Regular Expression Checker
Check and validate PHP, JavaScript, and Python regular expressions
Features
Match as you type
Reflect the result in response to the pattern and text input
Highlight matched parts
Visually emphasize matched strings in a table with line numbers
Supports i, g, m, s, and u modifiers
Freely combine flags such as case-insensitivity and multiline
Try instantly with built-in samples
Call up prepared pattern and text examples with a button
How to Use
Enter the regular expression pattern
Write the pattern you want to match in the upper input field
Enter the text to validate
Paste the text you want to match in the lower text area
Select flags as needed
Specify modifiers with the i, g, m, s, and u checkboxes
Check the result with the check
Show the match results with matched parts highlighted on the spot
Use Cases
Debugging patterns
Isolate the cause of a regular expression that does not match as intended
Designing input validation
Test validation patterns for email or phone numbers before implementation
Checking information extraction from logs
Validate extracting the target strings from logs and text
Learning and practicing regular expressions
Master the behavior of flags and metacharacters by trying real examples
Basic Knowledge
What is Regular Expression?
A regular expression is a notation that uses symbols to represent character patterns such as "3 digits" or "strings containing @", and is widely used for search, replacement, and input validation. For example, \d{3} matches exactly 3 digits.
Main Modifiers (Flags)
- i, g：i means case-insensitive matching, and g means find all matches instead of stopping at the first one. This is the most commonly used combination.
- m (Multiline)：m is multiline mode, where ^ and $ match the beginning and end of each line, respectively, rather than the entire text.
- s, u：s means dot (.) matches newline characters as well, and u is Unicode mode, which correctly handles surrogate pair characters (certain kanji and emoji) on a code point basis.
Safety and Privacy
Runs entirely in your browser
Your input data is processed only within your browser and is never sent externally.
Processing only in your browser
matching the regular expression is processed entirely within your browser, and input data is not sent to any server.
Communications encrypted with HTTPS
Page loading is also encrypted by TLS, and content cannot be read by third parties.
No transmission to third parties
Input content is not sent to external services such as ad networks or trackers.
No automatic saving of results
the pattern and text and input suggestions are not stored on the server.
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RAKKOTOOLS is free to use!
Available free of charge for individuals and corporations, commercial and non-commercial use alike.No prior permission or usage application is required. Feel free to use it in various situations.
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Use in schools, work, and events
Can be used in various situations such as classes, team division, internal work, and events.
Introduction on Web, books, and SNS
Feel free to introduce it as a useful tool on web media, books, SNS, and other platforms.
Commercial use
Can be used for commercial purposes such as research, calculation, processing, and conversion in business and production.
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If using in streaming and videos
Link to RAKKOTOOLS in the description, or Mention or display that you are using RAKKOTOOLS in the stream or video.
Credit example for the description
Usage guidelinesYou are free to use it for normal purposes. However, use for purposes that violate laws, infringe on third-party rights, impose significant load on the service, or otherwise interfere with service operation is prohibited.
We do not guarantee the accuracy or completeness of information and calculation results obtained from each tool.
This notice is a translation of the original Japanese text. If there is any discrepancy between the translation and the original, the Japanese original takes precedence.