Sources panel overview

Use the Chrome DevTools Sources panel to:

• View files.
• Edit CSS and JavaScript.
• Create and save Snippets of JavaScript, which you can run on any page. Snippets are similar to bookmarklets.
• Debug JavaScript.
• Set up a Workspace, so that changes you make in DevTools get saved to the code on your file system.

View files #

Use the Page pane to view all of the resources that the page has loaded.

Figure 1. The Page pane

How the Page pane is organized:

• The top-level, such as top in Figure 1, represents an HTML frame. You'll find top on every page that you visit. top represents the main document frame.
• The second-level, such as developers.google.com in Figure 1, represents an origin.
• The third-level, fourth-level, and so on, represent directories and resources that were loaded from that origin. For example, in Figure 1 the full path to the resource devsite-googler-button is developers.google.com/_static/19aa27122b/css/devsite-googler-button

Click a file in the Page pane to view its contents in the Editor pane. You can view any type of file. For images, you see a preview of the image.

Figure 2. Viewing the contents of jquery-bundle.js in the Editor pane

Edit CSS and JavaScript #

Use the Editor pane to edit CSS and JavaScript. DevTools updates the page to run your new code. For example, if you edit the background-color of an element, you'll see that change take effect immediately.

Figure 3. Editing CSS in the Editor pane to change the background color of an element from blue to red

CSS changes take effect immediately, no save needed. For JavaScript changes to take effect, press Command+S (Mac) or Control+S (Windows, Linux). DevTools doesn't re-run a script, so the only JavaScript changes that take effect are those that you make inside of functions. For example, in Figure 4 note how console.log('A') doesn't run, whereas console.log('B') does. If DevTools re-ran the entire script after making the change, then the text A would have been logged to the Console.

Figure 4. Editing JavaScript in the Editor pane

DevTools erases your CSS and JavaScript changes when you reload the page. See Set up a Workspace to learn how to save the changes to your file system.

Create, save, and run Snippets #

Snippets are scripts which you can run on any page. Imagine that you repeatedly type out the following code in the Console, in order to insert the jQuery library into a page, so that you can run jQuery commands from the Console:

let script = document.createElement('script');
script.src = 'https://code.jquery.com/jquery-3.2.1.min.js';
script.crossOrigin = 'anonymous';
script.integrity = 'sha256-hwg4gsxgFZhOsEEamdOYGBf13FyQuiTwlAQgxVSNgt4=';
document.head.appendChild(script);

Instead, you can save this code in a Snippet and run it with a couple of button clicks, any time you need it. DevTools saves the Snippet to your file system.

Figure 5. A Snippet that inserts the jQuery library into a page

To run a Snippet:

• Open the file via the Snippets pane, and click Run .
• Open the Command Menu, delete the > character, type !, type the name of your Snippet, then press Enter.

See Run Snippets Of Code From Any Page to learn more.

Debug JavaScript #

Rather than using console.log() to infer where your JavaScript is going wrong, consider using the Chrome DevTools debugging tools, instead. The general idea is to set a breakpoint, which is an intentional stopping place in your code, and then step through your code's execution, one line at a time. As you step through the code, you can view and change the values of all currently-defined properties and variables, run JavaScript in the Console, and more.

See Get Started With Debugging JavaScript to learn the basics of debugging in DevTools.

Figure 6. Debugging JavaScript

Set up a Workspace #

By default, when you edit a file in the Sources panel, those changes are lost when you reload the page. Workspaces enable you to save the changes that you make in DevTools to your file system. Essentially, this lets you use DevTools as your code editor.

See Edit Files With Workspaces to get started.