Choose your experience
Free vs Support
All learning content is free, always. The Support tier adds a personal AI tutor and official certification.
Common questions
Is the course content really free?
Yes. All 64 learning units, video lectures, exercises, quizzes, and community responses are free and always will be. SiD is open source.
Who is Carl?
Carl is your AI tutor, inspired by Carl Sagan's curious and engaging teaching style. He gives personalized feedback on your exercises and engages you in Socratic dialogue to deepen your understanding.
What does the certificate require?
With Support tier, Carl grades every exercise response on a 0 to 100 scale. You need an average score of 80% or higher across all exercises in a learning path to earn your certificate. You can re-submit answers to improve your score. If you started on the free tier, you will need to reset your exercise progress so Carl can grade each response fresh.
Have a code?
If your organization or university provided a license code, redeem it here.
Is this a subscription?
No. It is a one-time payment that gives you access for 3 or 12 months. No auto-renewal.
Can I get Support tier through a donation?
Yes. Any donation of €20 or more automatically unlocks Support tier (3 months for €20+, 12 months for €45+). The buttons above and the donation page both work.
Where does the money go?
Your payment supports the Except Foundation's mission to keep SiD open and free. It covers AI infrastructure costs and ongoing platform development.