# unicorn/escape-case

> Require uppercase hexadecimal digits in escape sequences

`"\xa9"` and `"\xA9"` are the same string. With uppercase digits the value stands out from the lowercase `x` or `u` before it, and the same character is written the same way everywhere, so you can search for it.

The rule checks `\x`, `\u` and `\u{...}` escapes in strings, template literals and regular expressions, and the letter in `\c` escapes in regular expressions. ``String.raw`...` `` isn't checked.

`--fix` changes the digits to uppercase.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"unicorn/escape-case" = "error" # or "warn"
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 4} */}
```js
const copyright = "\xa9 2026";
const price = `${amount}\u00a0EUR`;
const smile = "\u{1f600}";
const escape = /\x1b\[\d+m/;
```

Not reported:

{/* good */}
```js
const copyright = "\xA9 2026";
const price = `${amount}\u00A0EUR`;
const smile = "\u{1F600}";
const escape = /\x1B\[\d+m/;
```

{/* good */}
```js
const source = String.raw`\xa9`;
```