My CSS Is Not Getting Injected Through My Content Script

My CSS is not getting injected through my content script

The style sheet is actually injected, but not applied, because other styles override the rules. To get the rules to work, you have some options:

1. Increase the specificity of your CSS rules.

2. Suffix every rule with !important:

   #test {
       margin: 0 10px !important;
       background: #fff !important;
       padding: 3px !important;
       color: #000 !important;
   }
   

3. Inject the CSS via a content script:

   myScript.js:

   var style = document.createElement('link');
   style.rel = 'stylesheet';
   style.type = 'text/css';
   style.href = chrome.extension.getURL('myStyles.css');
   (document.head||document.documentElement).appendChild(style);
   

   manifest.json

   {
     "name": "Extension",
     "version": "0",
     "description": "",
     "manifest_version": 2,
     "permissions": ["tabs", "http://*/*", "https://*/*", "file:///*/*"],
     "content_scripts": [
       {
           "matches": [ "http://*/*", "https://*/*", "file:///*/*"],
           "js": ["myScript.js"],
           "all_frames": true
       }
     ],
     "web_accessible_resources": ["myStyles.css"]
   }
   

   The last key, web_accessible_resources is necessary when manifest version 2 is active, so that the CSS file can be read from a non-extension page.

How to inject CSS using content script file in Chrome extension?

You could add to the manifest's permissions field; See web_accessible_resources. So you would add this to the manifest:

    , "web_accessible_resources": [
        "fix.css"
    ]

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See also "Programmatic injection". and insertCSS().

For most applications, forget all that createElement code and just add the CSS file to the manifest:

"content_scripts": [
   {
      "matches":    ["http://www.google.com/*"],
      "css":        ["fix.css"],
      "js":         ["script.js"]
   }
],

although I understand that you don't want to do that in this exact instance.

Chrome extension content script is not injecting in to most pages

Your content script is probably loading only on pages where the pathname is just /. Add an extra * at the end of your url patterns:

"matches": ["http://*/*", "https://*/*"]

Background.js Doesn't Find Content Injected with Content Script

Wrong document in

var divHTML = document.getElementById('infoDiv').innerHTML;

Please read the Architecture Overview first. Your background script is executed in a separate HTML document, and as such won't "see" the page in the tab.

You'll need to pass the value to the content script to do something with a visible page. You'll probably need Messaging.

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