Without JavaScript the boxes below are disabled, and no name is looked up.
#2B35A0 or three numbers like 43, 53, 160. The four nearest names are shown, nearest first.Color Name Finder
The nearest CSS color name to a value — with the distance, because most colors do not have a name and the honest answer is how close you got.
Why it is the "closest" name
There are 148 named colors in CSS, and about sixteen and a half million values a screen can show. So almost every color you look up has no name, and the only honest answer is which name is nearest and how far away it is. This page always says both.
That is why the distance matters more than the name. A ΔE near zero means the name is the color; around 1 means a difference most eyes would not see; ten is a visible but related shade; past twenty-five the name is simply the closest label in the list, not a description.
How "nearest" is measured
Colors are converted to CIE Lab using the D65 white point, and compared with ΔE76 — the straight-line distance between the two points in that space. Lab is used instead of raw RGB because equal steps in Lab are much closer to equal steps as the eye sees them: two dark colors 30 apart in RGB may look identical, while two light ones 30 apart look obviously different.
ΔE76 is the simplest of the standard difference formulas, and it is not perfect — later formulas such as ΔE2000 model the eye better, particularly for saturated colors. This page uses ΔE76 because it is easy to explain and check, and the answer it gives is "which name is nearest", not a colorimetric verdict.
About the list
The names are the standard CSS color names — the ones every browser already understands, like rebeccapurple, gainsboro and papayawhip. They are a public standard, which is why this page can use them without licensing anyone's list, and their values were read from a browser rather than typed in by hand.
They are also historical and inconsistent. darkgray is lighter than gray, which surprises everybody the first time; several names have both gray and grey spellings; and the set has no system behind it. That is the standard's quirk, not a mistake here.
What it does not do
It does not name a color in any human sense — nobody agrees where teal ends and cyan begins — and it does not use a marketing or paint-manufacturer name list. For the same value in other notations, use the Color Converter; to see it at full-screen size, the Color Picker; and to build a set around it, the Palette Generator.
Everything is calculated in your browser from the value you type. Nothing is sent anywhere and nothing is kept.