Questions about HEIC and WebP
Why does WordPress refuse my iPhone photos?
WordPress does not accept HEIC uploads, because the servers it runs on usually cannot process the format. You get an error saying the file type is not permitted, with no hint about what to do — converting first is the fix.
How do I stop my iPhone making HEIC files?
Settings → Camera → Formats → Most Compatible. From then on the camera writes JPG. You lose a little storage efficiency and gain the ability to use your photos anywhere without a conversion step.
Which browser should I use for this page?
Safari, on a Mac or an iPhone. Apple built HEIC, so Apple's browser reads it natively. Chrome and Firefox have never shipped a decoder and show a decoding error instead.
Are my images really not uploaded?
Correct. The conversion uses your browser's own image engine, so the file is read from your disk into the tab and never sent over the network. Open your browser's network panel and convert something — no request is made.
How does the target size work?
The converter encodes your image, checks the result against your target, and adjusts quality until it fits. If quality alone cannot get there, it reduces the dimensions in steps rather than destroying the picture. You always see what happened.
Is there a limit on how many files I can convert?
None from us — your computer does the work, not our server. The practical ceiling is around 40 megapixels per image, where browsers stop being reliable.