# Regular expression to convert case to Case, with exceptions
**URL:** https://community.mp3tag.de/t/regular-expression-to-convert-case-to-case-with-exceptions/6357
**Category:** Support
**Created:** [March 1, 2008, 4:30am UTC](https://community.mp3tag.de/t/regular-expression-to-convert-case-to-case-with-exceptions/6357 "2008-03-01T04:30:03Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@egd](https://community.mp3tag.de/u/egd)
#### Post date: [March 1, 2008, 4:30am UTC](https://community.mp3tag.de/t/regular-expression-to-convert-case-to-case-with-exceptions/6357/1 "2008-03-01T04:30:03Z")
Hi
Any idea how best to implement a regular expression or action to convert all words in all fields to "First Letter Caps" (other than the following [a, an, the, and, but, or, as, at, by, for, in, of, on, to], unless they are first word in the string)?
Thanks
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### Author:  [@egd](https://community.mp3tag.de/u/egd)
#### Post date: [March 1, 2008, 5:11am UTC](https://community.mp3tag.de/t/regular-expression-to-convert-case-to-case-with-exceptions/6357/2 "2008-03-01T05:11:57Z")
I think I've solved it, thx.
Field: \_ALL
RegEx: \s(a|an|and|as|at|by|but|for|in|of|on|or|out|the|to)(?=\s)
Replace matches with: $lower($0)
If you combine that with a Mixed Case Conversion action you pretty much end up with artist names, song titles and filenames formatted just how I like them 🙂
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### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [February 9, 2026, 12:20pm UTC](https://community.mp3tag.de/t/regular-expression-to-convert-case-to-case-with-exceptions/6357/3 "2026-02-09T12:20:48Z")