Why build it this way
Every popular online GIF tool works the same way: you hand over your file, a server does the work, you download the result. That is a reasonable engineering choice and a bad deal for you. Your screen recording of an internal dashboard, the photos of your kid, the clip from a call — all of it sits on somebody else's disk, under a retention policy you did not read.
Browsers can now decode video, run shaders, and encode GIF and MP4 without help. Once that became true, the upload stopped being necessary, and a tool that still requires one is asking for trust it does not need. So we built the version that does not ask.