Before using a dataset, check its licence. Being able to download data doesn't mean you can use it any way you like.
Common Licences
| Licence | In practice |
|---|---|
| Public domain / CC0 | No conditions; use freely |
| CC BY 4.0 | Any use, including commercial, with attribution |
| CC BY-SA 4.0 | As CC BY, and adaptations you share must use the same licence |
| ODbL | Open Database Licence: attribution and share-alike for databases |
| CC BY-NC | Non-commercial use only |
| Custom terms | Read carefully; may restrict use or redistribution |
Many government datasets use their own open licences, often similar to CC BY.
Attribution
Licences requiring attribution usually expect the creator's name, the dataset title, a link to the source and the licence. Dataset cards often give a preferred citation.
Share-Alike
Share-alike licences apply to adaptations you distribute — combined datasets, for example. Think about this before mixing share-alike data into a product.
Non-Commercial Restrictions
"Non-commercial" can be ambiguous. If there's any doubt about whether your use counts, ask the publisher.
No Licence Means No Permission
Absence of a licence doesn't make data free to use. Contact the owner.
Personal Data
A licence covers copyright and database rights; it doesn't override privacy law. Data about people may carry obligations regardless of its licence.
Keep Records
Log the source, version, licence and attribution for every dataset in your projects. This is general information, not legal advice.