This bachelor thesis looks at developers knowledge about web security both regarding their own view on their knowledge and their actual knowledge about vulnerabilities and how you mitigate against them. Web developers knowledge regarding web security are becoming more and more important as more applications and services moves to the web and more and more items become connected to the internet. We are doing this by conducting a survey among developers that are currently studying in the field or are working in the field to get a grip on how the knowledge is regarding the most common security concepts. What we saw was that the result varies between the different concepts and many lack much of the knowledge in web security that is getting increasingly more important to have.