JavaScript RegExp \xHH Hex Escape

What Is \xHH?

\xHH matches one character by its two-digit hexadecimal byte value (0x00–0xFF). It covers ASCII letters, digits, and control characters such as newline (\x0A) and tab (\x09).

\xHH     → character at hex byte HH

\x41     → "A"   (65 decimal)
\x0A     → newline  (same as \n)
\x09     → tab      (same as \t)
\x20     → space

exactly 2 hex digits (pad with 0)
range: 0x00 … 0xFF

How to Use \xHH

Write two hex digits after \x, then test or match as usual.

1. Pick the character’s byte value in hex (0–FF). Pad with a leading zero if needed.
2. Put \xHH in a regex literal or RegExp pattern — e.g. /\x41/.
3. Call test, match, or split on your string.
4. For common controls, prefer \n / \t when readability matters; use hex when a spec lists 0xNN codes.

Pseudocode

pattern contains "\x" + HH   // HH = two hex digits

byte = parse_hex(HH)         // 0 … 255
target = character(byte)

for each char in input:
    if char == target:
        match this position
    else:
        try next / fail

Cheat Sheet

Keep these hex escapes handy while writing patterns.

Live Preview

Pick a hex escape and see what character it matches against a sample string.

/\x41/.test("ABC")
→ true

/* 0x41 = 65 = "A" */

JavaScript Examples

Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.

console.log(/\x41/.test("A"));    // true
console.log(/\x41/.test("B"));    // false
console.log(/\x41/.test("ABC"));  // true

true
false
true

const text = "line1\nline2";
const row = "name\tage";

console.log(/\x0A/.test(text));   // true
console.log(text.split(/\x0A/));  // ["line1", "line2"]
console.log(/\x09/.test(row));    // true
console.log(row.split(/\x09/));   // ["name", "age"]

true
[ 'line1', 'line2' ]
true
[ 'name', 'age' ]

const text = "Room 25B has code 99";
console.log(text.match(/[\x30-\x39]+/g));  // ["25", "99"]

const ch = "A";
console.log(/\x41/.test(ch));    // true
console.log(/\u0041/.test(ch));  // true

[ '25', '99' ]
true
true

Performance Notes

Hex escapes are resolved when the pattern is compiled. At match time they behave like a single literal character — no extra runtime cost versus writing A or \n directly.

Key Takeaways