# Am I right in thinking Lucene regex doesn't support lookahead?
**URL:** https://discuss.elastic.co/t/am-i-right-in-thinking-lucene-regex-doesnt-support-lookahead/346882
**Category:** Kibana
**Created:** [November 10, 2023, 4:02pm UTC](https://discuss.elastic.co/t/am-i-right-in-thinking-lucene-regex-doesnt-support-lookahead/346882 "2023-11-10T16:02:41Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@dmgeurts](https://discuss.elastic.co/u/dmgeurts)
#### Post date: [November 10, 2023, 4:02pm UTC](https://discuss.elastic.co/t/am-i-right-in-thinking-lucene-regex-doesnt-support-lookahead/346882/1 "2023-11-10T16:02:41Z")
Creating a new visualisation I just came across a curious case of regex filtering.
The following Regex Lucene filter is what I had to use to show only values containing both upper and lower caps:
**Works**
`dns.question.name:/.*[A-Z].*/ and NOT (dns.question.name:/.*[A-Z].*/ and NOT dns.question.name:/.*[a-z].*/)`
It looks pretty convoluted, but it must be done this way to not match entries in all lower- or all uppercase. The following would be simpler from a regex point of view but doesn't work. Presumably due to the lookahead?
**Doesn't work**
`dns.question.name:/(?=.*[a-z])(?=.*[A-Z]).*/`
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [December 8, 2023, 4:02pm UTC](https://discuss.elastic.co/t/am-i-right-in-thinking-lucene-regex-doesnt-support-lookahead/346882/2 "2023-12-08T16:02:57Z")
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