Where HEIF came from
HEIF is the MPEG container specification standardised in 2015; HEIC is Apple's particular flavour of it. Sony Alpha, Samsung Galaxy and Nikon Z-series bodies all offer HEIF capture, and those files carry a .heif extension rather than .heic. The compatibility situation is identical: efficient in-camera, unusable on the open web.
The technical picture
Compression: Lossy HEVC intra-frame. Transparency: Supported. Animation: Image sequences supported. Colour: Up to 10-bit per channel, HDR. Typical file size relative to WebP: comparable to WebP, often slightly smaller.
Where it opens
Apple platforms and newer Sony/Samsung/Nikon cameras; no browser renders it. This is usually the deciding factor when choosing between HEIF and WebP — WebP renders in every browser but is uneven in desktop software, while HEIF has a very different support profile.
Converting HEIF to WebP
Photographers shooting HEIF on Sony, Samsung or Nikon bodies hit the same wall iPhone users do — the files are compact but no browser will show them. WebP is the web-ready equivalent. Extras stored in the HEIF container — depth maps, image sequences, 10-bit HDR — do not carry over; you get the main still image.
Converting WebP to HEIF
Convert WebP to HEIF when the destination is a camera-adjacent or Apple workflow that expects HEIF specifically. Expect the HEIF output to be comparable to WebP, often slightly smaller — that difference is the price of getting a format the destination will actually accept.