Pattern

Regex for JSON key

Quoted JSON object key (a property name).

The JSON key regex is "([^"\\]|\\.)*"\s*: — copy it below, or open it in the explainer for a token-by-token breakdown.

The pattern

"([^"\\]|\\.)*"\s*:

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What it matches

"name":
"first_name" :
"with\"escape":

What it doesn't match

name:
"unclosed
42 :

Notes & gotchas

Matches a JSON-style double-quoted key followed by colon. Handles escaped quotes inside the key. For full JSON parsing use JSON.parse — this is just for find-in-text.

Code in your language

Use the explainer's Code tab to generate ready-to-paste snippets in JavaScript, Python, Java, .NET, Go, Ruby, and PHP for this pattern.

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Token-by-token breakdown

Every part of the pattern, left to right:

Token	Meaning
`"`	literal text “"”
`(`	start of a capturing group
`[^"\\]`	any character except “"”, “\”
`\|`	OR — try the alternative
`\\`	literal “\”
`.`	any character (except newline)
`)*`	end of group, zero or more
`"`	literal text “"”
`\s*`	zero or more: whitespace
`:`	literal text “:”

About this pattern

Developer-oriented patterns help with code analysis, log parsing, and data transformation. Use these in build scripts, CI tools, IDE search-and-replace, and code review utilities.

Quick usage in different languages

This exact pattern — with the correct escaping and idioms for each language:

JavaScript: /"([^"\\]|\\.)*"\s*:/.test(value)
Python: re.match(r'"([^"\\]|\\.)*"\s*:', value)
Java: Pattern.compile("\"([^\"\\\\]|\\\\.)*\"\\s*:").matcher(value).matches()
C# / .NET: Regex.IsMatch(value, @"""([^""\\]|\\.)*""\s*:")
Go: regexp.MustCompile(`"([^"\\]|\\.)*"\s*:`).MatchString(value)
Ruby: /"([^"\\]|\\.)*"\s*:/.match?(value)
PHP: preg_match('~"([^"\\]|\\.)*"\s*:~', $value)

The explainer’s Code tab regenerates these for any pattern you paste, and the downloadable cheat sheet bundles the breakdown, all seven snippets, and the pitfalls below onto one printable page.

Common pitfalls

Not anchored. Without ^ and $ this can match a substring anywhere in the input — add anchors if you need the whole value to conform.
Watch for backtracking. This pattern nests quantifiers; on adversarial input that can cause exponential backtracking (ReDoS). Test with long non-matching strings, or use an RE2-based engine.
Escape it correctly per language. In Java and JavaScript strings each backslash must be doubled (\\d); in Python, Go, and C# use raw/verbatim strings so the backslashes survive.
Validate beyond format. Matching the format doesn't guarantee the value is real. Confirm the json key against a source of truth (database, API, or checksum) where it matters.

Standards & sources

This pattern is based on the following authoritative specification(s) and issuing authorities. Formats can change — always confirm against the primary source.

RFC 8259 — The JavaScript Object Notation (JSON)

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