The invention relates to a device and a method for analyzing performances of a web application capable of performing a process of on-the-fly anonymization (400) of production data, said production data being generated following a benchmark request message (MR1, MR2′) transmitted to said web application, said anonymization process (400) being carried out by a first electronic communication device (10) capable of Identifying, from a sensitive data identification repository (14), data to be anonymized in the response message (MRR1, MRR2); Generating, from an anonymization repository (15), anonymized data from previously identified data to be anonymized; and Generating, from the anonymized data and from the response message (MRR2), an anonymized response message (MRR2′).