Regular expression helper
Start a regular expression from a template for literal text, integers, hex values, dates or emails, then edit it to fit.
- Runs in your browser
- No upload
- Result stays on your device
Privacy & limitsRuns in your browser. Nothing is uploaded.
Input content stays in this tab; Refentra does not upload or store it. Optional aggregate action counts are sent only with your usage consent. Clear the workspace when finished.
Supported profile: Editable shape templates; date/email patterns do not prove validity.
Maximum text: 200,000 UTF-16 units; parser limits can be smaller. Worker time limit: 15 seconds (regex 1.5 seconds).
Check the input and the result
- Prepare and choose the operation
Choose a literal, integer, hexadecimal, date or email template. Only literal mode escapes the text you supply.
- Check a concrete example
Use this sample and compare the indicated result: a+b → literal → a\+b; a+b ✓, aaab ✗
- Check the output before you reuse it
In the regex tester, try both matching examples and deliberately invalid ones. Check the anchors before you embed the pattern.
Answers for this task
Does the date template validate a calendar?
It only checks the shape of the text. A string that looks like a date can still contain an impossible day or month.
What should I check if the input fails?
Escape the syntax again only when you embed the pattern in a programming-language string. Regex text and string literals have different layers of escaping.
Where does this tool stop?
Templates are starting points. They don't verify a mailbox, they aren't a full email RFC implementation, and they can't build a regex from a description in everyday language.