When you open a tool and choose a file, VideoDock uses the browser File API to reference bytes already on your disk. Nothing is transmitted; there is no upload request.
The file is decoded into a video element. Each tool draws frames to a Canvas, applies its transformation, and records the result with MediaRecorder — or reads samples directly for audio and frames.
The finished file is assembled in memory and offered as a download straight from the tab. Your footage never leaves the device.