# Video Compressor - Shrink MP4 Online Free Lower file size with CRF quality or a target bitrate and compare before/after sizes ### Input & Quality Video file MP4 / WebM / MOV CRF quality Target bitrate CRF (18–35, higher = smaller) _28_ Compress Clear Processed in your browser. Max ~100 MB; keep the tab open until the download is ready. ### Compressed Preview Compressed video appears here ## Compress a video for sharing This video compressor creates a smaller MP4 copy for email, chat, issue trackers, and web uploads. Choose a quality setting when the picture matters most, or a target bitrate when you need to work toward a size budget. Start with a moderate setting and inspect text, faces, and fast movement in the preview. A smaller file always involves a trade-off: strong compression can make fine details look soft or blocky. The selected video is processed in your browser rather than uploaded to a video-compression server. Keep the original master and share the compressed copy. ## How to compress an MP4 online Try a moderate setting first, compare the file sizes, and only increase compression if the preview remains usable. 1. **Upload a video** Select an MP4, WebM, or MOV file up to about 100 MB. Nothing is uploaded to a server. 2. **Choose CRF or bitrate** Use CRF for quality-based compression (higher CRF = smaller file), or enter a target video bitrate such as 1500k. 3. **Press Compress** The tool creates a smaller MP4 using your selected quality setting. Status messages show progress while the conversion runs. 4. **Compare sizes** The page shows original and compressed byte sizes so you can judge whether another pass is needed. 5. **Download** The smaller MP4 downloads automatically. Clear the form to compress another clip. ## Example: reduce a screen recording for email ### Before A product walkthrough is too large for the team’s email attachment limit. ### After Choose a moderate quality setting, download the smaller MP4, and check that the interface text remains readable at normal viewing size. Trim unnecessary setup footage before compressing when duration-not just bitrate-is making the video large. ## Common video compression uses ### 1. Email attachments Create a smaller copy for a strict attachment limit. ### 2. Bug reports Make a screen recording easier for teammates to download. ### 3. Course uploads Reduce a draft clip before uploading it to a learning platform. ### 4. Phone sharing Send a shorter-download version over a chat app. ### 5. Portfolio previews Prepare a lightweight review copy while retaining the master. ### 6. Internal demos Share a smaller draft without sending the original recording. ## Quality setting or target bitrate? Use one control according to the constraint you have. | Priority | Quality setting | Target bitrate | | --- | --- | --- | | Visual quality | Best starting point | Less direct control | | Predictable size budget | Approximate | Better starting point | | Simple sharing copy | Yes | Yes | No single value is ideal for every source; inspect the exported result before distributing it. ## Compression limits - Compression is lossy and cannot recover detail removed from a prior export. - The tool does not promise an exact file size in one pass. - Long, high-resolution clips need more time and browser memory. - Keep the original source if you need an archive-quality version. ## File handling The selected video is processed in your browser and is not uploaded to a video-compression server. Keep this tab open until the download is ready; refreshing stops the current job. Downloaded copies follow your browser’s normal download settings. ## Frequently Asked Questions ### What is CRF and which value should I pick? CRF means Constant Rate Factor. Lower numbers keep more detail and produce larger files; higher numbers discard more detail and shrink the file. Values around 23 look near the original for many clips, 28 is a solid default for sharing, and 32–35 aggressively reduce size for chat or email. Start at 28, check the preview, then raise CRF if you still need fewer megabytes. ### When should I use a target bitrate instead? Bitrate mode helps when a platform or email system imposes a hard size or bitrate ceiling. Enter something like 800k or 1500k for the video stream. The encoder aims at that average rate. CRF is usually better when you care about visual quality first; bitrate is better when you care about a predictable size budget. ### Will compression ruin the picture? Any lossy re-encode removes some information. At moderate CRF settings most phone and screen footage still looks fine for messaging and web playback. Extreme settings introduce blockiness in motion and soft text. Always watch the preview, especially on slides or UI recordings where text must stay readable. ### Why did my file get larger? If the source was already heavily compressed, or you chose a very low CRF, the new encode can match or exceed the original size. Raise CRF or set a lower bitrate, or trim the clip first so there is less footage to encode. ### Is audio compressed too? Yes. Audio is re-encoded to AAC at about 128 kbps by default, which is enough for speech and most music beds. The tool focuses on overall file size rather than audiophile masters. ### Are my videos uploaded? No. Compression runs in your browser; the selected video is not sent to a video-compression server. ### How is this different from trimming? Trimming shortens duration. Compression keeps the full length but spends fewer bits per frame. Many workflows trim first, then compress, which multiplies the savings. ### What output format do I get? The tool downloads an MP4 designed for broad browser and device playback. Review the result before replacing an important original. ### Can I compress to an exact kilobyte target? Not with a single guaranteed pass. Bitrate mode gets you close if you know the duration. For an exact KB ceiling, estimate bitrate from target size and length, compress, check the reported size, and adjust. ### Why is the first compress slow? The first compression can take longer while the page prepares its media-processing components. Later jobs are usually quicker; time also depends on duration, resolution, and your device. ## Prepare and reuse your video - [Video Trimmer](https://www.toolcomb.com/video-trimmer) - Remove unused footage before compression. - [Video Resize & Crop](https://www.toolcomb.com/video-resize-crop) - Change the frame dimensions. - [Video to GIF](https://www.toolcomb.com/video-to-gif) - Turn a short moment into a silent loop. - [Video to MP3](https://www.toolcomb.com/video-to-mp3) - Save only the audio track. ## Related Tools Discover more free tools that might help with your next task. [Add Music to Photo Still photo + soundtrack → MP4 video Use Tool](https://www.toolcomb.com/music-to-photo) [Remove Audio from Video Mute a video / strip the soundtrack Use Tool](https://www.toolcomb.com/remove-audio-from-video) [Add Music to Video Replace a video soundtrack with your music Use Tool](https://www.toolcomb.com/add-music-to-video) [Audio Trimmer Cut MP3/WAV clips by start and end time in the browser Use Tool](https://www.toolcomb.com/audio-trimmer) [Audio Joiner Merge multiple audio files into one track Use Tool](https://www.toolcomb.com/audio-joiner) [Audio Converter Convert between MP3, WAV, OGG, and M4A locally Use Tool](https://www.toolcomb.com/audio-converter) ### Related guides Read the how-to, then come back to this tool when you are ready to run it locally. - [How to Trim and Compress Video Without Uploading Cut screen recordings and shrink MP4 for Slack, LMS, and email caps using FFmpeg.wasm locally. CRF vs bitrate, ~100 MB limits, and resize when needed.](https://www.toolcomb.com/blog/how-to-trim-and-compress-video-without-uploading) - [Best Free Browser Audio and Video Tools (FFmpeg.wasm) Trim, join, compress, GIF, MP3, subtitles, and waveform exports without uploading media. How ToolComb's FFmpeg.wasm tools map to real chores - and where ~100 MB and first-load limits apply.](https://www.toolcomb.com/blog/best-free-browser-audio-and-video-tools) [View All Tools](https://www.toolcomb.com/tools)