The OpenAI web search API is the web_search tool in OpenAI’s Responses API. You add it to a request, and the model decides when to search the live web, reads the results and answers with inline citations to the pages it used. You don’t need a separate search provider like Tavily, SerpAPI or Firecrawl for basic real-time answers.
I first covered this when OpenAI launched the Responses API in March 2025, when the tool was still called web_search_preview. This guide is updated for the current version: the code below uses web_search, and the sections on domain filters and sources cover options that didn’t exist at launch. The video shows the original version. The ideas are the same, only the tool name and a few options changed.
