A couple of things to make German more consistent.

Most notably, the use of "ß" (the sharp s or sz [pronounced es-zed]) was adapted. Words with a short vocal cannot be followed by an "ß" now and have to be followed by an "ss".

Some words affected:

that: daß -> dass
castle: Schloß -> Schloss

This rule was in use in Austria-Hungary from 1879 -1901 by the way.

Another change was allowing the use of triple letters for combined words:

For example:

Ship journey = Schiff + Fahrt => Schifffahrt ≠ Schiffahrt (old)

There were a couple more changes with some exceptions for well-established words & some of the more controversial changes were retracted in 2006 but all in all it was a success.

The Wikipedia article does a better job at explaining some of the detail: https://en.m.wikipedia.org/wiki/German_orthography_reform_of_1996