WhatColorIsThisHex is an online color reference and lookup tool that helps users identify the names associated with hexadecimal color codes. Visitors can enter a color in six-digit or three-digit hex format, or provide an RGB value, to find an exact name when available or the closest named match. Each color has a dedicated page, and users can browse a collection of more than 24,000 named colors.

The site explains how color naming and comparison work, including the use of perceptual difference measurements and why RGB values alone may not reflect how colors look to people. Its names are drawn from five open sources, including CSS Color Level 4, the X11 color list, Wikidata, the xkcd Color Survey, and a community-maintained list. Beyond its lookup tool, WhatColorIsThisHex offers color browsing, a glossary, palettes, a contrast checker, format converters, and references to CSS color keywords. The service is designed for people who need to identify, compare, explore, or work with colors for digital projects.