In practice
The test is intent and equivalence: adapting layout by device is normal, swapping the text a bot sees is not.
Dynamic rendering sits close to the line and stays acceptable only while both versions carry the same content.
Why it matters
It is a direct violation of search engine guidelines and carries manual penalties up to full removal.
It is also frequently accidental — a personalisation layer or a geo-redirect that treats bots as a separate audience.
Related terms