I start building new theme from scratch and I add custom.css to mytheme->magento_theme->web->css

when i test new css with simple code website not working correctly

I already:

Add css to default.head.blocks.xml

Deploy static content

  • can you please share your coed in questions?
    – Abdul
    Commented Dec 30, 2017 at 13:03
  • You can import your custom css into theme's _extends.less and deploy and check Commented Dec 30, 2017 at 14:01
  • Check with private browser to see changes... Because it doesn't make cache.... Else delete your custom css in pub/static/yourtheme to check your changes Commented Dec 30, 2017 at 14:15
  • working with me by add _extends.less to customer moduel
    – Magento
    Commented Dec 30, 2017 at 15:35

2 Answers 2


You need to add default_head_block.xl file in your custom theme in Magento_Theme directory.

Add your custom css file to app/design/frontend/namespace/theme/web/css/custom.css


and copy this code

<?xml version="1.0"?>
    <page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
            <css src="css/custom.css" />

After adding this, delete your pub/static/frontend/ directory and deploy static files.


The file that you are using needs to be default_head_blocks.xml, not default.head.blocks.xml. This file can live in a lot of places, but i prefer to have it here:


Make sure the css file is should up in the pub/static/frontend folder structure. The css might be in different places inside those fodlers depending on your set up, so i can say the exact path. But it needs to be in there for the browser to see it. This is easy to check as the browser will give you a 404 on the file if the xml is set up correctly.

Double check the syntax of your file. It should look something like this:

<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
        <!-- Google Fonts -->
        <!-- <link src="https://fonts.googleapis.com/css?family=Open+Sans:300,400,600,700,800" src_type="url" rel="stylesheet" /> -->
        <css src="css/styles-m.css" />

And inside that file, you need to make sure that your xml is valid, i can't count how many times i missed a closing tag that made the file invalid. Test it here:


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