CC BY-SA (Attribution-ShareAlike)¶
CC BY-SA is the copyleft Creative Commons license. Like CC BY, it allows free use with attribution. The addition of ShareAlike requires that derivatives use the same (or compatible) license.
At a Glance¶
| Attribute | Value |
|---|---|
| SPDX Identifier | CC-BY-SA-4.0 |
| Type | Copyleft |
| Free Culture | Yes |
| Attribution Required | Yes |
| ShareAlike Required | Yes |
What It Allows¶
- Commercial use
- Modification and adaptation
- Distribution
- Private use
- Any format or medium
What It Requires¶
- Give appropriate credit
- Provide a link to the license
- Indicate if changes were made
- License derivatives under CC BY-SA or compatible
- Not add additional restrictions
What It Prohibits¶
- Sublicensing under incompatible terms
- Applying additional legal restrictions
- Implying creator endorsement
ShareAlike Explained¶
The ShareAlike clause means:
If you create a derivative work, you must license your contributions under the same terms. This is "copyleft" for creative works—ensuring that openness propagates.
What counts as a derivative?¶
| Action | Derivative? | ShareAlike applies? |
|---|---|---|
| Verbatim copying | No | Just follow CC BY-SA |
| Translation | Yes | Must be CC BY-SA |
| Adapting for new context | Yes | Must be CC BY-SA |
| Collecting in anthology | Usually no | Original stays CC BY-SA, your additions can differ |
| Remixing or mashup | Yes | Must be CC BY-SA |
Collections vs Derivatives¶
A collection (anthology, compilation) where works remain separate doesn't trigger ShareAlike. The individual works keep their licenses, and your selection/arrangement can be separately licensed.
But if you integrate the work into something new (derivative), ShareAlike applies to the whole.
Compatible Licenses¶
CC BY-SA 4.0 can be one-way compatible with other copyleft licenses. Creative Commons maintains a list of compatible licenses—currently including:
- CC BY-SA 4.0 International
- Free Art License 1.3
- GPL v3 (for appropriate content)
This means you could incorporate CC BY-SA work into a GPL v3 project, but the result would be GPL v3 (not CC BY-SA).
CC BY-SA vs GPL¶
Both are copyleft, but for different domains:
| Aspect | CC BY-SA | GPL |
|---|---|---|
| Designed for | Creative works | Software |
| Source code | Not a concept | Required |
| Patent provisions | None | Yes (v3) |
| Modification disclosure | "Indicate changes" | Mark modified files |
| Compatibility | GPL v3 (one-way) | Not with CC BY-SA |
Private Use Exception¶
ShareAlike only applies when you share your adaptation. You can:
- Create private adaptations
- Modify for personal use
- Use internally in an organization
Without sharing publicly, no ShareAlike obligations kick in.
CC BY-NC-SA¶
Adding NonCommercial to ShareAlike creates CC BY-NC-SA:
| Attribute | Value |
|---|---|
| SPDX Identifier | CC-BY-NC-SA-4.0 |
| Free Culture | No (NC restriction) |
This is popular for educational content where creators want:
- Open sharing among educators
- Adaptations to remain open
- Commercial publishers to need separate licenses
When to Choose CC BY-SA¶
CC BY-SA is appropriate when:
- You want derivatives to stay open
- You believe in "share alike" philosophy
- Commercial use is fine if sharing continues
- You're building a commons (like Wikipedia)
When to Choose Something Else¶
- Don't care if derivatives close → CC BY
- Want to block commercial use → CC BY-NC-SA
- Want maximum freedom → CC0
- For software → Use GPL, not CC BY-SA
Notable Works Under CC BY-SA¶
- Wikipedia (all content)
- OpenStreetMap data (until 2012, then ODbL)
- Stack Overflow content (answers and questions)
- Many textbooks and OER (Open Educational Resources)