FB Apprequests: How many friends can I invite at a time?

Question

I have a "friendpicker" on my app to send an apprequest. It features an option "Select All", so.. when I try to invite 560 friends it doesen't work. Their user ID's don't even fit in the URL.

So, is there any fixed limit for this feature?

I couldn't find any reference to it in the documentation (https://developers.facebook.com/docs/concepts/requests/)

Answer 1

In https://developers.facebook.com/docs/reference/dialogs/requests/ I found the following information regarding the to parameter:

If not (set), the sender will see a multi-friend selector and will be able to select a maximum of 50 recipients.

So, I did a test populating to with 51 and 50 friends. The first gave an explicit error (too much friends) and the second actually passed.

TL;DR

The limit is 50 friends.

Answer 2

Facebook limit is 50, Internet Explorer limitation only supports up to 25 requests at one time

A user ID or username, or a comma-separated list of them. These may or may not be a friend of the sender. If this is specified by the app, the sender will not have a choice of recipients. If not, the sender will see a multi-friend selector and will be able to select a maximum of 50 recipients. (Due to URL length restrictions, the maximum number of recipients is 25 in IE7/IE8 when using a non-iframe dialog.)

https://developers.facebook.com/docs/reference/dialogs/requests/

To simplify the process trigger the process of suggesting the invite right after page load, and don't fill in the "to"... this will open up a facebook dialog that allows facebook to handle the ui and processing of the request.

Example shown below

<script src="http://connect.facebook.net/en_US/all.js#xfbml=1"> </script>
<script type="text/javascript">
    FB.init({ 
        appId:'<? echo $appID; ?>', cookie:true, 
        status:true, xfbml:true 
    });
    function send_invitation(){
        FB.ui({ 
            method: 'apprequests', 
            message: 'ReeMatch analyzes your resume to find you jobs and compare them to bring you relevant jobs instantly. - www.ReeMatch.com',
            redirect_uri: 'http://reematch.com/',
            max_recipients: 25,
            title: "Invite your friends to ReeMatch.com"
        });
    }
    function fb_logout(){
        FB.logout(function(response) {
              parent.location ='<? echo $base_url; ?>';
        });
    }
    setTimeout(function () {
        send_invitation();
    }, 1000);
</script>

FYI: We put a 1 second timer so when it triggers the send_invite call the browser doesn't block the call.

Answer 3

At the bottom of that page you linked, there's a banner that says

New Facebook policy, effective July 10, 2013: App requests can no longer offer a select all option or pre-select multiple recipients to receive a request.