Depending on your point of view, releasing a person's identifying information on the internet might be one of the few ways to hold someone accountable for hateful actions or an avenue to unleashing hate upon an undeserving someone else. Trying to out white supremacists who participated in political violence? You might support it. But what about a person misidentified during those efforts? Or what about the other side using the same tactics to target opponents with harassment?
Either way, doxing has remained, thus far, a largely legal activity. But that doesn't mean doxing can't stem from or lead to a crime.
The source of the information can determine doxing's legality. Most often, posted identifying information was obtained, if not easily or cheaply, from publicly available resources. For instance, simply posting a person's photo from a public demonstration and asking for help identifying the person would not generally be illegal. If you hacked that person's email account to post their messages or Social Security number, that would be.
If a person didn't break the law to obtain the identifying information involved, publishing the information likely wouldn't break the law either.
Obviously, the intent in any doxing is for the target to experience some repercussions, from public shame or ostracization to being fired from a job. However, if doxing is done with the intent to threaten or harass someone, or leads to threats or harassment, those actions can be illegal. "You can post it as long as there is nothing nefarious about it," LAPD cyber crimes detective Andrew Kleinick told Daily Beast. "They are public figures and that kind of thing happens. It's not right, [but] I know of no crime."
Kleinick was talking about the online posting of celebrities' personal information a few years back, but hits on an important point. The target of the doxing could matter, as well. While not a criminal law, most states allow invasion of privacy lawsuits for the public disclosure of private facts. A defense to such a lawsuit can be that there is a legitimate public interest in the information, a bar that is much higher for private individuals than for public figures.
Before you dox, or if you've been charged with a doxing-related crime, contact a local criminal law attorney.