If a recipient cannot open a HEIC photo, prepare a compatible copy rather than renaming the extension. Apple documents exporting HEIF images as JPEG or PNG in Photos or Preview on a Mac. Some sharing methods may convert automatically; that is not guaranteed for every delivery.
Export one photo first
Suppose a club needs a picture for a simple membership form. Keep your original and export one copy with a clear name, such as membership-photo.jpg. Choose the format the form actually accepts. Open the exported copy yourself before sending it.
Check the whole image, not just its thumbnail. Is the orientation right? Is the intended crop present? Are small details still readable at the size the recipient needs? These checks are more useful than repeatedly attaching the same unreadable file.
Confirm what arrived
Ask the recipient to open the saved attachment in the application they intend to use. A preview inside a message and a file ready for an upload are different checkpoints. If a website has a size limit, inspect the exported file's size rather than guessing from the original.
Do not delete the HEIC original just because the JPEG works. The copy serves this exchange; it does not need to replace your photo library. Review location information separately if it matters for the picture you are sharing.