In the United States, fair use is determined by a judge, who analyzes a specific case based on a set of principles. Different countries have different rules about when it’s okay to use material without the copyright owner’s permission. For example, in the United States, works of commentary, criticism, research, teaching, or news reporting might be considered fair use. Some other countries have a similar idea called fair dealing that may work differently.

1. The purpose and character, of the use, including whether such use is of commercial nature or is for nonprofit educational purposes

Courts typically focus on whether the use is “transformative.” That is, whether it adds new expression or meaning to the original, or whether it merely copies from the original. Commercial uses are less likely to be considered fair, though it’s possible to monetize a video and still have one's usage be a fair use.

2. The nature of the copyright work

Using material from primarily factual works is more likely to be fair than using purely fictional works.

3. The amount and substantiality of the portion used in relation to the copyrighted work as a whole

Borrowing small bits of material from an original work is more likely to be considered fair use than borrowing large portions. However, even a small taking may weigh against fair use in some situations if it constitutes the “heart” of the work.

4. The effect of the use upon the potential market for, or value of, the copyrighted work

Uses that harm the copyright owner’s ability to profit from his or her original work are less likely to be fair uses. Courts have sometimes made an exception under this factor in cases involving parodies.

Your usage is not automatically fair use when you use copyrighted material you don’t own, even if you give credit to the copyright owner, post a disclaimer such as "no infringement intended," or add some original content to someone else's content. In particular, uses that do not comment on or criticize the content used (and that instead serve as a substitute for the original work) are unlikely to be considered fair uses.

Transformativeness is usually a key in the fair use analysis. Giving credit to the owner of a copyrighted work won’t by itself turn a non-transformative copy of their material into fair use. Phrases such as “all rights go to the author” and “I do not own” do not automatically mean you are making fair use of that material - nor do they mean you have the copyright owner’s permission.

There are no magic words that will guarantee you are protected by fair use when you use copyrighted material you don’t own. Including the phrase “no infringement intended” won't automatically protect you from a claim of copyright infringement.

Courts will look carefully at the purpose of your use in evaluating whether it is fair. Declaring your upload to be “for entertainment purposes only,” for example, is unlikely to tip the scales in the fair use balancing test. Similarly, “non-profit” uses are favored in the fair use analysis, but it’s not an automatic defense by itself.

Even if you’ve added a little something of your own to someone else’s content, your use might still not be considered a fair one - particularly if your creation fails to add new expression, meaning, or message to the original. As with all the other cases discussed here, courts will consider all four factors of the fair use test, including the quantity of the original used.