Unity3D: How to Post to Facebook from your Unity Game

We've shown you a simple way to post to Twitter from within your game; today, we're going to tackle a simple way to post to Facebook. The general idea is the same, but there's a little more setup involved. I'm going to supply a template that will work out of the box, and we'll talk about the specifics afterwards.

Before you get cracking in your code, you're going to need to create a Facebook app to handle sharing from your game. Start by going here to create your app.

Once your app is ready, we're going to use it to publish to Facebook. Much like Twitter, we're going to use Application.OpenURL to send the request to Facebook and let them make the magic happen.

If you've read my other posts, you'll know that I'm a big fan of using NGUI for buttons and the like. If you're not using it, I've written a very simple post on getting started with it. With NGUI, just call the ShareToFacebook () method in the OnClick () method of the button of your choice, passing in the proper parameters.

You may have stumbled across similar code, but nearly all of the examples I've found were forming the URL improperly. Here's what I have, and it works wonderfully:

private const string FACEBOOK_APP_ID = "123456789000";
private const string FACEBOOK_URL = "http://www.facebook.com/dialog/feed";
 
void ShareToFacebook (string linkParameter, string nameParameter, string captionParameter, string descriptionParameter, string pictureParameter, string redirectParameter)
{
Application.OpenURL (FACEBOOK_URL + "?app_id=" + FACEBOOK_APP_ID +
"&link=" + WWW.EscapeURL(linkParameter) +
"&name=" + WWW.EscapeURL(nameParameter) +
"&caption=" + WWW.EscapeURL(captionParameter) + 
"&description=" + WWW.EscapeURL(descriptionParameter) + 
"&picture=" + WWW.EscapeURL(pictureParameter) + 
"&redirect_uri=" + WWW.EscapeURL(redirectParameter));
}

If you've followed our Twitter post, you can see that there is a little more to this. The FACEBOOK_APP_ID comes from the app that you built (I've used a fake one here, so remember to replace it with yours). The FACEBOOK_URL is the URL used for posting to the feed. After that, we get to the meat and potatoes of customizing our content.

linkParameter is the link that will be posted to the wall. For example, you could link to your game's website or download page.

nameParameter is the title of your post. You probably want to briefly describe what it is you're posting (i.e., "I'm playing Game XYZ!"). The name will be a link to the URL described by linkParameter.

captionParameter is the caption of your post. This appears in small type right below the title of your post. It may be a good idea here to give a bit more detail on what you're posting (for example, "New high score!"). 

descriptionParameter is the body of the message. Here, you can give the bulk of your message, such as the score you attained, an achievement you unlocked, etc. 

pictureParameter is a link to a picture you'd like to include in your post. Keep in mind that pictures must be at least 200px x 200px.

Finally, redirectURIParameter is the page the user will be redirected to after publishing their message. This is the parameter that is likeliest to cause you a headache. If you want to go the no-hassle route, just link to http://www.facebook.com/.

Improperly forming your URL or trying to redirect to a domain that is not assigned to your Facebook app are almost always the cause of error 100 and error 191. If you experience either of these, ensure that your URL is being formed correctly by comparing it to the URL redirection example on this page.

If you want to redirect to a page that is outside of Facebook's domain, you'll need to take a couple of extra steps. First, go to your app's page, and select "Settings" from the menu on the left. Click the "Add Platform" button, and select "Website". Under "Site URL", enter the page you want to associate with your app. Now, under "App Domains", enter the domain that page belongs to. So, if you added your Site URL as "www.example.com/index.html", you'll want to enter "www.example.com" under App Domains. Now, your redirect should work as intended.

If you'd like to go more in-depth, you can view the Feed Dialog documentation here. Keep in mind that you can use the Share Dialog, as the Feed Dialog is deprecated, but we're going for simplicity here, and I think this is the quickest and easiest way to get Facebook sharing going.