Thursday's expansion is the latest move to underscore the growing importance of Twitter's short posts, or "tweets," to Internet search engines. Both Google and Microsoft are paying Twitter for better access to the millions of tweets shared each day.
Yahoo, based in Sunnyvale, Calif., is relying on free tools to find tweets that touch upon a topic mentioned in a search request. A link to the relevant tweets will appear among the rest of Yahoo's search results.
Yahoo last month began to include tweets as part of a feature that identifies hot news stories.