Handling Special Characters in JSON Strings

If you are asking what special characters JSON does not accept, the practical answer is short: inside a JSON string, raw double quotes, raw backslashes, and ASCII control characters from U+0000 through U+001F are not allowed as-is. They must be escaped. JSON also rejects made-up escape sequences such as \', \x41, or \v.

Everything else is less mysterious than it looks. Most punctuation is fine, single quotes are fine as data, forward slashes do not need escaping, and Unicode text such as accented letters, CJK characters, and emoji can appear directly in a valid JSON string.

Which characters are valid in JSON strings?

Per the current JSON specification, a string can contain any Unicode character except an unescaped double quote, an unescaped backslash, or characters in the U+0000 to U+001F range. That means most symbols people worry about, including @, #, % , &, *, <, >, and ', are fine in string values without extra escaping.

Valid escape sequences in JSON

JSON has a small, fixed escape set. If you put a backslash before some other character, the parser should reject it as a bad escape. This is one of the biggest differences between JSON and language string literals.

Common mistakes and how to fix them

1. Unescaped quotes inside a string

A raw double quote ends the JSON string early, so it must be escaped as \".

{
  "message": "He said "hello" to me"
}

{
  "message": "He said \"hello\" to me"
}

2. Backslashes in paths and regular expressions

A backslash is always special in JSON. If you want a literal backslash in the resulting value, write it as \\. This is why Windows paths often break when copied into JSON.

{
  "path": "C:\Users\sam\Documents\report.json"
}

{
  "path": "C:\new\test"
}

{
  "path": "C:\\Users\\sam\\Documents\\report.json"
}

3. Raw line breaks and tabs

JSON does not support multiline strings with literal line breaks inside the quotes. Use escaped control characters instead.

{
  "description": "Line one
Line two"
}

{
  "description": "Line one\nLine two"
}

4. Escaping characters that JSON never asked you to escape

This is where many developers mix up JSON with JavaScript, Python, or shell escaping. In JSON, an apostrophe does not need escaping because strings are delimited by double quotes. Writing \' creates a bad escape. The same applies to \x41, \v, and \0.

5. Single quotes around strings or object keys

JSON is stricter than JavaScript object literal syntax. Both string values and property names must use double quotes. This is invalid JSON:

{
  'message': 'hello'
}

Does JSON accept Unicode, accented characters, and emoji?

Yes. Direct Unicode characters are valid in JSON strings, and escaped Unicode is also valid. If you escape a character outside the basic multilingual plane, use a surrogate pair such as \uD83D\uDE80 for the rocket emoji.

{
  "greeting": "こんにちは",
  "heartDirect": "I ❤️ JSON",
  "heartEscaped": "I \u2764\uFE0F JSON",
  "rocketEscaped": "\uD83D\uDE80"
}

Common parser errors and what they usually mean

Different parsers phrase errors differently, but the same patterns show up again and again. If your formatter or parser reports one of the following, check the matching issue first.

The safest way to avoid escaping mistakes

The best fix is usually not to hand-edit JSON at all. Build a normal data structure in your language and let a JSON serializer escape the string content for you.

const payload = {
  message: 'He said "hello" to me',
  path: "C:\\Users\\sam\\Documents\\report.json",
  description: "Line one\nLine two"
};

const json = JSON.stringify(payload);

1. Use a real JSON library or serializer instead of concatenating strings by hand.
2. Validate copied JSON before shipping it, especially when it contains paths, HTML, or multiline content.
3. Remember that a backslash can make JSON invalid or silently change the value you meant to store.
4. Prefer UTF-8 JSON for interchange and keep binary data out of strings unless you intentionally encode it.

For search users landing here directly, the main rule to remember is simple: JSON accepts almost all visible characters in strings, but it is very strict about quotes, backslashes, and low-value control characters. Once you know that small rule set, most "special character" bugs become easy to spot.