Every converter page leads with formats. Use the limits instead
Open any online converter and the headline is a format count. CloudConvert's video converter lists 28 video formats, and its wider catalog runs to 212 formats across 11 categories; Canva's converter takes video in and sends MP4, WebM or GIF out. Both statements are true, and neither tells you whether your file will actually convert. That is decided one layer down, in the limits.
The limits, as the pages state them
CloudConvert's MKV to MP4 and MP4 to AVI pages state no file-size limit, and its flow is upload, set resolution, quality and file size, convert. Canva's video and MOV to MP4 converters cap files at 1 GB. Canva's AI file converter caps at 300 MB, takes one Illustrator file at a time, and requires an account before the conversion runs. CloudConvert asks for no account for a standard conversion. None of this is hidden; it is simply never the headline, which is why a 2 GB screen recording discovers it at minute nine of an upload.
The three limits that matter, in order
First, the size cap, checked against your largest real file, not your average one. Second, the batch rule: one file at a time is a different product from a queue when a project has forty clips. Third, the sign-in tax: an account is not a cost until it is a delay, a password reset, or a file sitting in a service you did not plan to join. Watermarks and export resolution on free tiers belong on the same checklist; this blog's format compatibility chart post tracks which editors impose them.
Pick the converter by your file, not by the list
Big archival files and one-off conversions favor the no-stated-cap, no-account route. Files already living inside a design workflow favor the converter attached to that workflow, cap and sign-in included. The formats were never the decision; they are the price of admission. The limits are the decision.