Regex (?=...) — Positive Lookahead

(?=...) is a positive lookahead that matches a position where the pattern ... follows, without consuming those characters. Example: /foo(?=\d)/ matches "foo" only when a digit follows.

Key facts

Frequently asked questions

What is a positive lookahead?

An assertion that the following text matches, without consuming it.

Lookahead vs lookbehind?

Lookahead (?=...) checks ahead; lookbehind (?<=...) checks behind.

Related pages

• HTTP 200 OK
• HTTP 301 Moved Permanently
• HTTP 401 Unauthorized
• HTTP 403 Forbidden
• HTTP 404 Not Found
• HTTP 429 Too Many Requests
• HTTP 500 Internal Server Error
• HTTP 502 Bad Gateway

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