Hexadecimal Number Regex Pattern
Validates hexadecimal numbers with an optional 0x prefix. Use it for numeric hex literals; CSS color hex codes need a separate #RGB/#RRGGBB pattern.
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Pattern Breakdown
Code Examples
JavaScript
const regex = /^(0x)?[0-9a-fA-F]+$/; const test = "0xFF00FF"; console.log(regex.test(test)); // true // Extract matches const matches = test.match(regex); console.log(matches);
Python
import re pattern = r'^(0x)?[0-9a-fA-F]+$' test = "0xFF00FF" match = re.search(pattern, test) print(match) # Found!
Go
package main
import (
"fmt"
"regexp"
)
func main() {
re := regexp.MustCompile(`^(0x)?[0-9a-fA-F]+$`)
fmt.Println(re.MatchString("0xFF00FF")) // true
}Common Use Cases
Match Examples
| Input | Result |
|---|---|
| 0xFF00FF | Match |
| 0xGG | No Match |
Hexadecimal regex variants for 0x, CSS colors, bytes, and fixed length
The base pattern validates a numeric hex literal such as 0xFF00FF or FF00FF. Tighten the pattern when you need CSS colors, byte pairs, fixed-width IDs, or case-insensitive 0x/0X prefixes.
| Variant | Pattern | Use it when |
|---|---|---|
| Optional 0x or 0X prefix | ^(?:0[xX])?[0-9a-fA-F]+$ | Use for code literals, memory addresses, and config values where both 0x and 0X should be accepted. |
| CSS hex color | ^#?(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6}|[0-9a-fA-F]{8})$ | Use for #RGB, #RRGGBB, and #RRGGBBAA color inputs. Keep this separate from general hexadecimal numbers. |
| Exactly 8 hex characters | ^[0-9a-fA-F]{8}$ | Use for fixed-width checksums, compact IDs, ARGB colors, or packed 32-bit values. |
| Hex byte sequence | ^(?:[0-9a-fA-F]{2})(?:[\s:-]?[0-9a-fA-F]{2})*$ | Use for byte strings such as FF 00 A4, FF:00:A4, or FF-00-A4. |
Edge cases to test
0xFF00FFMatchMatches the base pattern because the 0x prefix is optional.
0XFF00FFNo match in base patternUse the 0[xX] variant if uppercase X should be valid.
#FF00FFNo match in base patternUse the CSS hex color variant for # prefixes.
0xNo matchAt least one hex digit is required after the optional prefix.
0xGGNo matchG is not a hexadecimal digit.
About the Hexadecimal Number Regex
Validates hexadecimal numbers with an optional 0x prefix. Use it for numeric hex literals; CSS color hex codes need a separate #RGB/#RRGGBB pattern.
Regular expressions (regex) are powerful pattern matching tools used across virtually all programming languages. The hexadecimal number pattern is classified as <strong>beginner</strong> difficulty in the <strong>numbers</strong> category. It works in all major programming languages.
When using this regex, always consider edge cases and test thoroughly with real-world data. Use the interactive tester above to validate the pattern against your specific inputs before deploying to production.
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Frequently Asked Questions
What is the Hexadecimal Number regex pattern?
Validates hexadecimal numbers with an optional 0x prefix. Use it for numeric hex literals; CSS color hex codes need a separate #RGB/#RRGGBB pattern.
How do I use the Hexadecimal Number regex?
Use the pattern /^(0x)?[0-9a-fA-F]+$/ in your code. In JavaScript: new RegExp('^(0x)?[0-9a-fA-F]+$', ''). Test it above with your own input.
What does this Hexadecimal Number regex match?
This pattern matches: "0xFF00FF". It does NOT match: "0xGG". 0x literals, memory addresses, byte strings, CSS color validation, binary data representation.
Is the Hexadecimal Number regex beginner-friendly?
This pattern is rated Beginner. It uses basic regex syntax and is easy to understand.
What languages support the Hexadecimal Number regex?
This pattern works in all major programming languages including JavaScript, Python, Java, C#, Go, Ruby, PHP, and more. Syntax may vary slightly between regex engines.
Can I modify the Hexadecimal Number regex for my use case?
Yes! Use the interactive tester above to modify the pattern and test with your own data. Common modifications include making it case-insensitive (add 'i' flag), matching globally (add 'g' flag), or adjusting character classes.