Sending a video to someone stops being simple the moment it refuses to attach. The message sits there red, the file is 240 MB, and the recipient is waiting. This compressor exists to take that number down while leaving you with something you would not be embarrassed to publish.
What it actually does
The tool takes the clip you hand it and re-encodes it at a lower bitrate. That is the whole mechanism, and understanding it tells you almost everything you need to know. A video is stored as a stream of compressed picture frames plus a separate audio stream. Lowering the bitrate means spending fewer bits per second describing those frames, so the file shrinks and the picture gets slightly softer. The motion stays smooth and the audio track stays attached.
How to use it
Drop a file onto the tool and it starts reading the duration and size. The quality control is the only dial you get, and it is deliberately simple, because a dozen codec settings would make the tool worse for most people. Nudge it, export, and check. The info line afterwards puts the original size beside the new one, which is the honest way to see what your choice actually bought.
Choosing how far to push it
The temptation is to drag the quality all the way down for the smallest possible number. Resist it if the video is going somewhere other than a private message. Very low bitrate on a clip with movement is where compression artefacts are most visible, and they show up as smearing around edges rather than as a general softness.
Static talking-head footage is unusually forgiving. So is a clip you have already exported once at a modest bitrate. Footage full of fast motion, water, confetti or a crowd is the hard case, and those clips will compress less for the same apparent quality.
Common companions
If the real problem is that the video is longer than it needs to be rather than too heavy, cutting the dead parts first usually beats compressing harder. Shaving an intro and a long outro often removes more bytes than any quality setting can, and it improves the video as a bonus. If the destination is somewhere that insists on a specific resolution, resize the frame before you compress, not after, so you are not encoding detail you are about to discard.
Everything runs locally in the browser, so a client footage file, a birthday recording, or anything else you would hesitate to upload to a converter stays on your device the entire time.
Resolution is a separate lever
One thing that regularly confuses people is that shrinking a file and shrinking the picture are different operations, and this tool only does the first. A 4K clip and a 1080p clip of the same scene look broadly similar on a phone, yet the 4K file can be several times larger. If wherever you are sending it has a resolution ceiling, resizing the frame is usually a far bigger saving than lowering the bitrate, and it costs you much less visible quality. Lowering the bitrate degrades the picture gently everywhere; lowering the resolution discards detail permanently. If you plan to do both, resize first and compress second, so you never spend effort encoding detail that has already been thrown away.