Describe it in English. Get a tested regex.

Email address

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

Matches a standard email address such as name@example.com.

URL (http/https)

^https?://[^\s/$.?#].[^\s]*$

Matches an http or https web URL.

US phone number

^(\+1[-.\s]?)?\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}$

Matches a US phone number, optionally with +1 and separators.

China mobile phone number

^1[3-9]\d{9}$

Matches a mainland China 11-digit mobile number.

IPv4 address

^((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)$

Matches a valid IPv4 address (0-255 per octet).

ISO date (YYYY-MM-DD)

^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$

Matches an ISO 8601 calendar date like 2026-07-13.

24-hour time (HH:MM)

^([01]\d|2[0-3]):[0-5]\d$

Matches 24-hour clock time such as 09:30 or 23:59.

Hex color code

^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$

Matches a #RGB or #RRGGBB hex color code.

UUID (v4-ish)

^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$

Matches an RFC-4122 UUID string.

URL slug

^[a-z0-9]+(?:-[a-z0-9]+)*$

Matches a lowercase URL slug like my-blog-post.

Username (3-16, alnum/underscore)

^[a-zA-Z0-9_]{3,16}$

Matches a username of 3-16 letters, digits or underscores.

Strong password

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^\w\s]).{8,}$

Requires 8+ chars with lower, upper, digit and symbol.

Integer (signed)

^[+-]?\d+$

Matches an optionally signed whole number.

Decimal number

^[+-]?(\d+\.?\d*|\.\d+)$

Matches an optionally signed decimal number.

Hashtag

^#[A-Za-z0-9_]+$

Matches a social media hashtag like #OpenAI.

US ZIP code

^\d{5}(-\d{4})?$

Matches a US ZIP or ZIP+4 postal code.

IPv6 address (full form)

^([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}$

Matches a fully written (uncompressed) IPv6 address.

MAC address

^([0-9A-Fa-f]{2}[:-]){5}[0-9A-Fa-f]{2}$

Matches a MAC hardware address with : or - separators.

Credit card number

^\d{13,16}$

Matches a 13-16 digit credit card number (format only).

12-hour time (with AM/PM)

^(0?[1-9]|1[0-2]):[0-5]\d\s?([AaPp][Mm])$

Matches a 12-hour clock time such as 09:30 AM or 12:00pm.

US date (MM/DD/YYYY)

^(0[1-9]|1[0-2])/(0[1-9]|[12]\d|3[01])/\d{4}$

Matches a US-format date like 07/13/2026.

Semantic version

^\d+\.\d+\.\d+$

Matches a semantic version number like 1.2.3.

Domain name

^([a-zA-Z0-9](-?[a-zA-Z0-9])*\.)+[a-zA-Z]{2,}$

Matches a bare domain name like example.com.

US currency amount

^\$\d{1,3}(,\d{3})*(\.\d{2})?$

Matches a US dollar amount like $1,000.00.

Decimal with 2 places

^\d+\.\d{2}$

Matches a number with exactly two decimal places.

No whitespace

^\S+$

Matches a string containing no whitespace characters.

Alphanumeric only

^[a-zA-Z0-9]+$

Matches letters and digits only (no symbols or spaces).

HTML opening tag

^<[a-zA-Z][a-zA-Z0-9]*(\s[^>]*)?>$

Matches an HTML opening tag such as <div> or <a href='x'>.

Positive integer

^[1-9]\d*$

Matches a positive whole number with no leading zero.

Hexadecimal number

^0[xX][0-9a-fA-F]+$

Matches a hex literal like 0x1A3F.