How Do They Make Money?

Advertising. Of their total revenue, (91%) in 2024 and (98%) in 2023 was from third parties advertising on their platform.

Everything else is just lumped together as other revenue in their income statement, but from what I gather, they also make money from:

Content licensing for purposes including machine learning, business analysis, display, and training generative AI models (Reddit's suing Anthropic for training their AI model without permission)
Reddit’s earnings programs for contributors, developers, and creators, while also providing a source of revenue for Reddit as well