Pattern

Regex for Binary number with 0b prefix

Binary literal: 0b101010.

The Binary number with 0b prefix regex is ^0[bB][01]+$ — copy it below, or open it in the explainer for a token-by-token breakdown.

The pattern

^0[bB][01]+$

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Token-by-token breakdown

Every part of the pattern, left to right:

Token	Meaning
`^`	start of string (or line in multiline mode)
`0`	literal text “0”
`[bB]`	any of: “b”, “B”
`[01]+`	one or more: any of: “0”, “1”
`$`	end of string (or line in multiline mode)

About this pattern

Number patterns appear constantly in form validation, log parsing, and data extraction. Regex is great for matching the shape but limited for semantic checks (range validation, mathematical constraints).

Quick usage in different languages

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

JavaScript: /^0[bB][01]+$/.test(value)
Python: re.match(r"^0[bB][01]+$", value)
Java: Pattern.compile("^0[bB][01]+$").matcher(value).matches()
C# / .NET: Regex.IsMatch(value, @"^0[bB][01]+$")
Go: regexp.MustCompile(`^0[bB][01]+$`).MatchString(value)
Ruby: /^0[bB][01]+$/.match?(value)
PHP: preg_match('~^0[bB][01]+$~', $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

Anchored to the whole string. This pattern uses ^ and $, so it requires the entire input to match. To find it inside a longer text, drop the anchors and use the global (g) flag.
Validate beyond format. Matching the format doesn't guarantee the value is real. Confirm the binary number with 0b prefix against a source of truth (database, API, or checksum) where it matters.

Related patterns

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