# Check if a string is a hexadecimal number

Test for one or more hexadecimal digits.

Canonical: https://1loc.dev/validator/check-if-a-string-is-a-hexadecimal-number/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function isHexadecimal(text) { return /^[0-9a-f]+$/i.test(text); }
```

## Input

```json
"ff00"
```

## Expected output

```json
true
```

## Edge case

Input:
```json
"0xff"
```
Output:
```json
false
```

## Limits

- A 0x prefix fails, as the edge case shows; strip it first.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/check-if-a-string-is-a-hexadecimal-number.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Keeps the regular-expression variant. Original MDX retained as inert source evidence.