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jsonbeautifiers
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V8 Verified by running the parser on Node v24.15.0, V8 13.6.233.17.

Bad escaped character in JSON at position N (line L column C)

JSON allows exactly nine escape sequences: \" \\ \/ \b \f \n \r \t and \uXXXX. Anything else after a backslash is an error. A single backslash in a Windows path is almost always the cause, because \U, \P and \D are not escapes.

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Input

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What actually causes it

Ranked by how often each one turns out to be the answer.

  1. 01 A Windows file path with single backslashes

    This is the dominant cause. Every backslash in a JSON string must be doubled. Forward slashes also work on Windows in most contexts and avoid the problem entirely.

    Breaks

    { "path": "C:\Users\priya\config.json" }

    Works

    { "path": "C:\\Users\\priya\\config.json" }

  2. 02 A hex escape borrowed from another language

    JSON has no \x escape. C, Python and JavaScript all accept \x41 for the letter A; JSON requires \u0041.

    Breaks

    { "c": "\x41" }

    Works

    { "c": "\u0041" }

  3. 03 A regular expression pasted into a string

    Patterns like \d, \s and \w are not JSON escapes. Every backslash in the pattern needs doubling before it goes into a JSON string.

    Breaks

    { "pattern": "^\d{3}-\d{4}$" }

    Works

    { "pattern": "^\\d{3}-\\d{4}$" }

  4. 04 A single-quote escape

    \' is valid in JavaScript and JSON5 but not in JSON. Inside a double-quoted string an apostrophe needs no escape at all.

The same mistake in other runtimes

The underlying problem is identical; only the wording differs. If a colleague reports one of these, they are looking at the same thing you are.

Python Invalid \escape: line 1 column 9 (char 8)

Questions

Why does my Python string look right but still fail?
Because the backslash is consumed twice: once by the Python string literal and once by JSON. Use a raw string for the literal, or build the object and call json.dumps rather than writing JSON by hand.
Is \/ really allowed?
Yes. Escaping a forward slash is optional in JSON and both forms mean the same character. It exists so that JSON can be safely embedded inside a script tag in HTML, where the sequence </ would end the element.

Fix it now

Paste the payload into the tool above, or go straight to the one built for this job.

Escape a string correctly