Why a converter does not have to upload your file

Most online converters take your file, put it on a machine you do not control, and email you a link. That is simple to build. It is also why people hesitate to drop a family video on a random site.

Batonbox keeps the common path in the browser: WebCodecs for MP4 and WebM, canvas for images, pdf-lib for documents. The file never leaves the tab. A badge on the page says so only when it is true.

Some containers still need FFmpeg on the server — AVI, WMV, FLV, HEVC. Those jobs go through a whitelist encoder, count against the same daily quota, and are deleted when the response is sent. We would rather show a smaller menu than pretend a browser can write WMV.