How to quickly tell if a Magento site is version 1.x or 2.x?

View the page source can check the CSS location.

Magento 1 css file is located here:

mainfolder/skin/frontend/spacename/themename/css/css files

Magento 2 css file is located here:

mainfolder/pub/static/frontend/spacename/themename/locale/css/css files

Clues for Magento 1.x:

1. In page source, there should be words like:

   • varien
   • skin/frontend
   • media

2. When trying to hit URL [website_url]/downloader, it should show Magento Connect page (if downloader has not been removed/renamed)

3. When trying to hit URL [website_url]/install.php, it should show error:

   • FAILED ERROR: Magento is already installed

4. Default URL for contact us page is [website_url]/contacts in Magento 1.x

Clues for Magento 2.x:

1. In page source, there should be words like:

   • pub/static/frontend

2. Default URL for contact us page is [website_url]/contact in Magento 2.x

3. When trying to hit URL [website_url]/magento_version, it should show Magento's major version and edition like:

   • Magento/2.x (xxx)

Note: One more way to check Magento version is check website in https://www.magereport.com/ under Outdated Magento version section.

I hope, it would be more clear now.

Also, adding one more way to check if the website is in Magento 1.x or Magento 2.X.

Magento 2: Mage cookies script tag will be as follows:

<script type="text/x-magento-init">
    {
        "*": {
            "mage/cookies": {
                "expires": null,
                "path": "/",
                "domain": ".www.example.com",
                "secure": false,
                "lifetime": "3600"
            }
        }
    }
</script>

Magento 1 : Mage cookies script tag will be as follows:

<script type="text/javascript">
//<![CDATA[
Mage.Cookies.path     = '/';
Mage.Cookies.domain   = '.example.com';
//]]>
</script>