Video Optimizer

What Video Optimizer does

Video Optimizer is the video tool for file size: it re-encodes a clip as an H.264 MP4 at the quality level you choose, usually to make it smaller for sharing or uploading. Colors, format options, and dimensions are handled by Video Color Changer, Video Converter, and Video Resizer.

It has a single control, Constant Rate Factor, and keeps the frame size and frame rate of the original. It also moves playback data to the start of the file so it can begin playing while still loading, and drops file-level metadata tags such as title and location.

How to use it

1. Select Choose File to load a video. Its name and size appear at the top, and the clip plays under Input Preview.
2. Set the Constant Rate Factor slider. The default of 30 aims for a clearly smaller file.
3. Select Render and wait for the progress bar to finish.
4. Compare Original size with Output size and watch the Output Preview for blur or blocky patches. If it looks too rough, lower the value and render again.
5. Select Download Video to save the copy ending in -optimized.mp4.

Formats and limits

• Input: any video file the picker allows, with MP4, MOV, WEBM, MKV, and AVI listed first. The FFmpeg engine inside the page has to be able to decode it.
• Output: MP4 with H.264 High profile video in the widely supported yuv420p pixel format, plus AAC audio at 128 kbps.
• Encoding uses the slow x264 preset, which spends extra time per frame to save space, so long or 4K clips can take a long time.
• Only one video is processed at a time, and the full file sits in memory while it is encoded.

Settings explained

Constant Rate Factor

From 10 to 45, default 30. Every rise of about 6 roughly halves the bitrate. Values from 18 to 23 keep most detail, 28 to 35 suit previews and chat apps, and above 40 the picture breaks up quickly.

Reset Values

Puts the slider back to 30 and clears the last render, ready for a fresh attempt.

Further reading

• When a file is too large for a browser tool - Compare compressed file size with decoded memory and choose a practical workflow for large images and videos.
• Make a video small enough to send - Choose between trimming, resizing, and compression, then check the downloaded video in its destination.

Privacy

Compression runs on your device through FFmpeg compiled to WebAssembly. The engine is fetched from the jsDelivr CDN, or from this website if the CDN cannot be reached, the first time you select Render; the video itself stays on your computer. Because file-level tags are removed, the optimized copy also carries less information about where and when it was made.

FAQ

Why is my optimized file bigger than the original?

The source was already compressed efficiently, or the CRF value is low. Raise Constant Rate Factor and render again.

Will the resolution change?

No. Width, height, and frame rate stay the same. Shrinking the frame with Video Resizer as well cuts the size further.

Why is rendering so slow?

The encoder runs on a single thread inside the browser and uses a thorough preset. Short clips finish quickly; long high-resolution recordings can take many minutes.

Can I save as WebM instead?

No, the output is always MP4. Video Converter can record WebM with VP9 or VP8 if your browser supports it.

Related tools

• Video Resizer - lower the resolution, which also cuts file size.
• Video Cutter - cut the clip shorter, which also shrinks it.
• Mute Video - drop the soundtrack to save a little more.
• Video Converter - save as WebM or pick another codec.
• GIF Optimizer - reduce the size of an animated GIF instead.