Where to watch Gravity Falls: the legal streaming and home video options
This is a deliberately short guide. There is one place to watch the complete series, and it is the official one.
Streaming
All 40 episodes of Gravity Falls are available on Disney+, which is the only legitimate streaming home for the complete run. Season one originally aired on Disney Channel and season two on Disney XD, but those networks no longer carry the show as a current linear lineup. Availability on Disney+ varies by region, and the service is subscription-based, so you need an active account to watch.
Home video
Shout! Factory released the complete series on DVD and Blu-ray Disc on July 24, 2018, as a seven-disc box set covering all 40 episodes. Two earlier single-disc releases exist for anyone who does not want the full set: Gravity Falls: Six Strange Tales (October 15, 2013, episodes 1 to 6) and Gravity Falls: Even Stranger (August 26, 2014, episodes 7 to 14).
The complete-series box set is the significant one, for two reasons. It is the only commercial release of the unaired 2010 pilot episode, an 11-minute student film in a different art style that Hirsch made at CalArts and that served as the basis for the pitch, and it carries the deleted scenes that were promised as a reward during the Cipher Hunt and released as part of this set. The box set was offered in a Collector's Edition with a bonus disc and is now out of print, so second-hand pricing is the main route to it.
What is not available officially
There is no official standalone release of Gravity Falls on physical or digital media outside Disney's own channels. If a site is offering episode downloads or a "free full season" bundle outside Disney+, it is not an authorised source, and the usual risks of unauthorised streaming apply: malware, fake installers, and credit-card harvesting on "verification" pages. We do not link to any of them.
Related reading and listening
If you want the written version of the world rather than the episodes, the three-book line is covered in our Journal 3, Lost Legends, and Book of Bill guides. Brad Breeck's score is a genuine part of the show's identity and is available through the usual licensed music services rather than from a file-sharing site.
Why the show is still worth watching
The main reference page covers the premise, the production history, and the publication line. If you are starting from episode one, read the episode list with original air dates first so you know the broadcast order, because season two was released irregularly and the intended order is not the same as the "airing" order fans often assume.