Convert jp2 to heic
A browser can't do this one — here is what it can do.
Desktop app only
Nothing that runs in a tab can write heic from jp2. This pair is waiting on the desktop build, which hands the job to the real command-line tools.
Browse what does workAbout JP2
JPEG 2000
A wavelet-based image format standardized in 2000, with lossy and lossless modes. It never caught on in web browsers, but digital cinema, medical imaging and map archives use it. Convert from JP2 to get a file ordinary apps can open; convert to it when an archive or imaging system requires it.
About HEIC
HEIC (HEVC-coded HEIF image)
HEVC-compressed images in a HEIF container. iPhones have saved photos this way by default since iOS 11 in 2017, at much smaller sizes than JPG, but Windows and many websites cannot open them without extra codecs. Convert HEIC to JPG or PNG to open iPhone photos on Windows, upload them to sites that reject HEIC, or share them.