Regex Tester & Validator

Matches an opening HTML tag in JavaScript: a literal `<`, one alphanumeric character, an optional space, then any content lazily (including newlines via the `s` flag) up to the first `>`. Useful for extracting tags like `<div>`, `<a href="...">`, or `<span>` during HTML parsing, validation, or sanitization. Caveats: the lazy dot also permits self-closing forms such as `<br/>`, and with dotall enabled it can match across multiple lines.