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Debugging CSS with Chrome DevTools

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Identify and Debug Errors

4:28 with Guil Hernandez

Learn how to identify errors in your CSS, visualize and test element state, and copy or save changes to your CSS from DevTools.

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    In this video, I'll teach you other useful DevTools features that help you 0:00
    quickly identify errors in your CSS; visualize and test hover, 0:04
    active and focus states on elements. 0:08
    Even enabling and disabling classes, and ways to easily copy or 0:10
    save out changes to your CSS. 0:14
    As I mentioned in an earlier video, CSS does not provide you feedback or 0:17
    error messages if your code contains invalid declarations or syntax errors. 0:21
    One of the best features of Chrome DevTools is its ability to 0:26
    quickly recognize errors in your CSS and warn you about them. 0:29
    For example, if I give the h1 a font color of red, we see that 0:33
    it gets crossed out and a warning icon appears to the left of the declaration. 0:40
    Hover over the icon and it displays the text, unknown property name. 0:45
    Well font color is not a valid CSS property, so 0:49
    DevTools immediately flagged it and alerted us. 0:53
    And the same applies to CSS values. 0:56
    So for example, if I set color to reder, 0:58
    it lets me know that I've set an invalid property value. 1:00
    DevTools also provide a simple way to set dynamic 1:08
    pseudo-class selectors on elements like hover, active, and focus. 1:11
    To test the hover styles applied to a button, for 1:17
    example, right-click on the button element in the Elements panel, 1:19
    then select the hover pseudo-class from the menu to enable it. 1:24
    Now another way to toggle element states is by clicking the hov button 1:29
    in the styles pane. 1:33
    This opens a menu that lets you enable and disable element states for 1:35
    the selected element by checking and unchecking the boxes. 1:38
    Now the .cls or 1:42
    element classes button to the right of the toggle element state button, 1:46
    enables another useful feature of Chrome DevTools. 1:50
    Adding, enabling, and disabling CSS classes. 1:54
    When you select an element this panel displays all the CSS classes 1:57
    associated with the selected element. 2:01
    For example, 2:03
    selecting a guest list item shows that the list item has the class guest. 2:04
    Now if I click the confirm check box in the browser for 2:10
    the first guest, it adds the class responded to the list of classes. 2:13
    Now this class is being injected into the class attribute with JavaScript 2:18
    to change the border color. 2:22
    From here you can disable or enable classes by clicking the check boxes. 2:24
    You can even add new classes to the element using the Add new class text 2:30
    field. 2:35
    I like to use this feature when debugging layout problems. 2:41
    For example, add a debug class in my CSS, 2:45
    that applies a two pixel solid red border to an element. 2:49
    Then I can use the class's feature to a apply a temporary red border around 2:57
    a troublesome elements, to help make the document flow easy to understand. 3:01
    For example, select the main element and type the class debug into the field. 3:06
    The class debug is added to the main element's class attributes and 3:13
    we see the red border applied. 3:17
    And I can apply this class to any element to help me isolate the layout problem. 3:19
    So far, we've been testing and editing CSS directly in the styles pane. 3:34
    And like the elements panel, the styles pane does not modify your source CSS. 3:40
    If you've made lots of important changes in the styles pane, 3:46
    DevTools provides an easy way to let you copy your changes into your source CSS. 3:48
    So after you've made your changes, for example the form element, 3:55
    click the text to the right displaying the file name and line number. 3:59
    And this opens the sources panel displaying the updated form rule, and 4:04
    all your latest changes in style.css. 4:08
    So here I can continue editing the CSS here and 4:10
    simply copy my changes over to my CSS file. 4:13
    Now DevTools does provide a feature that lets you save your source CSS 4:17
    from this sources panel. 4:21
    I've posted a link with instructions on how to set that up in the teacher's 4:23
    notes for this video. 4:26

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