Most "online converters" quietly upload your photos to a server. Mine decodes HEIC entirely in the browser (libheif-js + web workers) — nothing leaves your device. The upside: privacy as a real USP, zero server cost, instant conversion. The pain: a ~3MB library to code-split carefully, and brutal compatibility testing across iOS versions whose HEIC encoding keeps shifting. I still think it was the right call. Would you trade some edge-case robustness for a "we literally can't see your files" promise?