Now that online communication has become a routine part of everyday life, it is important for teens to understand how constitutional principles apply in the digital age. According to the courts, the First Amendment right to free speech applies online. However, this guarantee is subject to the same limits as in person and in print: citizens can't defame, libel, or slander others. But due to the anonymity, speed, and enormous reach of the Internet, it is unfortunately easier than ever to destroy a person's reputation by posting false information online. The author explains what kinds of speech constitute defamation, including libel and slander, and how to handle the issue when it arises in teen life. Related issues, including cyberbullying and hate speech, are also addressed.