Which Creative Commons licence should I choose?

Pick CC BY 4.0 unless you have a concrete reason to block commercial use, to force ShareAlike, or to prohibit sharing of adaptations. The decision tree has exactly two branches: do you want to permit commercial reuse, and must derivatives carry the same license? That is it. Strip it back. Confirm you own the rights to everything in the work, then apply the most permissive license you are comfortable with. You can dual-license later but you cannot revoke rights under a license already granted. The three decision points below explain the trade-offs at each one using official Creative Commons terms, version 4.0.

Allow Commercial Reuse?

Start with one question: do you want to allow commercial reuse? If your answer is yes, you remove the NC licenses. If your answer is no, your choice narrows to CC BY-NC 4.0, CC BY-NC-SA 4.0, or CC BY-NC-ND 4.0. The NonCommercial condition in version 4.0 defines commercial advantage or monetary compensation as the primary intent. The type of organisation using your work does not decide the issue. A nonprofit running a paid workshop may be commercial; a small business using your photo in a free tutorial may not be. There is no bright-line rule. If the risk of for-profit exploitation bothers you, pick NC.

Allow Shared Adaptations?

Second question: do you want to allow adaptations to be shared? If yes, you keep BY, BY-SA, BY-NC, or BY-NC-SA. If no, your choice is BY-ND or BY-NC-ND. Under NoDerivatives, a reuser may make a private adaptation but may not share it. Translation is normally an adaptation. Synchronising music with a moving image is expressly Adapted Material under 4.0. Whether cropping, excerpting, editing or combining creates an adaptation depends on your jurisdiction's copyright law. There is no universal boundary. For most creators, ND is the simplest restriction to enforce because the rule is binary: sharing a changed version is not allowed.

Require ShareAlike?

Third question: if you allow adaptations, do they have to carry the same license? Yes means ShareAlike. No means BY or BY-NC. ShareAlike is triggered only when Adapted Material is shared, not when unchanged material sits beside other works in a collection. The adapter must license their contribution under BY-SA 4.0 or an officially designated compatible license. The official compatibility list controls this. As of version 4.0, Creative Commons lists one-way compatibility from BY-SA 4.0 to GPLv3 for adapted material. That does not create reverse compatibility. Do not assume two SA licenses are compatible. If your goal is a growing commons where improvements stay open, SA is your tool.

Reach

CC BY 4.0 has the widest reach. Anyone can use your work for business or non-business purposes, adapt it, and share adaptations under any terms. CC BY-ND 4.0 allows wide sharing but blocks shared adaptations, which reduces the work's value as building material for remixes, educational resources, or collaborative projects. CC BY-NC 4.0 narrows reach to non-commercial contexts only. That may exclude business reuse you want but also may protect you from uses you dislike.

Compatibility

Compatibility matters when your work will be combined with others. CC BY 4.0 does not impose ShareAlike on an adaptation, but every other input and the proposed adapter terms still need separate compatibility checks. A work under CC BY-SA 4.0 can only be combined with works under a compatible license, and the result must be licensed under BY-SA 4.0. The official compatibility list is short. A work under CC BY-ND 4.0 cannot be part of a shared adaptation at all. The same logic applies to NC licenses: mixing a BY-NC work with a BY work for business use is not allowed under the NC license. Plan for the worst case. If your work might be part of a large collaborative project, BY or BY-SA are the only safe choices.

Reversibility

Creative Commons licenses are irrevocable. Once you apply a license and someone receives the work while complying with its terms, you cannot take that permission back. You can stop distributing the work or offer it under other terms to new users, but everyone who already has a copy under the old license keeps that license. Dual licensing is permitted. You can release a work under CC BY 4.0 and also sell a separate commercial license. The irrevocability means the most permissive license you apply is the one that sticks. Start from the most permissive you can tolerate, not the most restrictive you can imagine.

Only the copyright holder or someone with express authority may apply a Creative Commons license. Confirm joint authorship, employment ownership, commissioned-work terms, performer rights, samples, and third-party inclusions before you add a license notice. If you are not the sole rights holder, do not apply a CC license until everyone agrees. The official Creative Commons chooser builds a license notice for you. It does not validate ownership. No registration with Creative Commons is required.

Your license notice must identify the work, name the creator, name and link the exact license and version, link the source where useful, and clearly exclude any content not covered. Use version 4.0 for a new license unless you have a specific, informed reason to use an older release or a jurisdiction-specific port. After version 4.0, Creative Commons stopped publishing ports; 4.0 is the international release. A license already attached to someone else's work cannot be unilaterally upgraded by a reuser.

Do not apply a CC license to software code. Use a recognised free or open-source software license for code. Documentation, art and other non-code assets may carry separate CC licenses if they are clearly marked. Do not apply a CC license to a trademark as though it granted trademark permission, to content you do not control, or to a work meant to remain confidential. If you have questions about ownership, get legal advice before you publish.

Before you choose any Creative Commons license, confirm you own the rights to every element in your work. This is the step that most often goes wrong. If you incorporate a photo, a sample, a font, or a clip that you did not create, you need permission from that rights holder. If you are uncertain, do not apply a CC license. Get separate permission or use only material you control. Once you have confirmed ownership, apply the most permissive license you are comfortable with. That gives you the widest reach and the fewest compatibility problems downstream. You can always dual-license later if you need to grant business permission to a specific user. The irrevocability of the public license means you should not start from the most restrictive option and hope to loosen it later.