Growth hacking is a marketing technique developed by technology startups which uses creativity, analytical thinking, and social metrics to sell products and gain exposure. It can be seen as part of the on line marketing eco-system, as in many cases Growth Hackers are simply good at using techniques such as search engine optimization, web site analytics, content marketing and A/B testing which are already mainstream. Growth hackers focus on low-cost and innovative alternatives to traditional marketing, i.e., utilizing social media and viral marketing instead of buying advertising through more traditional media such as radio, newspaper, and television. Growth hacking is particularly important for startups, as it allows for a "lean" launch that focuses on "growth first, budgets second." Facebook, Twitter, LinkedIn, AirBnB and Dropbox are all companies that use growth hacking techniques.