Credits and licences
This site is built on open-source software. Thank you to the people who make it.
| Component | Used for | Licence |
|---|---|---|
| Ketcher 3.18.0, EPAM Systems | The structure drawing editor | Apache 2.0 |
| Indigo (indigo-ketcher), EPAM Systems | Chemistry functions inside the editor | Apache 2.0 |
| RDKit / RDKit.js 2026.9.1 | Checking answers and drawing structures on this site | BSD 3-Clause |
| React | Interactive page components | MIT |
| Astro | Building the static website | MIT |
The full licence and notice texts of every third-party package shipped with this site are inthird-party-licenses.txt.
Data used on the free-drawing page
Names on the free-drawing page come from PubChem (National Center for Biotechnology Information, US National Library of Medicine) for structures that are not among this site's exercises. Each name is shown with a link to its PubChem record.
Tools and data used to check the exercises
These are used when preparing exercises and are not part of the website:
- OPSIN (Open Parser for Systematic IUPAC Nomenclature), Daniel Lowe, MIT licence: interprets each exercise name independently so it can be compared with the answer structure.
- PubChem, National Center for Biotechnology Information: each exercise name is looked up and its recorded structure compared with the answer.
The exercises, hints, explanations and guides on this site are original content written for this site.