Regex Library

^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$

Base64 String Regex

Matches a standard Base64-encoded string, enforcing the correct alphabet, length multiple of four, and valid padding.

^(?=.*[A-Za-z])(?=.*\d)[A-Za-z0-9]{6,20}$

Basic Password Regex

Validates a simple password policy: 6-20 alphanumeric characters containing at least one letter and one digit, with no special-character or mixed-case requirements.

^Bearer\s+[A-Za-z0-9\-_.]+$

Bearer Token Regex

Matches the value of an HTTP Authorization header using the Bearer scheme, such as 'Bearer <token>'.

Binary Number Regex

Validates that a string contains only the digits 0 and 1, i.e. a well-formed binary (base-2) number.

^[01]+$

^[a-z][a-z0-9]*(?:[A-Z][a-z0-9]*)*$

camelCase Identifier Regex

Validates that a string is a lowerCamelCase identifier: it starts with a lowercase letter and each subsequent word begins with a single uppercase letter followed by lowercase letters or digits.

^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|3[47][0-9]{13}|6(?:011|5[0-9]{2})[0-9]{12})$

Credit Card Number Regex

Validates the digit-only format of major credit card numbers by issuer prefix and length, covering Visa, MasterCard, American Express, and Discover.

^\.-?[_a-zA-Z][_a-zA-Z0-9-]*$

CSS Class Selector Regex

Validates a single CSS class selector: a leading dot followed by a legal CSS identifier, such as .btn, .btn-primary, or .btn_2, using ASCII letters, digits, underscores, and hyphens.

CSS Comment Regex

Detects a CSS comment, /* ... */, using a lazy quantifier so the match stops at the first closing */ instead of spanning all the way to the last one in the stylesheet.

/\*[\s\S]*?\*/

CVV / CVC Code Regex

Validates a card verification value (CVV/CVC/CID) as exactly three or four digits, matching the security code formats used by Visa, Mastercard, and American Express.

^[0-9]{3,4}$

^(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,63}$

Decimal Number Regex

Validates a fixed-point decimal number that requires digits on both sides of the decimal point, with an optional leading minus sign.

^-?\d+\.\d+$

MediumNetworking

Domain Name Regex

Validates a fully qualified domain name made of one or more dot-separated labels followed by an alphabetic top-level domain, rejecting labels that start or end with a hyphen.

EasyNetworking

Domain with TLD Regex

Validates a domain name that ends in a letters-only top-level domain of two or more characters, such as example.com, example.co.uk, or www.example.com.

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

Duplicate Spaces Regex

Matches two or more consecutive literal space characters, commonly used to collapse extra spacing down to a single space.

[ ]{2,}

^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$

Email Regex

Validates common email address formats by requiring a local part, an @ symbol, a domain, and a top-level domain of at least two letters.

HardText Processing

Emoji Regex

Matches a single emoji character using the Unicode Extended_Pictographic property, which requires the u (or v) flag for Unicode property escapes.

\p{Extended_Pictographic}

EasyFiles

File Extension Regex

Extracts and validates the file extension of a filename, requiring at least one character before the final dot.

^.+\.([a-zA-Z0-9]+)$

Float Number Regex

Validates a floating-point literal that always contains a decimal point, allowing the digits before or after it to be omitted, similar to how many programming languages parse float literals.

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

^[A-Za-z_][A-Za-z0-9_]*$[^)]*$$

Function Call / Name Regex

Matches a simple function-call-shaped string: a valid identifier immediately followed by a parenthesized, non-nested argument list, such as foo() or add(a, b).

^(?:[a-zA-Z0-9]+_)*[A-Za-z0-9]{32,}$

Generic API Key Regex

Matches a generic API key shape: an optional underscore-separated prefix like sk_live_ followed by a 32-character or longer alphanumeric token.

^[a-zA-Z_][a-zA-Z0-9_]*$

Generic Variable Name Regex

Validates a generic variable name shared by most C-family and scripting languages: it must start with a letter or underscore, followed by any number of letters, digits, or underscores.

^https?:\/\/(?:www\.)?github\.com\/([\w.-]+)\/([\w.-]+)(?:\/.*)?$

GitHub URL Regex

Matches a GitHub repository URL and captures the owner and repository name, optionally allowing a deeper path like a file or branch.

^#[A-Za-z][A-Za-z0-9_]*$

Hashtag Regex

Validates a social-media style hashtag: a leading # symbol followed by a letter and then any combination of letters, digits, and underscores.

EasyWeb

Hex Color Code Regex

Validates a CSS hex color code in either the six-digit (#RRGGBB) or shorthand three-digit (#RGB) form.

^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$

^[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$

Hexadecimal Number Regex

Validates a base-16 (hexadecimal) number that must be written with an explicit '0x' or '0X' prefix, followed by one or more hex digits.

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

EasyNetworking

Hostname Regex

Validates an RFC 1123 style hostname made of one or more dot-separated labels, where every label starts and ends with an alphanumeric character and may contain interior hyphens.

^[a-zA-Z_:][-a-zA-Z0-9_:.]*(?:\s*=\s*(?:"[^"]*"|'[^']*'|[^\s"'=<>`]+))?$

HTML Attribute Regex

Validates a single HTML attribute, matching a boolean attribute name on its own (like disabled), or a name=value pair using double-quoted, single-quoted, or unquoted attribute values.

HTML Comment Regex

Detects an HTML comment, , using a lazy quantifier so the match stops at the first closing --> instead of swallowing everything up to the last one in the document.

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

HTML Tag Regex

Finds opening and closing HTML tags such as <div>, </span>, or <br/> by matching an angle bracket, an optional slash, a tag name, and any attributes up to the closing bracket.

EasyWeb

Image URL Regex

Matches an absolute HTTP or HTTPS URL that ends in a common image file extension, with an optional query string.

^https?:\/\/\S+\.(?:jpg|jpeg|png|gif|webp|svg|bmp|avif)(?:\?\S*)?$

HardInternational

Indian GSTIN Regex

Validates the structural format of a 15-character Indian GST Identification Number (GSTIN): state code, embedded PAN, entity code, the fixed letter Z, and a checksum character.

^[0-9]{2}[A-Z]{5}[0-9]{4}[A-Z]{1}[1-9A-Z]{1}Z[0-9A-Z]{1}$

^[A-Z]{5}[0-9]{4}[A-Z]$

Indian PAN Number Regex

Validates the format of an Indian Permanent Account Number (PAN): five uppercase letters, four digits, and a final uppercase letter, e.g. ABCDE1234F.

Indian PIN Code Regex

Validates a 6-digit Indian postal PIN code, requiring the first digit to be 1-9 since no PIN code region starts with 0.

^[1-9][0-9]{5}$

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

Integer Regex

Validates a whole number with an optional leading minus sign, disallowing decimal points and unnecessary leading zeros.

^-?(0|[1-9]\d*)$

EasyNetworking

IPv4 Address Regex

Validates a dotted-quad IPv4 address, ensuring each of the four octets is a number between 0 and 255 with no leading zeros.

HardNetworking

IPv4 CIDR Notation Regex

Validates an IPv4 address in CIDR notation, ensuring each of the four octets falls within 0-255 and the prefix length after the slash falls within 0-32.

^(?:(?: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)\/(?:3[0-2]|[12]?\d)$

HardNetworking

ISBN-10 / ISBN-13 Regex

Validates the compact, unformatted length and character shape of an ISBN-10 (9 digits plus a final digit or X) or an ISBN-13 (13 digits), without hyphens or spaces.

^(?:\d{9}[\dX]|\d{13})$

ISO 3166-1 Alpha-2 Country Code Regex

Validates that a string has the shape of an ISO 3166-1 alpha-2 country code: exactly two uppercase letters, such as US, GB, or IN.

^[A-Z]{2}$

ISO 4217 Currency Code Regex

Validates that a string has the shape of an ISO 4217 currency code: exactly three uppercase letters, such as USD, EUR, or INR.

^[A-Z]{3}$

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

ISO 639-1 / BCP-47 Language Code Regex

Validates an ISO 639-1 two-letter language code, optionally followed by a BCP-47 style region subtag such as en-US or zh-CN.

^[a-z]{2}(-[A-Z]{2})?$

EasyDates

ISO 8601 Date Regex

Validates a calendar date in ISO 8601 YYYY-MM-DD format, checking that the month is 01-12 and the day is 01-31.

MediumDates

ISO 8601 Time Regex

Validates a 24-hour ISO 8601 time-of-day string in HH:MM:SS format, with an optional fractional-seconds component of up to three digits.

^([01]\d|2[0-3]):[0-5]\d:[0-5]\d(\.\d{1,3})?$

^[A-Za-z_$][A-Za-z0-9_$]*$

Java Identifier Regex

Validates that a string is a syntactically legal Java identifier: it must start with a letter, underscore, or dollar sign, followed by any number of letters, digits, underscores, or dollar signs.

MediumProgramming

JavaScript Comment Regex

Detects a JavaScript comment, either a single-line // comment or a block /* ... */ comment, using a lazy quantifier on the block form so it stops at the first closing */ instead of the last one.

\/\/.*|\/\*[\s\S]*?\*\/

^(?:"(?:[^"\\]|\\.)*"|-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?|true|false|null)$

JSON Value Token Regex

Matches a single JSON scalar value: a double-quoted string, a JSON-formatted number, or one of the literals true, false, or null.

^[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+$

JWT (JSON Web Token) Regex

Checks that a string has the three-part, dot-separated base64url shape of a JSON Web Token (header.payload.signature) without decoding or verifying the signature.

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

kebab-case Identifier Regex

Validates that a string is a lower kebab-case identifier: lowercase words separated by single hyphens, with no leading, trailing, or doubled hyphens.

^-?(90(\.0+)?|[1-8]?[0-9](\.[0-9]+)?)$

Latitude Regex

Validates a decimal latitude value within the real-world range of -90 to 90 degrees, with an optional fractional component of any precision.

HardInternational

Latitude/Longitude Coordinate Pair Regex

Validates a comma-separated 'latitude,longitude' coordinate pair, enforcing the real-world ranges of -90 to 90 for latitude and -180 to 180 for longitude.

^-?(90(\.0+)?|[1-8]?[0-9](\.[0-9]+)?),\s*-?(180(\.0+)?|1[0-7][0-9](\.[0-9]+)?|[1-9]?[0-9](\.[0-9]+)?)$

Line Ending (Newline) Regex

Matches a single line ending in any common style: Windows CRLF (\r\n), classic Mac CR (\r), or Unix LF (\n).

\r\n|\r|\n

^https?:\/\/(?:www\.)?linkedin\.com\/(?:in|company|pub)\/[\w-]+\/?$

LinkedIn URL Regex

Matches a LinkedIn personal profile, company page, or legacy public profile URL.

^-?(180(\.0+)?|1[0-7][0-9](\.[0-9]+)?|[1-9]?[0-9](\.[0-9]+)?)$

Longitude Regex

Validates a decimal longitude value within the real-world range of -180 to 180 degrees, with an optional fractional component of any precision.

MediumNetworking

MAC Address Regex

Validates a 48-bit MAC address written as six hexadecimal byte pairs separated by colons or hyphens, such as 00:1A:2B:3C:4D:5E.

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

MediumText Processing

Markdown Link Regex

Matches Markdown link syntax [text](url) and captures the link text and destination, with optional support for a quoted title.

\[([^\]]+)\]$([^)\s]+)(?:\s+"[^"]*")?$

^[a-zA-Z0-9!#$&^_.+-]+\/[a-zA-Z0-9!#$&^_.+-]+$

Mention Handle Regex

Validates a social-media style @mention handle: an @ symbol followed by 1 to 15 letters, digits, or underscores, matching common username length limits.

^@[A-Za-z0-9_]{1,15}$

EasyFiles

MIME Type Regex

Matches a MIME type string in the form type/subtype, such as text/html or application/json, including structured suffixes like +json.

^(?:\+\d{1,3}[-\s]?)?\d{10}$

Mobile Number Regex

Validates a 10-digit mobile number with an optional international dialing prefix such as +91 or +1, allowing a single space or hyphen between the country code and the number.

Octal Number Regex

Validates a base-8 (octal) number, accepting digits 0-7 with an optional case-insensitive '0o' prefix as used by modern language literals.

^(0o)?[0-7]+$

One-Time Password (OTP) Regex

Validates that a string is a numeric one-time password between 4 and 8 digits long, matching the typical range used by SMS, email, and authenticator-app OTPs.

^\d{4,8}$

Passport Number Regex

Validates a generic international passport number shape: a leading letter followed by 5 to 8 more letters or digits, for a total length of 6 to 9 alphanumeric characters.

^[A-Z][A-Z0-9]{5,8}$

Percentage Regex

Validates a percentage value: a signed integer or decimal number immediately followed by a trailing percent sign.

^-?\d+(\.\d+)?%$

^\+?1?[-.\s]?$?([0-9]{3})$?[-.\s]?([0-9]{3})[-.\s]?([0-9]{4})$

Phone Number Regex

Validates common North American phone number formats, accepting optional country code, parentheses, dots, dashes, or spaces as separators.

^\/\/[\w-]+(\.[\w-]+)+(:\d+)?(\/[^\s]*)?$

Protocol-Relative URL Regex

Validates a protocol-relative URL that omits the scheme and starts with //, such as //example.com/path, which inherits http or https from the page that references it.

^[A-Za-z_][A-Za-z0-9_]*$

Python Identifier Regex

Validates that a string is a syntactically legal Python identifier: it must start with an ASCII letter or underscore, followed by any number of letters, digits, or underscores.

^\/(?!\/)[\w\-\/.]*(\?[^\s#]*)?(#[^\s]*)?$

Relative URL Regex

Validates a root-relative URL path such as /path/to/page, including an optional query string and fragment, while rejecting protocol-relative (//host) and absolute URLs.

HardNumbers

Roman Numerals Regex

Validates well-formed Roman numerals from 1 to 3999 written with standard subtractive notation (e.g. IV, IX, XL, XC, CD, CM).

^(?=[MDCLXVI])M{0,3}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$

HardNumbers

Scientific Notation Regex

Validates a number written in scientific (exponential) notation, such as 1.23e-10 or -6.022E23, with a mantissa, an e/E marker, and a signed integer exponent.

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

HardProgramming

Semantic Version (SemVer) Regex

Validates a full Semantic Versioning 2.0.0 string, including major.minor.patch, optional prerelease identifiers, and optional build metadata, matching the official semver.org grammar.

^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$

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

snake_case Identifier Regex

Validates that a string is a lower_snake_case identifier: lowercase words separated by single underscores, with no leading, trailing, or doubled underscores.

MediumProgramming

Validates a SQL identifier (table or column name) in any of its common forms: a plain unquoted identifier, a double-quoted identifier (ANSI SQL/PostgreSQL), a backtick-quoted identifier (MySQL), or a bracket-quoted identifier (SQL Server).

^(?:[A-Za-z_][A-Za-z0-9_]*|"[^"]*"|`[^`]*`|\[[^\]]*\])$

HardSecurity

Strong Password Regex

Validates that a password is at least 8 characters long and contains a lowercase letter, an uppercase letter, a digit, and a special character, using lookahead assertions.

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[!@#$%^&*])[A-Za-z\d!@#$%^&*]{8,}$

MediumNetworking

Subdomain Regex

Validates a hostname that includes at least one subdomain label in front of a base domain and top-level domain, such as www.example.com or api.staging.example.co.uk.

^([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.){2,}[a-zA-Z]{2,}$

^(6553[0-5]|655[0-2]\d|65[0-4]\d\d|6[0-4]\d{3}|[1-5]\d{4}|[1-9]\d{0,3}|0)$

Tab Character Regex

Matches one or more consecutive tab characters, useful for detecting or converting tab-indented text.

\t+

HardNetworking

TCP/UDP Port Number Regex

Validates that a string is a valid TCP or UDP port number in the full range 0 to 65535, rejecting values outside that range and leading zeros.

^-?\d+(\.\d+)?\s?°?[CFK]$

Temperature Regex

Validates a temperature value made of a signed number, an optional space and degree symbol, and a unit letter for Celsius, Fahrenheit, or Kelvin.

^https?:\/\/(?:www\.)?(?:twitter|x)\.com\/(\w{1,15})(?:\/status\/(\d+))?\/?$

Twitter/X URL Regex

Matches a Twitter/X profile URL or an individual tweet (status) URL on either twitter.com or x.com, capturing the handle and optional tweet ID.

^(GIR 0AA|((([A-Z][0-9]{1,2})|([A-Z][A-HJ-Y][0-9]{1,2})|([A-Z][0-9][A-Z])|([A-Z][A-HJ-Y][0-9][A-Z]?))\s?[0-9][A-Z]{2}))$

UK Postcode Regex

Validates a United Kingdom postcode across all standard outward-code formats (area + district) plus the fixed-format inward code, including the special GIR 0AA Girobank postcode.

HardText Processing

Unicode Escape Sequence Regex

Matches JavaScript-style Unicode escape sequences, both the fixed 4-hex-digit form \uXXXX and the code-point brace form \u{XXXXX}.

\\u(?:[0-9A-Fa-f]{4}|\{[0-9A-Fa-f]{1,6}\})

EasyFiles

Unix File Path Regex

Validates an absolute Unix-style file path such as /home/user/file.txt, rejecting relative paths and double slashes.

^/(?:[^/]+/?)*$

EasyDates

Unix Timestamp Regex

Matches a numeric Unix epoch timestamp in either 10-digit seconds precision or 13-digit millisecond precision.

^\d{10}(\d{3})?$

[A-Za-z0-9_.~%+-]+=[A-Za-z0-9_.~%+-]*

URL Query Parameter Regex

Matches a single key=value pair within a URL query string, where both the key and the (optionally empty) value contain only URL-safe characters.

^https?:\/\/[\w-]+(\.[\w-]+)+(:\d+)?([\/?#][^\s]*)?$

URL Regex

Validates HTTP and HTTPS URLs with a required host containing at least one dot, an optional port, and an optional path, query, or fragment.

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

URL Slug Regex

Validates a URL-friendly slug made of lowercase letters and digits, with single hyphens allowed only between word groups (no leading, trailing, or doubled hyphens).

^https?:\/\/[a-zA-Z0-9.-]+:\d{2,5}(\/[^\s]*)?$

URL with Port Regex

Validates an HTTP or HTTPS URL that explicitly includes a port number after the hostname, with an optional path, query string, or fragment.

MediumDates

US Date Regex (MM/DD/YYYY)

Validates a calendar date in the US MM/DD/YYYY format with slash separators, requiring zero-padded month and day values.

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

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

US Dollar Currency Regex

Validates a US dollar amount with a leading dollar sign, comma-grouped thousands, and an optional two-digit cents portion, such as $1,234.56.

^(?!000|666|9\d{2})\d{3}-(?!00)\d{2}-(?!0000)\d{4}$

US Social Security Number Regex

Validates the format of a US Social Security Number (123-45-6789), rejecting area, group, and serial values that the SSA never issues, such as area 000, 666, or 900-999.

US ZIP Code Regex

Validates United States ZIP codes in both the standard 5-digit form and the extended ZIP+4 form (e.g. 12345-6789).

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

EasyValidation

Username Regex

Validates that a username is 3 to 16 characters long and contains only letters, digits, underscores, or hyphens.

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

^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$

UUID Regex

Validates a standard 8-4-4-4-12 hyphenated UUID string, including the version nibble and RFC 4122 variant bits.