World Wide Web (WWW) is expanding day-by-day in size with the increasing use of internet and increase in the amount of online text. In wide area networks, retrieving the relevant text is a challenging task for information retrieval. As most of the information requests are text based so the focus of paper is on the similarity measurement and performance evaluation of information retrieval techniques using the four similarity functions i.e. Jaccard, Cosine, Dice and Overlap. The performance evaluation of these similarity functions has been done for the similarity between the text entered by the user in the search engine and the documents retrieved for the entered text.