Compatibility is a device mismatch, not a format debate
You already know PNG is fine. The pain is practical: iMessage share to a Pixel, a work laptop without Store codecs, a Linux machine, a Mac that still needs a portable PNG for a client. This spoke is cross-device access. Open the URL where you are. No plugins. No HEVC purchase. Phone browsers work for a few stills. Desktop is kinder for albums. Fast-feeling iPhone exports are just the same decoder on Apple silicon — still local, still no upload. If the phone gets warm, that is decode, not a hidden network transfer. Check Settings → Cellular if you are encoding a huge still on LTE; Wi-Fi is kinder. Apple-sharing story lives on the iPhone spoke. No-signup story lives on the free spoke. Hub is the general tool. JPEG and PDF siblings exist when PNG is the wrong output. Linux users who refuse proprietary blobs can still finish here because the work is WebAssembly in the tab, not a .deb from a random PPA.