quality loss.

There are three levers you can use to reduce video file size, and our tool gives you control over all of them:

1. Lower the quality (CRF). The quality slider adjusts the Constant Rate Factor. Lower quality means the encoder discards more visual detail, producing a smaller file. The default 70% quality (CRF 23) is widely considered the sweet spot — files are 50-70% smaller with differences that are invisible in normal viewing. Drop to 50% for aggressive compression when file size matters more than perfection.

2. Reduce the resolution. Downscaling from 4K to 1080p removes 75% of the pixels in every frame. Going from 1080p to 720p removes another 55%. This is the most effective single change you can make when you need dramatic size reduction. Most viewers on phones and tablets cannot distinguish 4K from 1080p content at normal viewing distances.

3. Choose the right codec. H.264 (MP4) is the standard codec with broad compatibility. VP9 (WebM) achieves approximately 20-30% smaller files at equivalent quality but takes longer to encode and has slightly less device support. For maximum compression, choose WebM; for maximum compatibility, choose MP4.

Different platforms have different file size limits. Here are the most common targets and recommended settings to hit them:

Email (25MB): Quality 50%, resolution 720p or 480p for videos over 1 minute. Most email providers including Gmail, Outlook, and Yahoo enforce a 25MB attachment limit.

WhatsApp (16MB): Quality 40-50%, resolution 480p. WhatsApp compresses videos further after receiving them, so there is little benefit to sending higher quality.

Discord (25MB free, 50MB Nitro): Quality 50-60%, resolution 720p for short clips. Discord does not re-encode your video, so the quality you send is the quality others see.

Slack (1GB but practical limit ~100MB): Quality 65-75%, resolution 1080p. Slack preserves your original file, so higher quality is worthwhile.

The estimated output size displayed before compression helps you dial in the exact settings needed for your target platform.

Every byte of your video stays on your device. Our tool uses FFmpeg compiled to WebAssembly, which runs the entire compression pipeline locally in your browser. There are no uploads, no server processing, and no temporary file storage. This makes our tool safe for compressing personal videos, business content, and any footage you would not want a third party to handle.

You can verify this by monitoring the Network tab in your browser's developer tools during compression. Apart from the initial page load and the FFmpeg WebAssembly binary download, you will see zero network activity. Once the page and FFmpeg core are loaded, you can even disconnect from the internet and continue compressing videos offline.