Hi everyonr, I'm uploading a video to S3 using a presigned POST URL. In JavaScript, I manually build a multipart/form-data body (bucket, policy, credential, signature, key, and the file itself as separate parts) and send it with fetch/XMLHttpRequest.

This works fine on Android and Web, but fails on iOS with:

• XMLHttpRequest → onerror, readyState: 4, status: 0
• fetch() → TypeError: Load failed

I've tried both manual multipart construction and native FormData, and both fetch and XHR — same failure every time on iOS only.

Has anyone run into this or knows why iOS behaves differently here, or how to get a multipart POST upload to S3 working reliably on iOS?