What does copyleft mean?
Copyleft is a licensing approach that allows a work to be used, copied, modified, and distributed while requiring derivative or redistributed versions to preserve the same or equivalent freedoms. It is especially influential in software, where public licenses have made it possible for users to inspect, repair, improve, and share programs. The central mechanism is reciprocity: rather than withdrawing permissions for reuse, a copyleft license uses conditions to ensure that later versions retain comparable rights. Copyleft is often associated with free software, but the idea can apply to documents, artwork, educational materials, and other works. It is also commonly used politically or metaphorically to describe the principle of sharing resources so that others can build upon them. Although it relies on copyright law to enforce its conditions, copyleft is not simply the opposite of ownership; it is a way of using legal permissions to protect continuing access and modification.
A licensing principle, license, or arrangement that permits broad use and modification of a work while requiring derivative or redistributed versions to remain under the same or equivalent terms.
"The project adopted a copyleft to prevent commercial companies from taking the software without sharing their modifications."
The word may refer collectively to the licensing principle or to a particular license embodying it.
Of, relating to, or licensed under a system that preserves broad rights to use, modify, and redistribute a work on reciprocal terms.
"The organization published its research data as copyleft material."
The attributive form is especially common before words such as license, software, and culture.
To license a work or make it available under copyleft terms.
"The developers decided to copyleft the code after the project moved to an open development model."
This verbal use is less common than the attributive adjective and the noun.
Use the plural for distinct copyleft licenses or licensing arrangements; the general copyleft principle is normally uncountable.
"The organization maintains two copylefts for its software projects."
Coined in 1989, copyleft flipped the idea of copyright: keep the rights, and make sure everyone who builds on the work inherits those rights too.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does copyleft come from?
Copyleft is an English compound formed from copy and left, with left used in deliberate contrast to copyright. Richard Stallman coined the term in 1989 while developing a practical licensing system for freely shareable software. Its construction reverses the usual direction of copyright by retaining legal restrictions but making them protect the right to share and modify the work.
Related word forms
How copyleft is actually used
Copyleft is most common in software, publishing, education, and discussions of intellectual property. In political or cultural contexts it can be used more broadly as a metaphor for reciprocal sharing, though such uses may be rhetorical rather than references to a specific legal license.
Easily confused with copyleft
Copyright reserves or grants specified rights in a work, whereas copyleft uses licensing to preserve broad rights to use and modify the work and requires equivalent freedoms in derivative versions.
Copywriting means writing advertising or promotional text, while copyleft concerns the licensing conditions attached to a work.