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Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

header

An extra named piece of information sent with a request or response.

HTTP headers are name/value pairs carrying metadata such as Content-Type, Authorization and User-Agent.

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