Bad escaped character in JSON / Invalid \escape

What the error means

Inside a JSON string, a backslash must start one of nine escapes: \" \\ \/ \b \f \n \r \t, or \u followed by exactly four hexadecimal digits. Any other character after a backslash is invalid. The usual sources are Windows paths such as C:\Users, regular expressions such as \d, and \' copied from JavaScript or SQL strings. A \u escape without four hex digits has its own Unicode-escape message.

Exact messages by runtime

Messages depend on the input and runtime version. Node and Python rows were reproduced locally. Other rows cite official documentation or source. Rows marked as fragments or templates preserve the source wording and are not complete exception transcripts. Browsers and libraries may append location details.

Causes you can reproduce

const text = String.raw`{"path":"C:\Users\ada"}`;
JSON.parse(text);
// Bad escaped character in JSON at position 12

import json
json.loads(r'{"pattern": "\d+"}')
# Invalid \escape: line 1 column 14 (char 13)

JSON.parse(String.raw`{"name":"O\'Brien"}`);
// Bad escaped character in JSON at position 11

How to fix it

1. Find the backslash at the reported position. V8 and Firefox point at the character after it; Python points at the backslash itself.
2. Decide what the value should contain. A literal backslash, as in a path or a pattern, needs two backslashes in JSON text. A backslash that only escaped an apostrophe in another language should be removed.
3. Fix the producer: serialize the original string with JSON.stringify, json.dumps or your platform serializer instead of inserting raw text between quotes.
4. Watch the source-code layer too. In JavaScript and Python a backslash in an ordinary string literal is already an escape, so JSON written by hand in code needs String.raw or a Python raw string.

const value = { path: 'C:\\Users\\ada', pattern: '\\d+', name: "O'Brien" };
const text = JSON.stringify(value);
console.log(text); // {"path":"C:\\Users\\ada","pattern":"\\d+","name":"O'Brien"}
console.log(JSON.parse(text).path); // C:\Users\ada

import json
value = {"path": r"C:\Users\ada", "pattern": r"\d+"}
text = json.dumps(value)
print(text)  # {"path": "C:\\Users\\ada", "pattern": "\\d+"}
assert json.loads(text) == value

Find the exact position with Tool Kumar

1. Copy the exact input text, including its original whitespace. For HTTP failures, copy the raw response body.
2. Open the Tool Kumar JSON validator and paste the text. The document stays in your browser.
3. Read the line and column in the error or fixable-issue banner. For an invalid document, select Go to error to move the caret to that location.
4. Inspect the preceding token as well as the marked character. A parser marks where it discovered the problem; the missing quote, separator or value can start earlier.

Python character offsets are zero-based, while its displayed lines and columns are one-based. V8 string positions count UTF-16 code units; Go offsets count bytes read. Unicode text can make these offsets differ. Use the original text and its line/column context rather than copying an offset between runtimes.

Tool Kumar can classify some input as fixable loose JSON. Review a proposed change before using the JSON repair tool, then validate the result against your API contract. For empty input, inspect the producer or response because there is no character to select.

Frequently asked questions

Related errors and tools

• Bad control character in string literal in JSON
• Expecting ',' delimiter / Expected ',' or '}' after property value
• Expecting property name enclosed in double quotes
• All JSON error guides
• JSON syntax reference

Standards and diagnostic sources

RFC 8259 and ECMA-404 define JSON syntax. Diagnostic wording belongs to the parser. The table links each cited message to its source.

• MDN JSON.parse error reference
• Python json documentation and JSONDecodeError attributes
• WebKit source for the JSON Parse error prefix