Update (June 23, 2014):
Good news, Downton Abbey fans! Season 4 is officially available on Amazon Prime Instant Video, reports PC Magazine. The exclusive content licensing agreement Amazon scored with PBS last year means this will be your main outlet for post-TV viewing through at least Season 5. Prime's also the only online source with all four season available. Sorry Netflix and Hulu Plus.
Original story (August 22, 2013):
Gotta get some early 20th-century period drama into your life? Understandable. Whether you’re one of the lucky viewers in the UK who got to start watching Downton Abbey Season 4 in September or just joined in with the US premiere on January 5, 2014, we could all use a little more Downton. So where can you watch online? It depends on what you’re looking for.
I want to watch Season 4. For American readers, you can watch each episode after it premieres on PBS thanks to the helpful people over on that channel’s website. This won’t give you a look ahead at episodes (legal ways to do that are few and far between outside the United Kingdom) but PBS.com will allow you to catch up or re-watch Season 4 as aired to date.
If you do live in the UK, there are plenty of options on how you can get your weekly dose o' Downton. When in season, the show airs live on ITV at 9 p.m. Sundays and also online at ITV. If you miss it night of, never fear. ITV kindly uploads the episode to its ITV Player, which is where you can now re-watch Season 4.
I want to marathon Seasons 1 through 3. Amazon Prime Instant Video and iTunes have you covered. Right now, both offer Seasons 1, 2, and 3 on their respective sites. You can also watch Season 3 Episode 7 over on PBS until the fourth installment starts on January 5. Once we would have also suggested heading on over to Netflix or Hulu, but in 2012 both announced plans to pull the show from their line-ups.
Excuse me?! Explain. Back in February 2013, Amazon signed a content licensing agreement with PBS Distribution that gave the mega-site exclusive streaming rights to Downton. That includes Season 4 and likely Season 5. As such, PC Magazine reports that “beginning on an unknown future date, [Amazon] Prime Instant Video will be the only digital subscription service from which viewers can stream the show.”
Upside: Prime offers customers a 30-day free trial.