The Reddit API is a content API: an OAuth app, per-client rate limits, and endpoints for posts, comments, and subreddit metadata. It can answer "what is in r/X" right now. It cannot answer "how fast is r/X growing" without polling, storage, and a normalization layer you build yourself. Trends API covers the trend job: reddit as a keyword source returns subreddit subscriber growth as a normalized 0-100 series, and Reddit Hot Posts is a live board. Request shape is on the API reference.
What the Reddit API is shaped for
The official API is built for apps that read and write Reddit: bots, mod tools, clients. Access runs through an OAuth app, and data access sits behind Reddit's current terms and tiers. For a trend question the relevant object is subreddit metadata, which returns a current subscriber count. A count is a snapshot. History means polling every subreddit on a schedule and storing the deltas.
Subreddit growth as one call
POST https://api.trendsapi.ai/api
Authorization: Bearer <api_key>
Content-Type: application/json
{"mode":"get_growth","source":"reddit","keyword":"LocalLLaMA","percent_growth":["14D"]}
The keyword is the subreddit name with no r/ prefix. A live pull on 2026-09-20 for LocalLLaMA returned 14D score growth of +1645 percent (34.9 recent against 2.0 baseline on the 0-100 scale), with subscriber volume up 36.72 percent over the same window. body is a JSON string and must be parsed a second time.
The live board without the listing crawl
get_top_trends with type Reddit Hot Posts returns the current front-page ranking, and Reddit World News covers r/worldnews. No keyword, no listing pagination. Feed strings are on the live feeds reference. The endpoint-by-endpoint version of this page is Reddit trends without the Reddit API.
When the official API is the right tool
Keep the Reddit API when the product posts, moderates, or reads specific threads. Switch when the question is growth, ranking, or comparison against search and social on one scale. Reddit's current pricing is on its developer site; Trends API caps sit on pricing. The cross-platform walkthrough is social listening.