Let's look at some common categories of licenses you are likely to find on the web.

Creators of original work such as songs, books, or software often release their work under closed copyright protection. This means that, by default, they (or their publisher) have exclusive rights to use (for example, display or distribute) their work. If you want to use copyrighted images with an all rights reserved license, you need to do one of the following:

Authors are not required to include a copyright notice or license terms with their work. Copyright exists automatically in an original work of authorship once it is created in a tangible medium. So if you find an image online and there are no copyright notices or license terms, the safest course is to assume it is protected by copyright with all rights reserved.

If the image is released under a permissive license, such as MIT, BSD, or a suitable Creative Commons (CC) license, you do not need to pay a license fee or seek permission to use it. Still, there are various licensing conditions you will have to fulfill, which vary by license.

For example, you might have to:

You should consult the applicable license for the specific terms you will need to follow.

Note: You may come across the term "copyleft" in the context of permissive licenses. Copyleft licenses (such as the GNU General Public License (GPL) or "Share Alike" Creative Commons licenses) stipulate that derivative works need to be released under the same license as the original.

Copyleft licenses are prominent in the software world. The basic idea is that a new project built with the code of a copyleft-licensed project (this is known as a "fork" of the original software) will also need to be licensed under the same copyleft license. This ensures that the source code of the new project will also be made available for others to study and modify. Note that, in general, licenses that were drafted for software, such as the GPL, are not considered to be good licenses for non-software works as they were not drafted with non-software works in mind.

Explore the links provided earlier in this section to read about the different license types and the kinds of conditions they specify.

Work released into the public domain is sometimes referred to as "no rights reserved" — no copyright applies to it, and it can be used without permission and without having to fulfill any licensing conditions. Work can end up in the public domain by various means such as expiration of copyright, or specific waiving of rights.

One of the most effective ways to place work in the public domain is to license it under CC0, a specific creative commons license that provides a clear and unambiguous legal tool for this purpose.

When using public domain images, obtain proof that the image is in the public domain and keep the proof for your records. For example, take a screenshot of the original source with the licensing status clearly displayed, and consider adding a page to your website with a list of the images acquired along with their license requirements.