Video Compressor Online UniConverter allows you to compress video, reduce video file size online for free without losing quality. The compressed files can be saved to Dropbox or downloaded directly. How to compress video? Step 1. Click the Video Compressor extension icon and select Video Compressor. It will open an online video compressor tool. Step 2. Drag and drop or click the + icon to import video files you want to compress. Step 3. Choose an output format like MP4 from the Convert all files to > Video tab. Step 4. Hit the CONVERT button to start the video compression process. Step 5. Click the DOWNLOAD or Save to Dropbox button to get the compressed files.