Does copyright apply to Stack Exchange answers and comments?
<p>So I asked a question on <a href="https://worldbuilding.stackexchange.com/">Worldbuilding Stack Exchange</a>, and I got an answer that I really enjoyed. I loved the way the person described it. So I thought, is it okay to copy this and use it in other things?</p>
<p>Short question: are Stack Exchange questions public domain?</p>

<p>Stack Exchange questions are not public domain, they are protected by copyright. Authors have granted a <a href="https://stackoverflow.com/legal/terms-of-service/public#licensing">license</a> under Subscriber Content, specifically content</p>
<blockquote>
<p>is perpetually and irrevocably licensed to Stack Overflow on a
worldwide, royalty-free, non-exclusive basis pursuant to Creative
Commons licensing terms (CC BY-SA 4.0)</p>
</blockquote>
<p>As long as you comply with the terms of the CC BY-SA 4.0 license, you may copy user content.</p>

<p>It is protected by copyright, like almost everything with a lapse of originality created nowadays.</p>
<p>You can use it under the terms of the license <a href="https://creativecommons.org/licenses/by-sa/4.0/" rel="nofollow noreferrer">Creative Commons Attribution ShareAlike 4.0</a>, as noted by user6726.</p>
<p>Plus, you could also ask for an additional permission from the author. Some might require some monetary compensation in exchange of giving you an additional license. Others would be fine with just being credited by name, dropping the requisites of linking to the license and their original work. Others won't care at all. I think most people on world building SE would be delighted just of getting a copy of an actual book where their idea was used and they appear credited for it.</p>
<p>While not strictly required by the license, I also recommend you to explicitly thank for their answers and tell how you ended up using it, even if you can only that you indeed had the book on print a long time later (StackExchange will notify of new comments on your answers). It's very nice when people receive such kind of feedback.</p>
<p>(Obviously, in addition of having upvoted the answer when you found it)</p>

<p>Yes, Stack Exchange answers, questions, and comments are all copyrighted by their authors (and thus not in the public domain), and licensed to anyone (including both you and Stack Exchange) under the <a href="https://creativecommons.org/licenses/by-sa/4.0/" rel="nofollow noreferrer">CC BY-SA 4.0 license</a>.</p>
<p>That means that you must do two things when using material from Stack Exchange sites:</p>
<ol>
<li><p><strong>Provide attribution</strong>: You must credit the original author, provide a link to the content, indicate that it's under the CC BY-SA license, and indicate if changes were made.  Stack Exchange provides <a href="https://stackoverflow.blog/2009/06/25/attribution-required/">this guidance</a>:</p>
<blockquote>
<ol>
<li>Visually indicate that the content is from Stack Overflow or the Stack Exchange network in some way. It doesn’t have to be obnoxious; a discreet text blurb is fine.</li>
<li>Hyperlink directly to the original question on the source site (e.g., <a href="http://stackoverflow.com/questions/12345">http://stackoverflow.com/questions/12345</a>)</li>
<li>Show the author names for every question and answer</li>
<li>Hyperlink each author name directly back to their user profile page on the source site (e.g., <a href="http://stackoverflow.com/users/12345/username">http://stackoverflow.com/users/12345/username</a>)</li>
</ol>
</blockquote>
</li>
<li><p><strong>Share your derivative work under the same license</strong>: If you remix, transform, or build upon the material, you must license your creation under the same license.</p>
</li>
</ol>

copyright public-domain