The new Machinery Regulation (EU) 2023/1230, like the previous Machinery Directive, is a document intended for machinery manufacturers. However, operators must also be familiar with it. For example, the topic of “substantial modification” is now regulated consistently across Europe, but the content differs slightly from the German BMAS interpretation paper. In case of a substantial modification, an operator becomes a manufacturer and must comply with the requirements of the Machinery Regulation. This presentation addresses the question of when a substantial modification occurs, what consequences this has for operators, where the pitfalls lie, and which topics are still open. To round things off, the relation to the Industrial Safety Regulation (Betriebssicherheitsverordnung) will be briefly discussed.