What this converter actually supports
Convertr uses the deployed FFmpeg toolchain for published audio and video routes. A container such as MP4, MOV, MKV, AVI, or WebM can hold different codecs, so the file extension alone does not guarantee that a particular player will accept the contents.
Use MP4 for phones, browsers, televisions, social uploads, and broad distribution; use MKV when flexible stream support matters more.
The public upload limit is 1 GB. Convertr does not reduce dimensions, duration, resolution, or output quality merely to manage worker load.