Apple - How to Set a Short User Password in macOS Mojave and Later (10.14+)
You can also use the much more straightforward command:
pwpolicy -clearaccountpolicies
to remove the 4-character requirement for all users. The man
page gives other useful examples if you want to change the policy on a per-user basis.
Optionally, learn a bit of the regular expression language - regex (this may take a while) and you can use the one crafted below for a 4 character length password. Here’s how to retrieve the configuration, edit that file, and then load it into the system:
pwpolicy getaccountpolicies | awk 'NR>1' > ~/Desktop/file.plist
nano ~/Desktop/file.plist
Change the quoted part to your Regex.
policyAttributePassword matches '^$|.{4,}+'
pwpolicy setaccountpolicies ~/Desktop/file.plist
passwd
Presets:
^$|.{1,}+
: Any password. (Not the best Regex, but I didn't want to mess around with it too much.)
Confirmed this works with macOS Mojave (10.14).
Source: Modify pwpolicy in Sierra