<p>GCM allows a maximum of 4 different collapse keys to be used by the GCM server at any given time. In other words, the GCM server can simultaneously store 4 different send-to-sync messages, each with a different collapse key. If you exceed this number GCM will only keep 4 collapse keys, with no guarantees about which ones they will be.</p>
<h3 id="payload">Messages with payload</h3>
<p>Unlike a send-to-sync message, every "message with payload" (non-collapsible message) is delivered. The payload the message contains can be up to 4K. For example, here is a JSON-formatted message in an IM application in which spectators are discussing a sporting event:</p>
<p>Unlike a send-to-sync message, every "message with payload" (non-collapsible message) is delivered. The payload the message contains can be up to 4kb. For example, here is a JSON-formatted message in an IM application in which spectators are discussing a sporting event:</p>
@@ -651,8 +651,8 @@ message sent by the application server. See <a href="adv.html#collapsible">Advan
<tr>
<td><code>data</code></td>
<td>A JSON object whose fields represents the key-value pairs of the message's payload data. If present, the payload data it will be
included in the Intent as application data, with the key being the extra's name. For instance, <code>"data":{"score":"3x1"}</code> would result in an intent extra named <code>score</code> whose value is the string <code>3x1</code>
There is no limit on the number of key/value pairs, though there is a limit on the total size of the message. Optional.</td>
included in the Intent as application data, with the key being the extra's name. For instance, <code>"data":{"score":"3x1"}</code> would result in an intent extra named <code>score</code> whose value is the string <code>3x1</code>.
There is no limit on the number of key/value pairs, though there is a limit on the total size of the message (4kb). Note that the values <em>must be enclosed by strings</em>. If you want to include objects or other non-string data types (such as integers or booleans), you have to do the conversion to string yourself. Optional.</td>
