Regex Builder & Tester for GA4

How to use the regex builder for GA4

This regex builder for GA4 writes and checks patterns with the rules GA4 really uses, from Google's regular expressions help page: RE2 syntax, a full match by default, and case sensitivity that changes from place to place. A generic online tester checks none of that, which is why a pattern can pass there and still fail in your report.

1. Choose where the regex goes. Pick the report filter match type, exploration, audience, channel group, event rule or internal traffic rule. The checks change with it.
2. Build from a list. Paste the values you want, one per line, and say whether a value should be an exact match or just contain, start or end with them. The builder escapes dots and other symbols, drops duplicates and groups shared parts.
3. Add values that must not match. For example, a comments page under the same path. Every value is tested, so you see the result before you save the filter.
4. Or test your own pattern. Switch to Test a pattern, paste the regex and some real values from your report. Each row shows GA4's result next to what a typical online tester says, and why they differ.
5. Copy the result. Paste it into GA4 using the steps shown under the pattern. If the checker found a fixable problem, such as an unescaped dot, it offers a corrected pattern.

What to do next in GA4

1. Report filter. Open the report, click + Add filter, select the dimension, set Match Type to matches regex (whole value) or matches partial regex (any part), paste the pattern and click Apply. Google's report filter page lists all match types.
2. Keep it under the limit. Report filter regex can be characters long. If your list is longer, group shared parts or split it across reports.
3. Audiences. In the audience builder, add a condition on the dimension, choose the regex option and paste the pattern. Each audience condition can hold characters.
4. Check the numbers. Compare the filtered total with an unfiltered report. If rows are missing, paste a few of the missing values into the test tab to see why.

Common GA4 regex mistakes

GA4 regex not working because of full match

The classic mistake: shoes finds nothing, because no page is called exactly “shoes”. Put .* before and after the part you want, or use the partial match type where GA4 offers one.

Does not match regex removes too much

With does not match partial regex, any value that contains the pattern anywhere is removed. A short pattern like test also removes “contest” and “latest”. Make the pattern specific, or use the full-match version with .* only where you need it.

GA4 regex lookahead not supported

Patterns copied from other tools often use (?!…) to exclude something. RE2 refuses lookaheads and lookbehinds. Use a second condition with does not match regex instead. JavaScript escapes such as é, \N{…} and \h, and repeat counts above 1,000, fail too; type the letter itself, since RE2 matches é as written.

Unescaped dots

example.com also matches “examplexcom”, because a dot means “any character”. Write example\.com. The same goes for IP addresses in internal traffic rules.

A pipe at the end

pricing|contact| has an empty last option. Google warns against ending a pattern with |: in a partial match the empty option matches every value.

GA4 regex examples