Dynamic Serving
Returning different HTML and CSS from the same URL depending on the visitor's device, detected from the user agent string.
Analogy Mental model
One entrance, one doorman. Adults are shown to a table with the main menu, children are given a high chair and a colouring sheet. The address never changes.
In practice What you actually do
Older large-scale commerce platforms still work this way. If you inherit one, confirm the response includes the appropriate vary header so caches store the two versions separately and the correct crawler receives the correct one.
Where people get burned Pitfalls
The classic failure is a team adding content, internal links, and markup to the desktop template while forgetting the mobile one. Under mobile-first indexing, only the mobile version counts, so the desktop work is invisible.
This entry was written in English from the Chinese original, not machine-translated. Read the Chinese version →