Most "Photos can't open it but other viewers can" cases come down to a missing Store extension, because Photos relies on Windows codecs while viewers like IrfanView or XnView ship their own. A quick way to work through it:
1. Check what the file really is. The extension can lie (e.g. a HEIC renamed to .jpg). In PowerShell:
Format-Hex .\photo.jpg | Select-Object -First 2
```- `FF D8 FF` = JPEG
- `89 50 4E 47` = PNG
- `ftypheic` / `ftypmif1` near the start = HEIC/HEIF
- `ftypavif` = AVIF
- `RIFF....WEBP` = WebP
**2. Install the matching extension from the Microsoft Store:**
- HEIC/HEIF: "HEIF Image Extensions" **and** "HEVC Video Extensions from Device Manufacturer" (free; the one without "Device Manufacturer" is paid)
- AVIF: "AV1 Video Extension"
- WebP: "Webp Image Extensions" (built into recent Windows 11 builds)
- Camera RAW: "Raw Image Extension"
Close Photos completely and reopen it after installing.
**3. File association:** Settings > Apps > Default apps > Photos, and check the extension is assigned to Photos.
**4. App problem:** Settings > Apps > Installed apps > Photos > Advanced options > Repair (then Reset if Repair doesn't help). Also check Microsoft Store > Library for pending updates.
**5. Integrity:** if the file opens elsewhere, re-save a copy from that viewer and try the copy in Photos. If the copy opens, the original uses an unusual encoding profile (common with some 16-bit or CMYK files) rather than being corrupt.