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How do I look up a subreddit by name?
Call GET /v1/reddit/subreddits with a subreddit query param (Reddit's exact casing, r/ prefix optional) or a url. Read data.lookupStatus, then data.subreddit (description, rules, iconUrl, bannerUrl, advertiserCategory) and data.metrics (subscribers, weeklyActiveUsers, weeklyContributions).
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This answer comes from Reddit data API, which covers the full detail, endpoints and pricing in credits.