# What is the Unicode Default Case Conversion algorithm?

**URL:** <https://es.discourse.group/t/what-is-the-unicode-default-case-conversion-algorithm/613>\
**Category:** I have questions\
**Created:** [January 11, 2021, 4:29pm UTC](https://es.discourse.group/t/what-is-the-unicode-default-case-conversion-algorithm/613 "2021-01-11T16:29:11Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![conartist6](https://yyz2.discourse-cdn.com/free1/user_avatar/es.discourse.group/conartist6/32/515_2.png) [@conartist6](https://es.discourse.group/u/conartist6)\
**Post date:** [January 11, 2021, 4:29pm UTC](https://es.discourse.group/t/what-is-the-unicode-default-case-conversion-algorithm/613/1 "2021-01-11T16:29:12Z")

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I'm working on a streaming regex engine and I want to understand what the `i` flag does (when the `u` flag is not also present). I'm looking at [this section of the spec](https://tc39.es/ecma262/#sec-runtime-semantics-canonicalize-ch) which mentions the "Unicode Default Case Conversion algorithm" but does not define it.

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**Author:** ![conartist6](https://yyz2.discourse-cdn.com/free1/user_avatar/es.discourse.group/conartist6/32/515_2.png) [@conartist6](https://es.discourse.group/u/conartist6)\
**Post date:** [January 11, 2021, 4:37pm UTC](https://es.discourse.group/t/what-is-the-unicode-default-case-conversion-algorithm/613/2 "2021-01-11T16:37:21Z")

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Ah I think I found it in [the unicode spec](http://www.unicode.org/versions/Unicode6.2.0/ch03.pdf). Doesn't really help me, but I guess for my purposes what's under the hood is complex enough that I should stick with `String.fromCharCode(c).toUpperCase().charCodeAt(0)`.