How do you update "yarn" to the latest version, 1.13.0?

The question shows that yarn has been upgraded with npm install yarn -g to 1.13.0 but the yarn command is still showing an older version

D:\test>yarn -v
1.12.3

The most likely problem is because the executed yarn version is as expected, C:\Users\myuser\AppData\Roaming\npm\yarn. Check which version of yarn you are invoking with

D:\test>where yarn

Upgrading Yarn

@Whatatimetobealive's answer is the best option to upgrade yarn. If for some reason you cannot use choco, brew, npm or your package manager to install yarn, you can try using yarn itself.

$ yarn global add yarn

Unfortunately we cannot use yarn to update itself until the yarn self-update command is fixed.

There is a known bug on npm update yarn -g here is the related GitHub issue so you should use this instead:

npm install -g yarn

Alternatively, you can install brew first than update trough brew like this:

brew upgrade yarn

If you're using Windows you can find a brew alternative, such as choco, and update with like this:

choco upgrade yarn