Shrink a video's file size by re-encoding it at a lower bitrate - processed entirely in your own browser, so the file never leaves your device. The video engine (~30MB) downloads once the first time you use any Video Tool, then stays cached.
Re-encodes using H.264 at a higher CRF (constant rate factor) than the original - a higher CRF means more compression and a smaller file, at some cost to visual quality. Output is always .mp4 regardless of the input format.