# Which Regular Expression engine and syntax is used by Mp3tag?

**URL:** https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713
**Category:** Support
**Created:** [January 30, 2020, 10:39am UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713 "2020-01-30T10:39:48Z")
**Posts on this page:** 1
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### Author: ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [January 30, 2020, 4:21pm UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713/8 "2020-01-30T16:21:02Z")

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Yes, as far as I know lookbehind must be fixed length. [Here](https://www.boost.org/doc/libs/1_70_0/libs/regex/doc/html/index.html) is the documentation for Boost.Regex included in Boost 1.70 which I'm _currently_ using.

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