As of 2015, latest episodes of Castle are accessible for free, the day after they are aired, on Hulu Plus and WATCH ABC. To watch the latest episodes of "Castle" on WATCH ABC, one must subscribe to any of the TV providers listed on ABCs website.
WATCH ABC is an app that works on numerous devices including computers, tablets and smartphones. Viewers can watch the programs on the network live or full episodes of aired programs on the go or anytime they want.
To watch the most recent episodes or live programs, viewers must sign in with a TV provider account. Episodes that require a sign in appear with a Key Symbol and Verify to Watch label. TV providers are the companies that viewers pay to get television service. The restrictions are only for the most recently aired episodes, while older episodes are available without signing in.
Hulu is a streaming service that offers the content from the current season of TV shows from five of the six largest U.S. broadcasters. It is a paid subscription service that allows subscribers to watch the latest episodes of numerous TV shows, including "Castle," for free.
Websites such as Sidereel.com and TV.com list links to numerous sources, both paid and free (if available), where "Castle" episodes are available for viewing.