FAQFrequently asked questions about PaperStack — data, API, billing, and technical details.FAQ General What is PaperStack?Who is PaperStack for?Is there a free tier? Data How is the data sourced?What schema version do you use?How often is data updated?What exams are covered?What question types are supported?Are diagrams included?How do I verify data integrity?Can I request specific exams or years? API What is the base URL?What authentication is required?What format is the response?What HTTP methods are supported?Is there a rate limit?What happens if I exceed the rate limit?What is the difference between paper.json and subject files? Billing Is PaperStack free?Will there be paid plans?Will existing free users be affected? Technical Can I use PaperStack in production?What is the uptime guarantee?How do I get help?Errors & TroubleshootingHTTP status codes, error responses, and solutions for the PaperStack API.