The text of 17 U.S.C. § 107, the fair use provision of the Copyright Act of 1976, reads:

Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phono records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include—

(1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;

(2) the nature of the copyrighted work;

(3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and

(4) the effect of the use upon the potential market for or value of the copyrighted work.

The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.

What on earth does all that mean? Well, on the face of it, none of it is terribly helpful in making particular fair use determinations, and it certainly doesn’t tell you exactly which uses will be fair and which won’t. As Judge Pierre N. Leval wrote in the Authors Guild v. Google decision:

The statute’s wording…does not furnish standards for recognition of fair use. Its instruction to consider the “purpose and character” of the secondary use and the “nature” of the copyrighted work does not explain what types of “purpose and character” or “nature” favor a finding of fair use and which do not.

Nor does the statute tell you exactly how to tell how much is too much to use under factor three, or how to determine the effect of the use on the market under factor four. And, these four factors are not exclusive—courts shall consider them, but they may consider others. The Supreme Court has said that the factors must be weighed together in light of the purposes of copyright. Courts have said repeatedly that the factors can’t be simply tallied together in a ledger. While some copyright “guidance” simply advises that you walk through the four statutory factors to decide whether your use is fair, the factors on their own simply are not very useful.

And what about the part that precedes the four factors, the so-called “preamble” that lists “purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research” as potential fair uses? While the list of favored purposes can be helpful, and encouraging, it is not a free pass. A use for teaching or research will still have to be considered on its own facts, weighing the factors together. So, neither the list of exemplary fair use purposes nor the four factors provides definitive guidance to a would-be fair user.

That’s not an accident—when Congress adopted this language in 1976, it meant to describe generally a broad area of discretion for courts, not to tie their hands. The real key to understanding how fair use works is knowing what courts have done with these factors. The remaining portions of this box describe some of the lessons scholars have drawn from examining fair use cases.

The history of fair use cases of all kinds shows that judges return again and again to two key analytical questions:

• Did the use “transform” the material taken from the copyrighted work by using it for a broadly beneficial purpose different from that of the original, or did it just repeat the work for the same intent and value as the original?
• Was the material taken appropriate in kind and amount, considering the nature of the copyrighted work and of the use?

These two questions breathe life into the “four factors.” The first addresses the first two factors by telling you what purposes are favored and how to evaluate the nature of the work used, and the second tells you how to tell how much is too much under the third factor. Both key questions touch on the so-called “fourth factor,” whether the use will cause excessive economic harm to the copyright owner.

If the answers to these two questions are “yes,” a court is likely to find a use fair—even if the work is used in its entirety. Because that is true, the risk of a challenge to such a use is dramatically reduced.

Fair use ensures that copyright owners do not have a monopoly over transformative uses of their works. The converse is also true. When a use merely supplants a copyright owner’s core market rather than having a transformative purpose, it is unlikely to be fair. Thus, for example, a library clearly cannot acquire current books for its collection simply by photocopying or scanning published editions.

In the recent Google Books decision, Judge Leval suggested that even uses for transformative purposes may be unfair if they provide the public with access to enough of the underlying work to serve as a substitute on the market for that work.

In cases decided since the early 1990s, the courts have made it clear that in order for a use to be considered “transformative,” it need not be one that modifies or literally revises copyrighted material. In fact, uses that repurpose or decontextualize copyrighted content in order to present it to a new audience for a new purpose can qualify as well. The courts also have taught that the more coherent an account the user can give of how and why the material was borrowed, the more likely the use is to be considered transformative.

Examples may be the best way to get a sense of what sorts of uses are transformative. Here are some of the uses courts have found transformative:

• In the landmark case Campbell v. Acuff-Rose, the Supreme Court found that using enough of a work to “conjure up” its essence as part of a parody was transformative. In this case, it was 2 Live Crew using the core musical elements of Roy Orbison’s “Oh Pretty Woman.” In another parody case, Brownmark v. Comedy Partners, the 7th Circuit Court of Appeals found it was transformative for the show South Park to use elements of the defendant’s song and music video to make fun of it.

• In Sundeman v. Seajays the 11th Circuit court of appeals held that a scholar’s critical essay and lecture, which incorporated excerpts from an unpublished manuscript called Blood of My Blood, was transformative:

  A reading of Blythe’s paper clearly indicates that she attempted to shed light on Rawlings’ development as a young author, review the quality of Blood of My Blood, and comment on the relationship between Rawlings and her mother. The “further purpose” and “different character” of Blythe’s work make it transformative, rather than an attempt to merely supersede Blood of My Blood.

• In Authors Guild v. HathiTrust, the Second Circuit Court of Appeals found that it was fair use for the HathiTrust, a non-profit formed by a group of research libraries, to copy millions of books onto redundant servers in order to preserve the books, provide a search and text mining tool for researchers, and provide accessible copies of books to print-disabled patrons.
• In Cariou v. Prince, the Second Circuit Court of Appeals found that it was transformative for the artist Richard Prince to copy from photographer Patrick Cariou’s black and white photos depicting Rastafarians in Jamaica to create his own mixed-media collages. The court emphasized the dramatically different aesthetic styles of Prince and Cariou (Prince’s extremely large, loud, irreverent and chaotic paintings vs. Cariou’s serene and respectful photos presented in a modest book), as well as the different markets to which their art was addressed (Prince’s works are collected by famous celebrities who pay millions for canvases, while Cariou’s books are sold in small stores for a modest price).

Fair use guidance is often given in terms of how much one can safely copy from a given kind of work without permission–how many words, pages, minutes, or chapters, or what percentage of the whole can be taken without permission. Unfortunately, the law doesn’t really work that way, and there is no magic number or set of numbers that will guarantee your use is fair. This is because courts always consider both quantity and quality of the portion used, and they judge whether the amount is appropriate by looking at the context of the use.

That doesn’t mean you can’t tell how much is too much, though; it just means the answer depends on your context. But if you’re willing to think a little bit about your planned use, it is not difficult to know how much fair use will allow you to use for your purpose. Courts looking at amount generally consider two things:

• What is the appropriate amount for your new purpose?
• Have you provided the public with enough of the work to serve as a market substitute for the original work?

Let’s take them in turn.

Appropriate to purpose

For the last 20 years or so, courts have been focusing more and more on the question of the user’s legitimate purpose. This is the first part of the fair use analysis, and once the courts decide your purpose is legitimate, that decision deeply colors the rest of the analysis. In particular, following the Supreme Court’s landmark fair use decision in the Campbell v. Acuff-Rose case, once courts find that a use is transformative, they consider amount primarily in terms of whether the amount used is appropriate to the transformative purpose. This determination is therefore context-sensitive, and the user is the best person to decide what amount is the right amount for their new use.

For example, a parody song like the 2 Live Crew take on Roy Orbison’s “Oh Pretty Woman” might appropriately use a substantial amount of the original song so that listeners will clearly understand the target of the parody. Or an illustrated history of the Grateful Dead might appropriately reproduce complete images of concert posters (but at a reduced size and resolution) in order to give the reader a sense of the band’s history. A search engine may need to copy entire works into its database to help researchers find relevant websites, but a “snippet” or a “thumbnail” would be the appropriate amount to actually reveal to the public for that purpose. Similarly, a “lexicon” for Harry Potter aficionados may quote relevant passages from J.K. Rowling’s stories to give a sense of the subjects it catalogs (monsters, spells, key characters and locations, etc.), but the court found that the author of the Harry Potter Lexicon went too far in taking lengthy narrative passages more appropriate to a short story collection than a reference book. The key in each case is to ask how your legitimate activity is different from simple copying, and to ensure you use an amount appropriate to your new purpose.

Importantly, the standard here is “appropriateness,” not “necessity.” Some guides to fair use mistakenly advise that only the barest minimum amount necessary to achieve a novel purpose will be protected under fair use, but that is not the law. Courts, including the Supreme Court, have said time and again that a fair user should have latitude to determine the appropriate amount for her use, and need not confine herself to a bare minimum.

Avoid market substitution

Another factor, which is similar but distinct from the question of appropriate length for purpose, is whether your use provides the public with enough of the original work to serve as a market substitute for it. Generally speaking, when your use is for a novel purpose like criticism or commentary, there is very little chance that someone would use your work as a substitute for the work you quote. While it is common to use book reviews as a way to know whether to buy a book, no one reads book reviews instead of reading the book. The question of appropriateness to purpose intertwines with market substitution, here, because a use that provides a market substitution is highly unlikely to be appropriate to a genuinely new purpose of the kind fair use protects.

However, in some cases, legitimate new uses do involve copying a larger amount of the work, even the entire work, and it may be important to ensure in those cases that you prevent broad public access to copies that might compete unfairly with the original work. For example, some technological uses like text mining or the creation of a search engine involve wholesale copying of entire works, but that copying is done “behind the curtain,” so to speak—only a computer actually “reads” the works in their entirety. Or, in the case of images, it is often appropriate to reproduce entire images in connection with legitimate uses like search or criticism, but the size or resolution of the images can be reduced to avoid substitution for access to the images for ordinary consumption.

Perhaps the best sources of guidance about what constitutes fair use are the various best practices guides developed by practice communities, starting with documentary filmmakers in 2004. These statements combine core insights from courts—like the importance of a legitimate new purpose, and avoiding market substitution—with insights from practitioners about how to tailor legitimate fair uses that recur in their community. These guides replace the one-size-fits-all approach of numerical guidelines with a reasoned and nuanced approach tailored to context.

The Center for Media and Social Impact at American University has played a major role in developing many of these statements, and collects all of them on its website.

Every three years the Librarian of Congress (advised by the Copyright Office) issues a set of exceptions to the 1201 rules to allow for lawful uses that might otherwise be discouraged by the law. Educators have participated in this process, which began in 2000, for many years, and have successfully obtained exceptions that have grown incrementally over time to encompass more uses, more types of media, and more users.

The latest set of rules, released in 2015, allow faculty and (in some cases) students to copy short portions of protected works for use in criticism or commentary where close analysis of the clip is necessary, for the following formats: DVD, streaming video delivery, and (in some cases) Blu-ray. While the prior rules had allowed use of DVD and streaming for these purposes, access to Blu-ray is new this cycle.

The new rules allow educational uses of these formats in several different contexts, with some differences in the rules depending on where the use is taking place. The categories of educational use are:

• Colleges and universities, for faculty and students
• Massive Open Online Courses, for faculty only, and must comply with certain provisions of the TEACH Act
• K–12 education, for teachers (excluding Blu-ray) and students (only using “screen capture” software, not direct copying, aka “ripping”)
• Courses taught in libraries, museums, and other nonprofit entities with educational missions, for teachers only, and only using “screen capture” software, not direct copying.

As you can see, the provisions are complex, and the process of obtaining them was very complex. Different rules will apply to the same course depending on where it is taught (AP US History in high school versus US History 101 in college versus Intro to US History taught at an extension program in a public library). Different media, different software tools, and different participants are covered depending on context. That said, the rules are much broader and more flexible than they have been in the past, and they cover many, many lawful uses in higher education.