Methods for automatically generating a wrapper for extracting web data and corresponding computer systems are disclosed. In one arrangement, a first wrapper is used to generate a second wrapper. The first wrapper extracts target data from one or more target web pages hosted by one or more target web servers. The second wrapper is capable of extracting the same target data from the same one or more target web pages without using a web browser engine to perform a) sending requests to the one or more target web servers, and/or b) processing replies from the one or more target web servers. The generation of the second wrapper comprises analysing one or both of the following: (i) code defining the first wrapper, (ii) interactions between the first wrapper and the one or more target web servers that occur during execution of the first wrapper.