About Date Regex Tester
This page opens with a pattern for ISO dates that names its three parts, year, month and day, and it already holds a replacement that rewrites each date as day/month/year. It is free, needs no sign-up and runs in your browser, so nothing you enter is uploaded.
The text becomes: Start 14/03/2026, end 02/10/2026. Invalid month: 2026-13-01. Invalid day: 2026-02-45.
The pattern limits months to 01 to 12 and days to 01 to 31, so "2026-13-01" is rejected. It does not know that February has no 30th, so a date such as 2026-02-30 still matches. Use a date library when you need real calendar validation.
How to use Date Regex Tester
- Type or paste a regular expression into the pattern field, or pick one from the Try chips: email, URL, phone, date, IPv4 or hex colour.
- Toggle the flags you need: g for all matches, i to ignore case, m for multiline, s so the dot matches line breaks, u for Unicode and y for sticky.
- Paste your test text. Matches are highlighted as you type.
- Read the table under the tester for each match, its position, and its numbered and named groups.
- Switch to Replace to try a replacement string. Use $1, $2 and $<name> to reuse groups, then copy the result.
- Read "What the pattern means" to check the pattern does what you think.
Features
- JavaScript regex flavour with flags g, i, m, s, u and y.
- Live highlighted matches, with alternating colours so neighbouring matches stay distinct.
- Numbered and named capture groups in a table.
- Replace mode with $1, $<name> and $& in the replacement.
- A plain-English explanation of every token, with groups indented.
- A small pattern library with real test strings.
- Catastrophic backtracking protection: matching runs in a Web Worker and is stopped after a short time limit.
- Clear error messages for an invalid pattern.
Worked examples
\b(?<year>\d{4})-(?<month>0[1-9]|1[0-2])-(?<day>0[1-9]|[12]\d|3[01])\b gives 2026-03-14, 2026-10-02
Named groups make the replacement $<day>/$<month>/$<year> easy to read.
Privacy: how it works
- The pattern and the text are processed by code in this browser tab. Nothing is sent to Ulkaa or to any other server.
Tips
- Escape the special characters . * + ? ( ) [ ] { } ^ $ | \ with a backslash when you mean them literally.
- Prefer specific classes over the dot: [^"]* is faster and safer than .* when matching up to a quote.
- Anchor a validation pattern with ^ and $, or it will match a valid piece inside invalid text.
- Turn on the m flag when your text has several lines and you want ^ and $ per line.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Your pattern and text are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Your pattern and text are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
Why use named groups for dates?
They document the pattern and let a replacement refer to $<year>, $<month> and $<day> instead of counting parentheses.
More Regex Tester pages
- Regex TesterType a pattern and some text, and see every match, group and replacement as you type.
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- URL Regex TesterFind web addresses in a block of text with a pattern you can edit.
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- IPv4 Address Regex TesterMatch four numbers from 0 to 255 separated by dots.
- Hex Color Regex TesterFind #rgb and #rrggbb colours in a stylesheet or text.
- Password Strength RegexSee which sample passwords pass a rule built from lookaheads.
- Remove Extra Spaces With RegexReplace runs of whitespace with a single space.
- Extract Numbers With RegexPull every number, including decimals and negatives, out of text.
- Regex Replace With Capture GroupsReorder words with $1 and $2 in the replacement.
- Regex Named Groups TesterCapture the level, service and message of a log line by name.