Question 1

Is regexhome free to use?

Accepted Answer

Yes. regexhome is 100% free and requires no account, subscription, credit card, or payment. Open the workbench and start testing patterns straight away.

Question 2

Do I need to sign up or create an account?

Accepted Answer

No. regexhome has zero accounts, logins, or registration forms. Everything runs in your local browser session without any authentication barrier or paywalls.

Question 3

Is my test text uploaded to a server?

Accepted Answer

Never. Regex evaluation, match parsing, and replacement are executed 100% locally in your web browser via client-side JavaScript. No text, patterns, API tokens, or test suites are ever sent to our servers.

Question 4

Where are my saved patterns stored?

Accepted Answer

Saved patterns and custom test suites are stored strictly in your browser's local storage (localStorage). You can back up, transfer, or restore them anytime using the JSON export/import buttons in the sidebar.

Question 5

Can I use regexhome offline?

Accepted Answer

Yes. Once the page assets are cached by your browser, the tester, visual builder, explainer, and step debugger function completely offline without any internet connection.

Question 6

Which browsers are supported?

Accepted Answer

regexhome supports all modern desktop and mobile browsers, including Google Chrome, Microsoft Edge, Mozilla Firefox, Apple Safari, Opera, and Chromium-based browsers with ECMAScript RegExp engine compliance.

Question 7

How do replace tokens work ($$, $1, $2, $<name>)?

Accepted Answer

In the Replace tab, use $$ or $& to insert the entire matched substring, $1 through $9 to insert indexed capture groups, and $<name> for named capture groups. You can also use $` and $' to reference text before and after the match.

Question 8

How does the step debugger measure performance?

Accepted Answer

The step debugger calculates execution duration, backtrack operations, recursion depth, and detects high-risk patterns (such as nested quantifiers or catastrophic backtracking risks) to keep your web apps fast and secure.

Question 9

Can I write automated regression test cases?

Accepted Answer

Yes! The Tests tab lets you specify unit test strings with pass/fail criteria (e.g., must match at least N times, must not match, must capture exact substrings). Tests automatically re-evaluate whenever you modify your pattern.

Question 10

How do I load a built-in snippet into the tester?

Accepted Answer

In the Pattern Library sidebar, browse pre-built snippets by category (e.g., email, URL, IPv4, phone, date, slug) and click "+ Use" to instantly load the pattern, flags, and sample text into the active workbench.

Question 11

What is regex?

Accepted Answer

Regex (short for Regular Expression, also known as regexp or rational expression) is a sequence of characters that forms a search pattern. It is widely used in software development, text editors, databases, and scripting to search, extract, parse, and validate strings according to formal rules.

Question 12

What is a regex pattern?

Accepted Answer

A regex pattern is a template or formula composed of literal characters and metacharacters (such as \d, ^, $, *, +) that dictates how a regular expression engine matches substrings within target text. For example, \d{4} is a pattern that matches four consecutive digit characters.

Question 13

What is regex used for?

Accepted Answer

Regex is used for form input validation (emails, phone numbers, passwords), data extraction (web scraping, extracting IDs or logs), string search-and-replace (code refactoring, date reformatting), lexical parsing, and server log analysis across all major programming languages including JavaScript, Python, Java, Go, and PHP.

Question 14

What is a RegEx rule?

Accepted Answer

A RegEx rule is a formal pattern specification that defines what characters, sequences, lengths, and structures are permitted or prohibited in a given text string. Rules enforce constraints like requiring an uppercase letter, enforcing minimum length, or disallowing special symbols.

Question 15

How can I learn regex?

Accepted Answer

The most effective way to learn regex is through interactive practice: 1) Master basic literal characters and common classes (\d for digits, \w for words, \s for whitespace); 2) Learn anchors (^ for start, $ for end, \b for word boundary); 3) Practice quantifiers (*, +, ?, {n,m}); 4) Use RegexHome’s visual pattern builder and plain-English explainer to break down patterns step-by-step.

Question 16

What is the best regex tester and maker tool?

Accepted Answer

RegexHome is one of the best online regex tester and maker tools. It runs 100% locally in your browser with zero latency, provides instant match highlighting, an interactive visual pattern builder, plain-English explanations, and a step-by-step backtracking debugger without ever uploading your private text to a server.

Question 17

What is the best online regex validator?

Accepted Answer

RegexHome is a premier online regex validator. It executes real-time JavaScript ECMAScript RegExp parsing, validates syntax immediately on every keystroke, highlights invalid tokens with actionable explanations, and includes an integrated test assertion suite to prevent regressions.

Question 18

How can I test my regex code?

Accepted Answer

You can test your regex code by entering your pattern and flags into RegexHome and pasting your target text into the editor. Matches, capture groups, and replacement previews update immediately. You can also add automated test cases in the "Tests" tab to verify pass/fail criteria across multiple edge cases.

Question 19

How to check if regex is valid?

Accepted Answer

To check if a regex is valid, enter it into RegexHome; our parser immediately detects syntax errors (such as unclosed groups, invalid ranges, or trailing backslashes) and provides plain-English error messages. Programmatically in JavaScript, you can validate a pattern by instantiating new RegExp(pattern) inside a try...catch block.

Question 20

How can I check a regular expression online?

Accepted Answer

Visit RegexHome, type your regular expression in the pattern input, choose your flags (e.g. g, i, m, s, u), and supply sample text. The online engine evaluates the pattern in real time, highlighting matches, capturing groups, index offsets, and substitution outputs instantly.

Question 21

What is regex validation?

Accepted Answer

Regex validation is the process of testing whether an input string completely conforms to an expected format (such as an email address, credit card number, postal code, or UUID) before accepting it in an application or storing it in a database.

Question 22

What do the regex flags (g, i, m, s, u, y) do?

Accepted Answer

g (global) matches all occurrences; i makes matching case-insensitive; m allows ^ and $ to match start/end of individual lines; s (dotAll) allows . to match newline characters; u enables full Unicode code point support; y enables sticky index matching.

Question 23

What is the difference between greedy and lazy quantifiers?

Accepted Answer

Greedy quantifiers (*, +, {n,m}) consume as many characters as possible before attempting subsequent tokens. Appending a question mark (*?, +?, {n,m}?) turns them into lazy (non-greedy) quantifiers, matching the smallest possible substring.

Question 24

How do positive and negative lookarounds work?

Accepted Answer

Positive lookahead (?=...) checks that a sub-pattern follows without consuming characters; negative lookahead (?!...) asserts that a sub-pattern must not follow. Similarly, positive lookbehind (?<=...) and negative lookbehind (?<!...) check characters preceding the match.

Question 25

How do I match a string with a regex pattern?

Accepted Answer

In JavaScript, you can match a string using RegExp.prototype.test() for boolean validation (e.g. /pattern/.test(str)), String.prototype.match() or matchAll() to retrieve matches and capture groups, or String.prototype.search() to find the match position.

Question 26

How to do regex matching?

Accepted Answer

Regex matching is performed by passing a target string to a regular expression engine. The engine processes the string character by character, testing each token, advancing on successful matches, and backtracking when a path fails until all match positions are identified.

Question 27

What regex can I use to match everything?

Accepted Answer

To match any character including newlines across the entire text, use the character class [\s\S]* or [\d\D]*. Alternatively, in modern JavaScript engines, you can use .* combined with the dotAll flag (/.* /s).

Question 28

What does the RegEx \s*,\s* do?

Accepted Answer

The regex \s*,\s* matches a comma surrounded by zero or more whitespace characters on either side (spaces, tabs, newlines). It is commonly used to split or clean comma-separated lists (e.g. "apple , banana , orange") into trimmed values.

Question 29

What does $1 mean in RegEx?

Accepted Answer

In regex replacement and string substitution operations, $1 refers to the content captured by the first capturing group (...) in the pattern. For example, replacing /(\w+)\s(\w+)/ with "$2, $1" transforms "John Doe" into "Doe, John".

Question 30

What does a caret (^) mean in RegEx?

Accepted Answer

The caret symbol (^) has two distinct meanings in regex: 1) Position Anchor: When placed at the start of a pattern (e.g. ^abc), it asserts that the match must occur at the beginning of the string or line; 2) Negated Character Set: When placed at the start of a character bracket (e.g. [^0-9]), it negates the set, matching any character that is NOT a digit.

Question 31

How to build a regex pattern?

Accepted Answer

To build a regex pattern: 1) Identify required character sets (e.g. [a-zA-Z], \d); 2) Anchor boundaries with ^, $, or \b; 3) Add quantifiers (+, *, {n,m}) to specify frequency; 4) Group logical units using parentheses (...); 5) Test and iterate against positive and negative sample cases in RegexHome.

Question 32

What are some common regex patterns?

Accepted Answer

Popular regular expressions include: Email validation (^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$), URL matching (https?:\/\/[^\s/$.?#].[^\s]*), Digits only (^\d+$), Alphanumeric username (^[a-zA-Z0-9_]{3,16}$), and Date in YYYY-MM-DD format (^\d{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[12]\d|3[01])$).

Question 33

How can I use regex to check if an email is valid?

Accepted Answer

You can validate email addresses using the RFC 5322 standard pattern: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$. This verifies that the username contains valid characters, an @ symbol is present, followed by a valid domain and a top-level domain of at least two characters.

Question 34

How can I use regex to validate phone numbers?

Accepted Answer

To validate international and standard phone numbers with optional country codes, brackets, dots, or hyphens, use: ^\+?[1-9]\d{0,2}[-.\s]?$?\d{1,4}$?[-.\s]?\d{1,4}[-.\s]?\d{1,9}$. For standard 10-digit North American numbers, use: ^(?:\+1[-.\s]?)?$?([0-9]{3})$?[-.\s]?([0-9]{3})[-.\s]?([0-9]{4})$.

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