Use chrome.devtools.inspectedWindow to interact with the inspected window: obtain the tab ID for the inspected page, evaluate the code in the context of inspected window, reload the page, or obtain the list of resources within the page.

See DevTools APIs summary for general introduction to using Developer Tools APIs.

Overview

The tabId property provides the tab identifier that you can use with the chrome.tabs.* API calls. However, please note that chrome.tabs.* API is not exposed to the Developer Tools extension pages due to security considerations — you will need to pass the tab ID to the background page and invoke the chrome.tabs.* API functions from there.

The eval() method provides the ability for extensions to execute JavaScript code in the context of the main frame of the inspected page. This method is powerful when used in the right context and dangerous when used inappropriately. Use the chrome.tabs.executeScript() method unless you need the specific functionality that the eval() method provides.

Here are the main differences between the eval() and chrome.tabs.executeScript() methods:

• The eval() method does not use an isolated world for the code being evaluated, so the JavaScript state of the inspected window is accessible to the code. Use this method when access to the JavaScript state of the inspected page is required.
• The execution context of the code being evaluated includes the Developer Tools console API. For example, the code can use inspect() and $0.
• The evaluated code may return a value that is passed to the extension callback. The returned value has to be a valid JSON object (it may contain only primitive JavaScript types and acyclic references to other JSON objects). Please observe extra care while processing the data received from the inspected page — the execution context is essentially controlled by the inspected page; a malicious page may affect the data being returned to the extension.

Important: Due to the security considerations explained above, the chrome.tabs.executeScript() method is the preferred way for an extension to access DOM data of the inspected page in cases where the access to JavaScript state of the inspected page is not required.

The reload() method may be used to reload the inspected page. Additionally, the caller can specify an override for the user agent string, a script that will be injected early upon page load, and an option to force reload of cached resources.

Use the getResources() call and the onResourceContent event to obtain the list of resources (documents, stylesheets, scripts, images etc) within the inspected page. The getContent() and setContent() methods of the Resource class along with the onResourceContentCommitted event may be used to support modification of the resource content, for example, by an external editor.

Examples

The following code checks for the version of jQuery used by the inspected page:

chrome.devtools.inspectedWindow.eval(
    "jQuery.fn.jquery",
     function(result, isException) {
       if (isException)
         console.log("the page is not using jQuery");
       else
         console.log("The page is using jQuery v" + result);
     }
);

You can find more examples that use Developer Tools APIs in Samples.