Check the destination's file limit before changing a video's quality. You might only need a shorter excerpt or smaller dimensions. Keep the original, save a delivery copy, and try the change that solves the obvious problem first.
Start with the useful duration
If the video has a long lead-in, a pause after the action, or another clip that doesn't belong in the message, trim it first. Open Video Cutter, choose the video, and set the Start and End handles on the timeline. Play selection previews the range you'll keep. Watch the first and last moments, not only the middle.
Fast (copy) keeps the existing streams, but its cut boundaries can land on nearby keyframes. Exact (re-encode) produces H.264 video with AAC audio in MP4 and follows the selected boundaries more closely. A quick rough excerpt and a carefully timed demo may need different modes.
Save the trimmed copy and check it before moving on. A smaller file that loses the setup for a joke or the last step in a tutorial isn't a successful edit.
Match the frame size to the destination
A clip meant for a small message preview may not need the original frame dimensions. Video Resizer lets you enter a Width (px) and keeps the proportions while Lock Aspect Ratio is on. Select Render Preview after the change, then check the output dimensions and watch the rendered clip.
The resizer writes H.264 MP4 with AAC audio. Its video quality setting is fixed at CRF 23, so this page is mostly for changing dimensions. Width and height must be at least 16 pixels and are rounded up to even numbers when rendering. Keep the ratio locked unless you want the picture stretched to the two dimensions you enter.
Choose a size that leaves the important details readable. If the clip has small interface text, compare that text at the size the recipient will see. Shrinking everything until it's unreadable defeats the point of sending a screen recording in the first place.
Try a quality change on its own
Video Optimizer works on compression and keeps the frame dimensions and frame rate. Choose File, set Constant Rate Factor, and select Render. The output is an H.264 MP4 with AAC audio at 128 kbps. The download name ends in -optimized.mp4.
The quality control runs from 10 to 45 and starts at 30. A higher CRF tells the encoder to accept more quality loss, and a lower value tells it to keep more detail. CRF is a quality target, not an exact file size. The FFmpeg codec documentation describes the encoder's controls. You'll still need to check how your clip turns out.
Compare Original size with Output size, then watch the Output Preview. Pay attention to fast motion and the parts of the picture that carry your message. If it looks too rough, lower CRF and render again. If it's still too large, try a modest increase or go back to the duration and dimensions. The optimizer doesn't promise every output will be smaller than its input.
Avoid unnecessary passes
The cutter, resizer, and optimizer are separate tools. You don't need to use all three for every clip. Start with the change that solves the obvious problem, save the result, and check whether it already meets the destination's requirements. Every re-encode is one more conversion to check.
When comparing several optimizer settings, load the same source each time instead of optimizing the last optimized copy again. Jot down the settings and output size if that helps you choose between attempts. A good intermediate file gives you something to go back to if the next change goes too far.
Check the file you'll actually send
Download the result and open that file in the receiving app or upload form. Confirm the duration, picture, sound, and reported file size. The optimizer removes file-level metadata and moves MP4 playback data to the beginning of the file, but that doesn't replace a final compatibility check.
Processing runs on your device through FFmpeg in the browser. The page downloads the engine code, but the video stays local. Long or high-resolution recordings can take a lot of time and memory, so start with a short, representative clip when choosing your settings.
Fix captions before the final export
If the clip needs captions, check their timing before burning them into the delivery copy. The subtitle timing walkthrough includes a clip with two visible markers and an intentionally late subtitle file. If an export stalls or uses too much memory, the browser processing guide explains what to check next.