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chrome/common/extensions/docs/templates/articles/manifest/externally_connectable.html

 <h1>externally_connectable</h1>
 
 <p>
 The <code>externally_connectable</code> manifest property declares which extensions, apps, and web pages can connect to your {{platform}} via <a href="../runtime#method-connect">runtime.connect</a> and <a href="../runtime#method-sendMessage">runtime.sendMessage</a>.
 </p>
 
 <p>
 For a tutorial on message passing see <a href="../messaging#external">cross-extension and app messaging</a> and <a href="../messaging#external-webpage">sending messages from web pages</a>.
 </p>
 
 <h2 id="without-externally-connectable">Connecting without externally_connectable</h2>
 
 <p>
 If <code>externally_connectable</code> is not declared in your {{platform}}'s manifest, all extensions and apps can connect, but no webpages can connect. As a consequence, when updating your manifest to use <code>externally_connectable</code>, if <code>"ids": ["*"]</code> is not specified then other extensions and apps will lose the ability to connect to your {{platform}}. This may be an unintended consequence, so keep it in mind.
 </p>
 
 <h2 id="manifest">Sample manifest.json</h2>
 <pre data-filename="manifest.json">
 {
   "name": "My externally connectable {{platform}}",
   "externally_connectable": {
-    // Extension and app IDs. If this field is not specified, no extensions or
-    // apps can connect.
+    // Extension and app IDs. If this field is not specified, no
+    // extensions or apps can connect.
     "ids": [
       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
       "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
       ...
-      // Alternatively, to match all extensions and apps, specify only "*".
+      // Alternatively, to match all extensions and apps, specify only
+      // "*".
       "*"
     ],
-    // Match patterns for web pages. Does not affect content scripts. If this
-    // field is not specified, no webpages can connect.
+    // Match patterns for web pages. Does not affect content scripts.
+    // If this field is not specified, no webpages can connect.
     "matches": [
       "https://*.google.com/*",
       "*://*.chromium.org/*",
       ...
     ],
-    // Indicates that the extension would like to make use of the TLS channel
-    // ID of the web page connecting to it. The web page must also opt to send
-    // the TLS channel ID to the extension via setting
-    // <code>includeTlsChannelId</code> to <code>true</code> in
-    // $(ref:runtime.connect)'s connectInfo or $(ref:runtime.sendMessage)'s options.
+    // Indicates that the extension would like to make use of the TLS
+    // channel ID of the web page connecting to it. The web page must
+    // also opt to send the TLS channel ID to the extension via setting
+    // <code>includeTlsChannelId</code> to <code>true</code> in $(ref:runtime.connect)'s connectInfo
+    // or $(ref:runtime.sendMessage)'s options.
     "accepts_tls_channel_id": false
   },
   ...
 }
 </pre>
 
 <h2 id="reference">Reference</h2>
 <p class="api_reference">
-{{+partials.type type:data/}}
+The externally_connectable manifest key can have the following properties:
+{{+partials.manifest_type type:data/}}
 </p>