One of the catchphrases on the internet is “Information wants to be free.” This creates the impression that anything you come across online is free for the using. Not quite.

The same laws that protect intellectual property elsewhere can get you in trouble for appropriating someone else’s words, images, music, video, and so on.

As with much else about the law, the devil is in the details. But you don’t need to hire a lawyer to stay safe. A basic understanding is often all you need. However, if you’re involved in a project that you’re uncertain about, by all means consult with an attorney specializing in intellectual property.

If you want to be as careful as possible, never put anyone else’s work on your website or blog without first asking permission. Never reuse anyone’s work either.

But this isn’t always possible, or necessary. The cornerstone of democracy is the free exchange of ideas, and our legal system promotes this in part through the fair use doctrine of the copyright law.

The key concept is “fair.” As a general rule, it’s more likely that you can fairly and legally reuse the work of others if your purpose is more for the common good than your own profit, if what you’re copying is factual rather than creative, if you copy a relatively small part of the work, or if your copying the work doesn’t diminish the originator’s ability to profit from it.

One fallacy is that unless the work is accompanied by a copyright symbol (a “c” within a circle), it doesn’t have copyright protection. This hasn’t been true in the U.S. since the country signed the international Berne Convention in 1989. The only necessity for copyright protection is that the work be created in a tangible form (rather than, for instance, existing in someone’s head).

Another copyright fallacy is that you must register a work with the U.S. Copyright Office for it to have copyright protection. Not so. Registering it, however, can make it possible to obtain greater monetary compensation and to be reimbursed attorney fees if infringement is proven.

Copyright and plagiarism are often confused because they are closely related. The former involves copying the form of the work of someone else, such as the words themselves. The latter involves claiming, explicitly or implicitly, someone else’s ideas as your own, even if you don’t copy the words or other forms used. Both can get you in trouble.

Typically, if you’re caught reusing someone else’s work online without permission and unfairly, you’ll receive a cease-and-desist letter or email. Once you take down the infringing material, that’s the end of it.

On the other hand, there’s a long history of copyright holders who were overzealous in protecting their work, trying to squash even the most harmless fair use. If you get an unjustified cease-and-desist communication, one option is to expose the party trying to squash your freedom of expression at the Chilling Effects Clearinghouse (www.chillingeffects.org).

To be fair, website owners often devote considerable time and resources to creating their content; you may be one such person or work for one such company. Commercial websites, for instance, leverage their online content to sell products or services or to enhance brand awareness.

You can learn of others lifting content from your site and using it at their sites through well-honed Google searches—just type in an unusual or unique string of text as your Google search term at your site.

Another tool is Copyscape (www.copyscape.com), a web service specifically designed to track web infringement. It’s available in free and pay versions.

With the free version, you go to the Copyscape site and type in the address of your webpage. Leveraging Google’s technology, it searches the web for pages with words copied from yours. One of its tricks is that even if another site moved sentences around or changed some keywords in a deliberate effort to be undetected, Copyscape can often still find it.

A beefed-up pay service of Copyscape called Copysentry, which starts at $4.95 per month, lets you set up automatic daily or weekly searches for copyright infringement. The results are emailed to you.