Ahrefs’ main source of discovering new pages is the:

The correct answer is Crawler. Ahrefs, like other search engines and SEO tools, uses a crawler (often called a spider or bot) to systematically browse the internet, follow links, and discover new web pages and updated content. This process is how Ahrefs builds its extensive database of backlinks, keywords, and site audit data. The 'Scheduler' is not a component for discovering pages; it might be used internally for timing crawls but doesn't perform the discovery itself. The 'Indexer' is responsible for processing and storing the information gathered by the crawler, making it searchable and analyzable, but it doesn't discover the pages initially. Therefore, the crawler is the primary mechanism for finding new pages.