Online labor markets offer a cost-effective and efficient platform for conducting experiments, providing access to a large and diverse subject pool and enabling randomized controlled trials. This paper argues that online experiments can be as valid as traditional laboratory and field experiments, with significant cost and time savings. We replicate three classic experiments in an online labor market, confirming that subjects reverse decisions based on framing, exhibit pro-social preferences, and respond to priming. We also conduct a labor supply experiment, finding upward-sloping labor supply curves. Online experiments face unique validity threats, such as subject interaction and selection bias, but these can be mitigated through careful design. The external validity of online results can be as high as or even higher than traditional methods, depending on the research question. Online experiments offer a practical alternative to traditional methods, with the potential to significantly advance social sciences. We discuss the advantages of online labor markets, including their ability to provide diverse subjects and control for causal inference. We also address ethical challenges and the importance of transparency in experimental design. Overall, online experiments are a valuable tool for social science research, offering a cost-effective and efficient means of studying human behavior.Online labor markets offer a cost-effective and efficient platform for conducting experiments, providing access to a large and diverse subject pool and enabling randomized controlled trials. This paper argues that online experiments can be as valid as traditional laboratory and field experiments, with significant cost and time savings. We replicate three classic experiments in an online labor market, confirming that subjects reverse decisions based on framing, exhibit pro-social preferences, and respond to priming. We also conduct a labor supply experiment, finding upward-sloping labor supply curves. Online experiments face unique validity threats, such as subject interaction and selection bias, but these can be mitigated through careful design. The external validity of online results can be as high as or even higher than traditional methods, depending on the research question. Online experiments offer a practical alternative to traditional methods, with the potential to significantly advance social sciences. We discuss the advantages of online labor markets, including their ability to provide diverse subjects and control for causal inference. We also address ethical challenges and the importance of transparency in experimental design. Overall, online experiments are a valuable tool for social science research, offering a cost-effective and efficient means of studying human behavior.