Question 1

What is a CSS selector?

Accepted Answer

A CSS selector is the part of a CSS rule that defines which HTML elements the styles apply to. Examples include tag selectors (div), class selectors (.card), ID selectors (#header), attribute selectors ([type=text]) and pseudo-classes (:hover).

Question 2

How do I test a CSS selector?

Accepted Answer

Paste your HTML into the left input, type a CSS selector into the field at the top and the tester will instantly highlight every matching element, show the match count, compute the specificity score and list the matched HTML.

Question 3

What is CSS specificity?

Accepted Answer

Specificity is how browsers decide which CSS rule wins when several rules target the same element. It is expressed as (a, b, c) where a = ID count, b = class/attribute/pseudo-class count and c = element/pseudo-element count. Inline styles override everything except !important.

Question 4

What selectors are supported?

Accepted Answer

All modern CSS selectors work, including :is(), :where(), :not(), :has(), child combinators (>, +, ~), nth-child(), attribute selectors and pseudo-elements. The tool uses the browser native querySelectorAll engine.