# ID selector

Starts with # and selects the one element with that id.

## What is an **ID selector**?

An **ID selector** starts with `#` and picks the one element with that id. It is very specific, so it is hard to override later.

```css
#site-header { height: 64px; }
/* <header id="site-header"> */
```

Level: Novice · [More CSS terms at this level](https://www.ask-codey.com/glossary/subjects/css/novice)

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/id-selector