Dynamic pages are written, in whole or in part, as they are needed. They are more difficult to design, but they are useful when you need to present different information at different times.

Dynamic pages can be combined with online databases. This is especially useful when the data change frequently, as in catalogs and price lists. This avoids many problems that arise when the data are scattered through the website. It also permits catalog entries to be added and deleted by updating the database - the program then constructs the correct number of web pages.

Another common use of dynamic pages is to process user inputs from forms. The program can test for missing or erroneous entries, and it can return different pages depending on the visitor’s request.