Internet is the biggest information source on the planet. It is difficult to edit the huge amount of data on the web manually. So the concept of web data extraction system was introduced. Web data extraction has a wide range of applications, but web data extraction is a major problem that has been studied by means of different scientific tools. This survey provides an overview of the web data extraction techniques, mainly focuses on automatic web data extraction techniques and also compares them based on the methods used for web data extraction.