How do you work with related communities instead of competing with them?

The instinct to treat other subreddits covering similar topics as competition is counterproductive. In practice, the Reddit ecosystem functions more like a network of complementary spaces than a zero-sum market. A rising tide of good content and engaged users on one subreddit tends to draw attention to adjacent communities rather than draining them. The practical starting point for building cooperative relationships is to introduce yourself to the moderators of related subreddits through modmail. Explain who you are, describe your community's focus, and express genuine interest in how the two communities might complement each other. Most moderators are volunteers who care about their communities, and a respectful introduction from a fellow moderator is almost always received positively. This initial contact is the foundation for every subsequent form of collaboration. The most common form of cooperation is cross-listing in sidebars or wiki pages. When two subreddits list each other as related communities, members naturally discover both and can participate in whichever one suits a specific post or conversation better. This arrangement is entirely non-exclusive — a member can belong to and participate in both communities simultaneously — and it costs nothing except a sidebar entry. Collaborative events are a stronger form of cooperation. Co-hosting an AMA with a guest relevant to both communities, running a joint contest, or organizing a cross-post week where the best content from each community is highlighted in the other creates shared experiences that build goodwill among members and moderators alike. When content is posted in your community that would be better suited to a related subreddit, redirect the poster helpfully rather than just removing the post. Saying "This question would be a great fit for r/[related community], which specializes in exactly this" is a service to both the user and the other community. Over time, this kind of thoughtful cross-referral builds a reputation for your community as a trustworthy participant in the broader ecosystem rather than an insular space that ignores everything outside its own boundaries.