Text Processing

Positive Lookahead (Password)

Use positive lookahead `(?=...)` to require the password contain at least one digit and one uppercase letter.

Try it in RegexPro →

Available in

JSSupported

JavaScript / ECMAScript

Browser-native RegExp. Default if you don't pick.

PYSupported

Python (re)

CPython stdlib `re`. Unicode-aware `\w` and `\d` by default.

GOSee workaround

Go (RE2)

Linear-time matching. No backreferences or lookarounds.

Pattern

regexengine-agnostic
^(?=.*\d)(?=.*[A-Z])[A-Za-z\d]{8,}$

Raw source: ^(?=.*\d)(?=.*[A-Z])[A-Za-z\d]{8,}$

How it works

(?=.*\d) is a zero-width assertion that requires the rest of the string to contain a digit somewhere. (?=.*[A-Z]) similarly requires an uppercase letter. Neither consumes characters. [A-Za-z\d]{8,}$ then matches the actual password content (≥8 alphanumerics). Lookaheads are supported in JS and Python; Go's RE2 does NOT support them.

Examples

Input

Password1

Matches

  • Password1

Input

weakpass

No match

—

Input

ALLCAPSNODIGIT

No match

—

Common use cases

  • •Password complexity enforcement
  • •Form validation with multiple co-required tokens
  • •Filename validation (must end with extension AND start with letter)
  • •Compound-rule input filtering
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