Base64 to File

The type comes from the file header (magic bytes), not from the MIME in the data URL or the filename — renaming a PNG to .pdf is common, and saving by the declared type gives a file that will not open.

The ZIP header is also used by docx, xlsx, jar and apk, so those all come out as .zip.

Decoding happens in the browser and handles a few MB fine; tens of MB will visibly stall because it runs on the main thread.