Can I use capture groups and backreferences?

Yes. You can use parentheses to create capture groups, and the match details panel will show each group's captured value. Named capture groups using the (? ...) syntax are also supported. Backreferences such as \1 or \k can be used within the pattern for matching repeated content.

Penguji Regex

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Regular expressions (regex or regexp) are powerful patterns used to search, match, and manipulate text. They are supported in virtually every programming language and are essential for tasks like input validation, data extraction, log parsing, and text replacement. However, regex syntax can be complex and difficult to debug without the right tools. Our free online regex tester provides a live testing environment where you can write a regex pattern and immediately see all matches highlighted in your test string. It supports JavaScript regex syntax, displays captured groups, shows match details with positions, and includes a comprehensive cheat sheet covering all common patterns, anchors, quantifiers, and flags.

Cara Penggunaan

Enter your regular expression pattern in the regex input field. You can include flags such as g (global), i (case-insensitive), m (multiline), and s (dotAll) by appending them after the closing delimiter.
Type or paste your test string into the text area below. All regex matches will be highlighted in real time as you type, with different colors for each capture group.
Review the match details panel, which shows each match's position, length, and captured group values. This helps you verify that your pattern captures exactly what you intend.
Use the built-in cheat sheet as a quick reference for regex syntax. Click any pattern in the cheat sheet to insert it into your regex, and experiment with different combinations.
Iterate on your pattern until all matches are correct. Copy the final regex pattern to use in your JavaScript, Python, Java, or any other language that supports regular expressions.

Pertanyaan yang Sering Diajukan

A regex tester is an online tool that helps you write, test, and debug regular expressions in real-time. You can enter a regex pattern and test string to instantly see matches, captured groups, and any errors. It's essential for developers working with text parsing, form validation, data extraction, or log analysis. Our regex tester supports JavaScript syntax and provides 50+ ready-to-use patterns for common tasks like email validation, phone number matching, and URL extraction.

Testing regex online is simple: 1) Enter your regex pattern in the pattern field (e.g., ^\w+@\w+\.\w+$ for basic email). 2) Type or paste your test string in the text area. 3) See matches highlighted instantly with details showing position and captured groups. 4) Toggle flags like 'g' (global) or 'i' (case-insensitive) to refine your search. 5) Use our 50+ built-in patterns as starting points for common validation tasks.

Regex flags modify how patterns match: g (global) finds all matches instead of just the first; i (case-insensitive) ignores uppercase/lowercase differences; m (multiline) makes ^ and $ match line starts/ends; s (dotAll) lets . match newlines; u (Unicode) enables full Unicode support. In our tester, click the flag buttons to toggle them on/off. Combine multiple flags like 'gi' for case-insensitive global matching. Flags are appended after the closing slash in JavaScript regex notation.

For basic email validation, use: ^[\w.-]+@[\w.-]+\.\w{2,}$. This matches: one or more word characters/dots/hyphens, followed by @, then more word characters/dots/hyphens, a dot, and 2+ letters for the domain. For stricter validation (RFC-compliant), use: ^(?:(?:[^<>()[\]\\.,;:\s@\"]+(?:\.[^<>()[\]\\.,;:\s@\"]+)*)|(?:\".+"))@(?:(?:\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(?:(?:[a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$. Test with various valid and invalid emails to ensure accuracy.

Greedy quantifiers (*, +, {n,}) match as much as possible while still allowing the overall pattern to succeed. Lazy quantifiers (*?, +?, {n,}?) match as little as possible. Example: For text 'abc123def', the greedy pattern .+ matches the entire string, while the lazy pattern .+? matches only 'a'. Use greedy matching when you want the longest possible match, and lazy matching when you need the shortest match, such as matching HTML tags or quoted strings.

JavaScript: Use /pattern/flags or new RegExp('pattern', 'flags'). Methods: .test(), .exec(), .match(), .replace(), .split(). Python: Import re module. Use re.search(), re.match(), re.findall(), re.sub(). Pattern as string with r'raw' notation. Java: Use Pattern.compile('pattern') to create a Pattern object, then matcher(input) to get a Matcher. Methods: .find(), .matches(), .replaceAll(), .split(). Most features are portable, but syntax for flags and special features varies slightly between languages.

This tool uses JavaScript's RegExp engine, which supports most common regex features including character classes, quantifiers, lookaheads, lookbehinds, backreferences, named capture groups, and Unicode property escapes. While most patterns are portable across languages, some advanced features may differ between regex engines (e.g., Python's re module, PCRE, or .NET regex).

Yes. You can use parentheses to create capture groups, and the match details panel will show each group's captured value. Named capture groups using the (?<name>...) syntax are also supported. Backreferences such as \1 or \k<name> can be used within the pattern for matching repeated content.

Contoh

Regex to Validate Email Address

Matches standard email formats. Use for: form validation, user registration, data cleaning.

^[\w.-]+@[\w.-]+\.\w{2,}$

Regex for Phone Number (US)

Matches US phone numbers in various formats. Use for: contact forms, CRM data validation.

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

Regex for URL Validation

Matches HTTP and HTTPS URLs. Use for: link validation, content scraping, SEO analysis.

https?:\/\/[\w.-]+(?:\.[\w.-]+)+[\w\-._~:/?#[\]@!$&'()*+,;=]*$

Regex for IP Address (IPv4)

Matches valid IPv4 addresses. Use for: network configuration, log analysis, access control.

^(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d\d?)$

Regex for Date Format (YYYY-MM-DD)

Matches dates in ISO format. Use for: data validation, date parsing, log filtering.

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

Regex for Password Strength

Requires 8+ chars, uppercase, lowercase, number. Use for: registration forms, security policies.

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

Regex for Chinese Characters

Matches Chinese Unicode characters. Use for: multilingual content validation, NLP processing.

[\u4e00-\u9fff]+

Regex for Numbers Only

Matches integers and decimals. Use for: numeric input validation, data extraction.

^\d+(?:\.\d+)?$

Regex to Remove HTML Tags

Matches HTML tags for removal. Use for: content cleaning, text extraction, sanitization.

<[^>]+>

Regex for Credit Card Number

Matches common credit card formats (Visa, MC). Use for: payment form validation.

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

Extract Email Addresses

Finds all emails in text. Use for: lead generation, contact harvesting, data mining.

[\w.-]+@[\w.-]+\.\w{2,}

Extract URLs from Text

Finds HTTP/HTTPS links. Use for: link analysis, content scraping, SEO auditing.

https?:\/\/[\w.-]+(?:\.[\w.-]+)+[\w\-._~:/?#[\]@!$&'()*+,;=]*

Extract Hashtags

Finds Twitter/social media hashtags. Use for: social media analysis, trend monitoring.

#[a-zA-Z0-9_]+

Extract JSON Values

Matches quoted string values in JSON. Use for: JSON parsing, data extraction.

"(?:[^"\\]|\\.)*"

Extract Domain from URL

Extracts domain name. Use for: link analysis, domain filtering, analytics.

https?:\/\/(?:www\.)?([\w.-]+)

Replace Multiple Spaces with One

Normalizes whitespace. Use for: text formatting, data cleaning, display purposes.

\s+

Remove Non-Alphanumeric Characters

Keeps only letters and numbers. Use for: slug generation, username validation, sanitization.

[^a-zA-Z0-9]

Validate Hex Color Code

Matches #RGB or #RRGGBB. Use for: color input validation, CSS parsing.

^#(?:[0-9a-fA-F]{3}){1,2}$

Regex for Username

Alphanumeric, 3-16 chars. Use for: registration validation, user management.

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

Match Empty Lines

Finds blank lines. Use for: text formatting, paragraph detection, document cleaning.

^\s*$

Regex for Slug/URL-friendly String

Lowercase, hyphens only. Use for: URL generation, SEO-friendly identifiers.

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

Extract Time (HH:MM or HH:MM:SS)

Matches time formats. Use for: log parsing, schedule extraction, data validation.

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

Alat Terkait

Pemformat JSON

Percantik, validasi, dan minifikasi data JSON

Enkode / Dekode URL

Enkode atau dekode URL dan parameter kueri

Pemeriksa Perbedaan Teks

Bandingkan dua teks dan soroti perbedaannya

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Cara Penggunaan

Enter your regular expression pattern in the regex input field. You can include flags such as g (global), i (case-insensitive), m (multiline), and s (dotAll) by appending them after the closing delimiter.

Type or paste your test string into the text area below. All regex matches will be highlighted in real time as you type, with different colors for each capture group.

Review the match details panel, which shows each match's position, length, and captured group values. This helps you verify that your pattern captures exactly what you intend.

Use the built-in cheat sheet as a quick reference for regex syntax. Click any pattern in the cheat sheet to insert it into your regex, and experiment with different combinations.

Iterate on your pattern until all matches are correct. Copy the final regex pattern to use in your JavaScript, Python, Java, or any other language that supports regular expressions.

Pertanyaan yang Sering Diajukan

Contoh

Regex to Validate Email Address

Matches standard email formats. Use for: form validation, user registration, data cleaning.

^[\w.-]+@[\w.-]+\.\w{2,}$

Regex for Phone Number (US)

Matches US phone numbers in various formats. Use for: contact forms, CRM data validation.

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

Regex for URL Validation

Matches HTTP and HTTPS URLs. Use for: link validation, content scraping, SEO analysis.

https?:\/\/[\w.-]+(?:\.[\w.-]+)+[\w\-._~:/?#[\]@!$&'()*+,;=]*$

Regex for IP Address (IPv4)

Matches valid IPv4 addresses. Use for: network configuration, log analysis, access control.

^(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d\d?)$

Regex for Date Format (YYYY-MM-DD)

Matches dates in ISO format. Use for: data validation, date parsing, log filtering.

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

Regex for Password Strength

Requires 8+ chars, uppercase, lowercase, number. Use for: registration forms, security policies.

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

Regex for Chinese Characters

Matches Chinese Unicode characters. Use for: multilingual content validation, NLP processing.

[\u4e00-\u9fff]+

Regex for Numbers Only

Matches integers and decimals. Use for: numeric input validation, data extraction.

^\d+(?:\.\d+)?$

Regex to Remove HTML Tags

Matches HTML tags for removal. Use for: content cleaning, text extraction, sanitization.

<[^>]+>

Regex for Credit Card Number

Matches common credit card formats (Visa, MC). Use for: payment form validation.

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

Extract Email Addresses

Finds all emails in text. Use for: lead generation, contact harvesting, data mining.

[\w.-]+@[\w.-]+\.\w{2,}

Extract URLs from Text

Finds HTTP/HTTPS links. Use for: link analysis, content scraping, SEO auditing.

https?:\/\/[\w.-]+(?:\.[\w.-]+)+[\w\-._~:/?#[\]@!$&'()*+,;=]*

Extract Hashtags

Finds Twitter/social media hashtags. Use for: social media analysis, trend monitoring.

#[a-zA-Z0-9_]+

Extract JSON Values

Matches quoted string values in JSON. Use for: JSON parsing, data extraction.

"(?:[^"\\]|\\.)*"

Extract Domain from URL

Extracts domain name. Use for: link analysis, domain filtering, analytics.

https?:\/\/(?:www\.)?([\w.-]+)

Replace Multiple Spaces with One

Normalizes whitespace. Use for: text formatting, data cleaning, display purposes.

\s+

Remove Non-Alphanumeric Characters

Keeps only letters and numbers. Use for: slug generation, username validation, sanitization.

[^a-zA-Z0-9]

Validate Hex Color Code

Matches #RGB or #RRGGBB. Use for: color input validation, CSS parsing.

^#(?:[0-9a-fA-F]{3}){1,2}$

Regex for Username

Alphanumeric, 3-16 chars. Use for: registration validation, user management.

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

Match Empty Lines

Finds blank lines. Use for: text formatting, paragraph detection, document cleaning.

^\s*$

Regex for Slug/URL-friendly String

Lowercase, hyphens only. Use for: URL generation, SEO-friendly identifiers.

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

Extract Time (HH:MM or HH:MM:SS)

Matches time formats. Use for: log parsing, schedule extraction, data validation.

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