HEIC, AVIF and JPEG XL
The newest formats are the smallest — and some of them need a free extension from Microsoft for Windows to read them. Here is which, and why.
HEIC (iPhone photos)
Windows reads and writes HEIC itself, and Cobalt Photo uses it. For that, Windows needs Microsoft's free HEIF Image Extensions from the Microsoft Store — and, to decode the photo inside, the HEVC Video Extensions, which many PCs have from their maker.
- Without them, the viewer says so in the middle of the window: IMG_0412.heic is a HEIC picture: Windows reads it with the free HEIF Image Extensions from the Microsoft Store.
- HEIC is offered as a format to save to only when Windows can write it; otherwise its tile in Convert says what to install.
AVIF
Windows reads AVIF with its free AV1 Video Extension, already there on most Windows 11 PCs and in the Microsoft Store for the rest; Cobalt Photo opens AVIF through it. Saving AVIF needs nothing: Cobalt Photo writes it by itself.
JPEG XL
Cobalt Photo reads and writes JPEG XL by itself, on any Windows. Windows' own apps and Explorer's thumbnails show it only with the JPEG XL Image Extension from the Store, on Windows 11 24H2 and later — so a JPEG XL you send may not open everywhere yet.
WebP
Read and written by Cobalt Photo itself, animated WebP included; nothing to install.
Which to choose
For photos to keep: JPG opens everywhere; AVIF and JPEG XL take a half to two thirds of the space for the same look. For the web, WebP and AVIF. For sending to anyone at all, JPG — Formats and quality.