According to magento 2 theme specification about Layout files processing :

The Magento application processes layout files in the following order:

1/ Collects all layout files from modules. The order is determined by the modules order in the module list from app/etc/config.php.

2./ Determines the sequence of inherited themes [, ..., ]

3./ Iterates the sequence of themes from last ancestor to current:

a. Adds all extending theme layout files to the list.

b. Replaces overridden layout files in the list.

4./ Merges all layout files from the list.

How can I debug and view the layout file for every step of this process ?

  • Do you mean where to put break points? Or what would you expect?
    – BuskaMuza
    Jan 19, 2016 at 20:48
  • Hi, Thank you. My main purpose is printing "merges all layout file" to see how magento 2 layout render. I have added my answer as the below. Jan 20, 2016 at 2:30
  • @ thienphucvx, I used your code but I am unable to create .xml at var/log . Do I need to change anything ?
    – learner
    Mar 24, 2016 at 19:17
  • Could you try to debug to make sure that you created that module correctly like "var_dump something on excute method of observer" to check whether it's working or not ? Mar 24, 2016 at 23:40
  • 1
    Have a look to this developer app, it may help you in the debug process: github.com/magespecialist/mage-chrome-toolbar Aug 22, 2016 at 7:43

1 Answer 1


Finally, I can print all loaded xml layout and know how magento 2 layout is working. It also help us to check whether our custom module layout is loaded or not. The idea is :

  • We listen to an event “layout_generate_blocks_after” and get all loaded tree from that point.

  • Save all loaded tree to an xml file.

1/ We create a new directory Sample/Dev. Create Sample/Dev/registration.php to declare with Magento 2 about our module directory.



2/ Create Sample/Dev/etc/module.xml : To let Magento 2 know about setup version of our module

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="module.xsd">
    <module name="Sample_Dev" setup_version="1.0.0" schema_version="1.0.0" release_version="1.0.1">

3/ Create Sample/Dev/etc/frontend/events.xml. In this file, we will listen to event “layout_generate_blocks_after”

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">

    <event name="layout_generate_blocks_after">
        <observer name="thienphucvx_layout_generate_blocks_after" instance="Sample\Dev\Model\Layout" />


4/ Create Sample/Dev/Model/Layout.php with the content as below


namespace Sample\Dev\Model;
use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;
class Layout  implements ObserverInterface
    protected $_logger;
    public function __construct ( \Psr\Log\LoggerInterface $logger
    ) {
        $this->_logger = $logger;

    public function execute(\Magento\Framework\Event\Observer $observer)
        $xml = $observer->getEvent()->getLayout()->getXmlString();
        /*$this->_logger->debug($xml);*//*If you use it, check ouput string xml in var/debug.log*/
        $writer = new \Zend\Log\Writer\Stream(BP . '/var/log/layout_block.xml');
        $logger = new \Zend\Log\Logger();
        return $this;

5/ Set up new module . In your home website directory. enter CMD command line:

– php bin/magento module:enable Sample_Dev

– php bin/magento setup:upgrade

6/ Refresh the page that you want to see xml file (for example: your home page) and check your handle xml file in var/log/layout_block.xml .

  • I just came across this and it is amazing. Would you mind submitting a PR to Magento 2 so everyone can have this feature? Even releasing a module would help tremendously.
    – mbalparda
    Aug 7, 2017 at 17:52
  • Hi Mbalparda, I don't know how to do it. Could you help me to submit it ? Aug 14, 2017 at 2:00
  • Yep pinged you on Twitter.
    – mbalparda
    Aug 14, 2017 at 14:40
  • 1
    where is the issue/pull-request for upvoting ? link ? Nov 7, 2018 at 14:49

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