Is there a difference between Facebook's Open Graph API and its Graph API?

Question

Is there a difference between Facebook's Open Graph API and its Graph API?

Answer 1

Yes, there is a huge difference between the both. Graph API, quoting from the documentation

The Graph API is the primary way to get data in and out of Facebook's social graph. It's a low-level HTTP-based API that you can use to query data, post new stories, create check-ins or any of the other tasks that an app might need to do.Most other APIs at Facebook are based on the Graph API.

In short Graph API provides the API that make the core of any Facebook application. Whereas the Open Graph API is provided by Facebook so that apps can create custom objects (like Book, Music or other real world objects as per requirement) and the actions that can be performed on them (like reading, listening). Having this makes Facebook and the application more engaging. Quoting from the documentation,

The Open Graph lets apps tell stories on Facebook through a structured, strongly typed API. People use stories to share the things they're doing, the people they're doing them with and the places where they happen. Open Graph lets you integrate apps deeply into the Facebook experience, which increases engagement, distribution and growth.

Also, the relation between the two can be summarized as

Facebook's Open Graph allows you to define new objects and actions in a user's social graph, and the way that you create new instances of those actions and objects is via the Graph API.

Answer 2

The Facebook documentation makes it sound like Open Graph is a completely different animal from the Graph API, but Open Graph really seems to be an extension of Graph API. Your API calls all end up going to graph.facebook.com if that's any indication. Their API endpoints share similar syntaxes and are governed by the same access rules. What you'll be allowed to do with either depends on the permissions dictated in the access token.

While Graph API and Open Graph work in different ways and touch different things, it's not an "either or" kind of scenario where you need to make decision if I'm only going to use Graph API or Open Graph. You'll probably end up using both or just using Graph API.

You can think of Graph API as the part of the API that does the "traditional Facebooky things". If you just wanted to post something like a simple status update, just use Graph API to send something to //feed. If you want to create more complex timeline messages that hold uniquely typed data that you define, use Open Graph. For example, you're a birder and you want to post an update to say you saw a certain bird and you wanted to display the species, color, and size of the bird as attributes in your custom object.

The biggest difference between Graph API and Open Graph from a usage standpoint is in the way you can pass the data that Facebook needs to build the objects you want. In Graph API, you post the data you want to pass into Facebook. In Open Graph, you can either post the data or you can feed it a URI pointing to the location of the resource that you want Facebook to scrape for content from RDF metadata tags.

So yeah, they have their differences, but they're also closely related.