Transmute is a free, open-source, self-hosted file converter supporting 100+ formats including images, video, audio, documents, spreadsheets, subtitles, and fonts. It runs entirely locally with no file size limits and no third-party access to files. Deployable with a single Docker command, it includes built-in authentication with role-based access, an OpenAPI-documented REST API for automation, and seven UI themes. It positions itself as a privacy-first alternative to cloud conversion services like CloudConvert and Convertio, with the added advantage of a free API.