# Custom property fallback

The backup value in var(), used when the property isn't set.

## What is a **custom property fallback**?

A **fallback** is the second value in `var()`, used when the custom property isn't set.

```css
.alert { color: var(--alert-color, crimson); }   /* crimson unless --alert-color is set */
```

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

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/custom-property-fallback