Pattern

Regex for Ethereum address

0x + 40 hex characters Ethereum address.

The Ethereum address regex is ^0x[a-fA-F0-9]{40}$ — copy it below, or open it in the explainer for a token-by-token breakdown.

The pattern

^0x[a-fA-F0-9]{40}$

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What it matches

0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb1
0x0000000000000000000000000000000000000000

What it doesn't match

742d35Cc6634C0532925a3b844Bc9e7595f0bEb1
0x123

Notes & gotchas

Ethereum addresses are 40 hex chars (20 bytes) with 0x prefix. Case is meaningful in EIP-55 checksum format but lowercase is also valid (no checksum). Same format used by EVM chains: Polygon, BSC, Avalanche, Arbitrum, etc.

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
`^`	start of string (or line in multiline mode)
`0x`	literal text “0x”
`[a-fA-F0-9]{40}`	exactly 40 times: any of: a–f, A–F, digits
`$`	end of string (or line in multiline mode)

About this pattern

Identifier formats like UUIDs, hashes, and version strings have well-defined structures that regex captures cleanly. The pattern verifies format; checksums and validity against a registry need additional checks.

Quick usage in different languages

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

JavaScript: /^0x[a-fA-F0-9]{40}$/.test(value)
Python: re.match(r"^0x[a-fA-F0-9]{40}$", value)
Java: Pattern.compile("^0x[a-fA-F0-9]{40}$").matcher(value).matches()
C# / .NET: Regex.IsMatch(value, @"^0x[a-fA-F0-9]{40}$")
Go: regexp.MustCompile(`^0x[a-fA-F0-9]{40}$`).MatchString(value)
Ruby: /^0x[a-fA-F0-9]{40}$/.match?(value)
PHP: preg_match('~^0x[a-fA-F0-9]{40}$~', $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.
Case sensitivity. Letter ranges are case-sensitive — use the i flag if the input case can vary.
Validate beyond format. Matching the format doesn't guarantee the value is real. Confirm the ethereum address 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.

EIP-55 — Mixed-case checksum address encoding (Ethereum)

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