SerpApi documents a Google Trends Results API at GET https://serpapi.com/search?engine=google_trends. That call mirrors Explore: interest over time, interest by region, related topics, related queries. A second engine, google_trends_trending_now, scrapes the Trending Now page and requires geo. Trends API is POST https://api.trendsapi.ai/api with mode, source, and a keyword. body is a JSON string and must be parsed a second time. Field names: the API reference. Plan text: pricing. Google notes: the Google Trends guide.
GET engine google_trends versus POST /api
SerpApi query params include q (up to five terms on TIMESERIES), data_type (TIMESERIES, GEO_MAP, GEO_MAP_0, RELATED_TOPICS, RELATED_QUERIES), geo, hl, tz, cat, gprop, and date strings such as today 12-m. Auth is api_key. Cached identical searches are free for one hour.
POST https://api.trendsapi.ai/api
Authorization: Bearer <api_key>
Content-Type: application/json
{"mode":"get_time_series","source":"google search","keyword":"coffee"}
No engine. No data_type. source google search is web interest. YouTube is a new POST with source youtube, not gprop=youtube on the same call.
Related queries and geo maps SerpApi keeps
Those widgets are the reason to keep SerpApi in a stack that already uses it for Search, Maps, or Shopping. Trends API does not ship a rising/top related-queries split and does not ship DMA or CITY maps. Do not invent those fields on the inner payload.
Sources SerpApi does not return
tiktok, amazon, reddit, npm, python, steam, wikipedia, app downloads, and app rankings are Trends API source strings. They are not SerpApi gprop values. gprop stays inside Google (images, news, froogle, youtube).
Billing unit: a search versus a 200
SerpApi counts a successful Trends search against the monthly search allotment. Trends API counts a successful 200. Do not quote this product's caps here. Read pricing. Read SerpApi pricing for the current search table.