The best web search APIs for developers are Bing Web Search, Google Search API, and Custom Search API, according to this article. These three APIs have the highest popularity scores of 8.7/10, 9.8/10, and 9.3/10 respectively. They offer robust search capabilities and can be used to create powerful search experiences for users across various platforms. Bing Web Search is best for making web searches that need filtering, Google Search API is best for searching web pages and images, and Custom Search API is best for creating customized web and image searches.