How does copyright work? What it covers and how long it lasts

Copyright is a legal right that gives the creator of an original work, such as a book, song, photo, film or piece of software, the exclusive power to copy it, share it and adapt it for a limited time. In most countries copyright does its work without any paperwork: it arises automatically when the work is created (in the US, once it is fixed), it protects the expression and not the idea behind it, and it ends after a set term, when the work becomes free to use.

In short

• No registration or © symbol is needed: a sketch, an email or a voice memo is protected as soon as it exists in fixed form.
• Copyright guards the particular words, notes or images, not the facts, ideas or methods they express.
• Fair use, in the United States, and fair dealing, in the UK and elsewhere, let people use protected work without permission for purposes such as criticism, news and teaching.

Rules differ by country. This note explains the general system, with United States and European examples, and isn't legal advice.

What does copyright protect, and what doesn't it?

Copyright protects "original works of authorship fixed in any tangible medium of expression", in the words of the US Copyright Act (17 U.S.C. § 102). Each part of that phrase does work. Original means the author made it, with at least a small spark of creativity; it need not be good or new to the world. Fixed means recorded in a form that lasts, on paper, a hard drive or a recording. Under US law, a song you improvise and forget is not protected; the same song on your phone's voice memo is. Some countries, such as France, don't require fixation at all.

The same section draws the most important line in the subject: copyright never covers "any idea, procedure, process, system, method of operation, concept, principle, or discovery". A recipe's list of ingredients, the plot idea of a boy wizard at boarding school, the rules of a card game and the facts in a news story are free to all. What is protected is how someone expressed them: the recipe writer's sentences, the actual novel, the rulebook's wording, the reporter's article. Names, short phrases and titles are generally not protected by copyright at all, though they may be protected as trademarks.

The owner gets a bundle of exclusive rights: to make copies, to make derivative works such as translations, sequels or film adaptations, to distribute copies, and to perform or display the work in public. Anyone else doing those things without permission, and without an exception that applies, infringes.

Do you have to register a copyright?

No. Since the Berne Convention of 1886, now joined by most of the world's countries, protection may not depend on any formality, the World Intellectual Property Organization explains. The © notice is optional.

The United States adds one practical twist. Registration with the Copyright Office is voluntary, but the owner of a US work must register before suing for infringement, and statutory damages, which a court can award without proof of lost money, are generally only available if the work was registered before the infringement began or soon after publication. So creators who expect to enforce their rights often register early.

How long does copyright last?

For most works by a known person, copyright lasts for the author's life plus a fixed number of years. The Berne Convention sets a minimum of life plus 50 years. The United States and the European Union both use life plus 70, the US since the Copyright Term Extension Act of 1998. In the US, works made for hire by a company, and anonymous works, last 95 years from publication or 120 from creation, whichever ends first, according to the Copyright Office.

A worked example under life plus 70: a novelist who wrote a book in 1990 and died in 2010 holds the copyright for life, and her heirs hold it for 70 years more: 2010 + 70 = 2080. Terms run to the end of the calendar year, so the book is protected through 31 December 2080 and enters the public domain on 1 January 2081, in the United States and the European Union alike. Older US works follow different rules based on their publication date, which that note works through.

How is copyright different from patents and trademarks?

People often lump the three together as intellectual property. They protect different things, for different terms, in different ways.

	Copyright	Patent	Trademark
Protects	Creative expression: text, music, art, film, code	Inventions: new, useful, non-obvious machines, processes, compounds	Signs that identify a seller: names, logos, slogans
How you get it	Automatically, on fixation	Granted after examination by a patent office	By using it in trade; registration strengthens it
How long	Life plus 50 to 70 years in most countries	Usually 20 years from filing	As long as it is used and renewed
Stops others from	Copying and adapting the work	Making, using or selling the invention at all	Using a confusingly similar sign on similar goods

The patent column holds the sharpest contrast. Copyright stops copying, so someone who writes a near-identical poem independently does not infringe. A patent stops everyone, even an inventor who never saw the original.

What is fair use?

Fair use is the US exception that lets people use protected work without permission when the purpose and the amount make it fair. Courts weigh four factors set out in 17 U.S.C. § 107: the purpose and character of the use, including whether it is commercial or transforms the work into something new; the nature of the work, factual or creative; how much is used; and the effect on the market for the original. No single factor decides, and there is no safe word count.

Run two uses through the factors:

1. A book reviewer quotes three sentences from a new novel to show its style. The purpose is criticism and transforms the quote into commentary; the amount is tiny; and a review does not replace buying the book. This is a classic fair use.
2. A company plays a whole popular song under its television advertisement. The use is commercial and adds nothing new to the song; it takes all of it; and it replaces exactly the license the songwriter sells to advertisers. This fails.

Most real cases fall between those two, which is why fair use is decided case by case. The UK, Canada, Australia and India use a narrower idea called fair dealing: a closed list of purposes, such as research, private study, criticism, review, quotation, news reporting and, in the UK since 2014, parody and pastiche, each of which must also be fair in amount, as the UK government's guidance sets out. Trying to suppress a fair use can backfire, as the Streisand effect describes.

Does copyright cover AI, and can AI be trained on copyrighted work?

Two separate questions arise with generative AI. The first, who owns what a model makes, has a clearer answer in the US: copyright requires a human author. In March 2025 a federal appeals court in Washington, D.C., upheld the Copyright Office's refusal to register an image credited to an AI system alone, in Thaler v. Perlmutter. The Office's January 2025 report on copyrightability said prompts alone generally don't give a person enough control to be an author, though human selection, arrangement and editing of AI material can be protected.

The second question, whether copying works to train a model is lawful, is open.

Still argued

AI developers argue that training is a transformative use: the model learns statistical patterns and doesn't store or republish the works. Authors, artists and publishers argue that it copies their work at industrial scale to build products that compete with them. US trial courts have split by facts. In February 2025, in Thomson Reuters v. Ross Intelligence, a federal judge ruled that copying legal summaries to build a competing, non-generative research tool was not fair use. In June 2025, two judges in San Francisco ruled in Bartz v. Anthropic and Kadrey v. Meta that training on books was fair use on the records before them, with limits; Anthropic then agreed to pay $1.5 billion to settle the claims over pirated copies, and the court gave the settlement final approval in July 2026, as Mealey's reported. The New York Times's suit against OpenAI and Microsoft, filed in December 2023, is one of dozens of similar suits in US courts. In May 2025 the Copyright Office said some training will be fair use and some will not, depending on the use and its effect on markets. The European Union's 2019 copyright directive allows commercial text and data mining of lawfully accessed works unless the rights holder has reserved its rights, for online content in a machine-readable way. Trial-court rulings bind no other court, so each new case argues the question afresh.

A related puzzle, what buying a token tied to an image gives you, is taken apart in what an NFT is: usually not the copyright. Copyright is one of the rules the law uses to balance two goods, rewarding creators and leaving culture free to build on itself.

Check yourself

• Without looking back: why, under US law, does a song you hum in the shower have no copyright, while the same tune on a voice memo does?
• Using the four factors, explain why a review that quotes a novel is fair use and an advert that plays a whole song is not.
• What can a patent stop that a copyright cannot?

Sources

• What is copyright? — U.S. Copyright Office
• Subject matter and scope of copyright, 17 U.S.C. chapter 1 — U.S. Copyright Office
• 17 U.S.C. § 107, limitations on exclusive rights: fair use — Legal Information Institute, Cornell Law School
• Summary of the Berne Convention for the Protection of Literary and Artistic Works — World Intellectual Property Organization
• Exceptions to copyright — UK Intellectual Property Office
• Copyright and Artificial Intelligence — U.S. Copyright Office, 2024–2025