A color profile (ICC profile) tells software exactly which real-world colors your image's numbers represent. The profile defines the color space / gamut.
The common ones
- sRGB — the standard for the web; every browser and device assumes it.
- Adobe RGB — wider gamut, used in pro photography and print.
- Display P3 — wide gamut on modern Apple screens.
The classic gotcha
Save a photo in Adobe RGB and upload it untagged, and browsers will read the numbers as sRGB — making it look dull and washed out. The fix: convert to sRGB before publishing to the web.
For the web, keep everything in sRGB. To learn how colors are stored, read color bit depth and RGB vs CMYK.