Regex Tester & Validator

Matches sequences of 13 to 16 digits, allowing spaces or hyphens between digits (non-greedy). Commonly used to identify credit card numbers in text, but also applicable to other long numeric identifiers. The pattern is tolerant of common formatting like '1234 5678 9012 3456' or '1234-5678-9012-3456'. Works with multiline text due to gm flags.