Is Konnect2Tools free?

Yes. These in-browser tools are completely free to use with no account required for core functionality.

Do my files leave my device?

Browser document operations run locally, except where the operation uses an external service, such as AI summarisation. Read the processing note before using sensitive inputs.

Is the Regex Tester tool safe to use?

Local operations process document content on your device. External-service operations may send inputs as described in the processing note. Keep originals and inspect the output.

What does the g flag do in regex?

The g (global) flag makes the regex find all matches instead of stopping at the first one. Without g, regex.exec() and string.match() return only the first match. With g, matchAll() returns all matches. The g flag is essential for replace-all operations with string.replace().

What is the difference between . and [\s\S] in regex?

The . metacharacter matches any character EXCEPT newlines. To match any character including newlines, use [\s\S] (whitespace OR non-whitespace — covers everything) or use the s (dotAll) flag which makes . match newlines too.

How do I validate an Indian mobile number with regex?

Pattern: /^[6-9]\d{9}$/ — starts with 6, 7, 8, or 9 (valid Indian mobile number first digits), followed by exactly 9 more digits. With country code: /^(\+91|0)?[6-9]\d{9}$/. This validates 10-digit mobile numbers with optional +91 or 0 prefix.

What is a capture group in regex?

Capture groups are created with parentheses ( ) and extract matched substrings. For example, /(\d{4})-(\d{2})-(\d{2})/ matches a date and captures year, month, day separately in groups 1, 2, 3. Named groups (? \d{4}) make the result more readable as match.groups.year.

Developer & data utilities

Regex Tester

Test regular expressions against input strings with match highlighting and group capture.

Run Regex Tester online

In-browserDocument processing runs on your device. External resources may still load.

Enable JavaScript to use the interactive tool. Read the instructions, limitations and FAQs below before starting.

The Regex Tester lets you write and test JavaScript regular expressions against any input string with live match highlighting. Regular expressions are patterns used to match, search, and manipulate text — a critical skill for every developer, data analyst, and system administrator.

Our tool shows all matches, their positions, and capture groups in real time. JavaScript regex supports flags: g (global — find all matches), i (case insensitive), m (multiline — ^ and $ match line boundaries), and s (dotAll — . matches newlines). Understanding flags dramatically expands regex capabilities.

Common regex use cases: validating email addresses, phone numbers, and PAN/Aadhaar formats; extracting data from log files; find-and-replace in code editors; building URL routing patterns; sanitizing user input; and parsing structured text like dates and prices.

How to use this utility

Use the controls below—paste text, pick files, or adjust options as described on the tool.
Click the main action button. Processing runs in your browser on this device.
Download or copy the output. Check the processing note for any external services used by this operation.

Common use cases

Validating Indian phone numbers, PAN, and Aadhaar format in forms
Extracting data from structured log files using capture groups
Building URL routing patterns for Express or Django
Finding and replacing patterns in bulk text processing scripts
Testing regex before adding to production code validators

Tips for best results

1Use https://regex101.com for detailed explanation of each regex token
2Anchor with ^ and $ to match the whole string, not just a substring
3Use non-capturing groups (?:) when you don't need to extract the group value
4Lazy quantifiers (*?) are safer than greedy (*) to avoid over-matching
5Test with both valid and invalid inputs — edge cases reveal regex weaknesses

Frequently asked questions

Is Konnect2Tools free?: Yes. These in-browser tools are completely free to use with no account required for core functionality.
Do my files leave my device?: Browser document operations run locally, except where the operation uses an external service, such as AI summarisation. Read the processing note before using sensitive inputs.
Is the Regex Tester tool safe to use?: Local operations process document content on your device. External-service operations may send inputs as described in the processing note. Keep originals and inspect the output.
What does the g flag do in regex?: The g (global) flag makes the regex find all matches instead of stopping at the first one. Without g, regex.exec() and string.match() return only the first match. With g, matchAll() returns all matches. The g flag is essential for replace-all operations with string.replace().
What is the difference between . and [\s\S] in regex?: The . metacharacter matches any character EXCEPT newlines. To match any character including newlines, use [\s\S] (whitespace OR non-whitespace — covers everything) or use the s (dotAll) flag which makes . match newlines too.
How do I validate an Indian mobile number with regex?: Pattern: /^[6-9]\d{9}$/ — starts with 6, 7, 8, or 9 (valid Indian mobile number first digits), followed by exactly 9 more digits. With country code: /^(\+91|0)?[6-9]\d{9}$/. This validates 10-digit mobile numbers with optional +91 or 0 prefix.
What is a capture group in regex?: Capture groups are created with parentheses ( ) and extract matched substrings. For example, /(\d{4})-(\d{2})-(\d{2})/ matches a date and captures year, month, day separately in groups 1, 2, 3. Named groups (?<year>\d{4}) make the result more readable as match.groups.year.

Continue with another utility in developer & data utilities.

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