Your iPhone photos, turned into JPGs that open anywhere. The conversion happens inside your own browser — the photo is never uploaded to us.
Several at once is fine — everything stays on your device
Your browser cannot open HEIC, and no website can change that without uploading your photos to someone's server. These two routes keep your photos on your own machine.
Every photo from then on is a JPEG. Photos you already took stay HEIC. While you are there, set Settings → Photos → Transfer to Mac or PC to Automatic — that converts HEIC to JPEG as it copies across.
Windows 10 and 11 both support this. Some editions also prompt for the paid HEVC Video Extensions — that one is only needed for video, not for photos.
Google Photos opens HEIC and can export a JPEG: open the photo, tap ⋮ → Export or share it to any app, which converts it on the way out. Samsung Gallery does the same.
We could, technically — it is a few lines of code. HEIC photos are compressed with HEVC, and HEVC is covered by patent pools whose licences explicitly cover decoders offered through cloud services. We would rather send you to a route that already works than run an unlicensed decoder and quietly pass that risk to you. Using the decoder already built into your Apple device sidesteps it entirely, which is why the tool above is limited the way it is.