Setup instructions for Sybu JavaScript Blocker – Google Chrome Extension


Sybu JavaScript Blocker is a Google Chrome Extension to quickly block JavaScript (JS) files from being loaded by the browser.

It has been designed to be easy to use.



Install from Google Chrome Web Store


After you have installed the extension.  Pin the icon to toolbar.

It will be visible to the right of the Chrome search/address bar.


It is a little Blue Shield icon or Blue Sybu icon depending on the application state. Click the icon.

The Sybu JavaScript Blocker has 3 modes:  OFF | My Rules | Block All

Mode:  Off

The extension is disabled and will not block any JavaScript files

Mode: My Rules

In this mode the extension will block or allow JS files based on the rules specified in Block Rules and Allow Rules

User Interface


sd_jsblock_120_06b JavaScript file was allowed and loaded. No rule was applied.

 JavaScript file was allowed and loaded, based on Allow Rule.

sd_jsblock_120_06cJavaScript file was blocked, based on Block Rule

1,2,3.. The numbers next to listed items indicated the processed sequence

sd_blocker_indicator The total number of files blocked.  Click to sort.


Click to edit the Block Rules

Click to edit the Allow Rules

Click to add or remove sites that will always be blocked or always be allowed.

Click to view or add sites that are temporary allowed.

Click to edit the extension options

File is currently allowed.  Click to add Block Rule

File is currently allowed. Click to remove Allow Rule

 File is currently blocked. Click to remove Block Rule

 File is currently blocked.   Click to add Allow Rule

Block Rules

Click the  button, to show the setup

Block Scripts from 3rd party domains.

When enabled (recommended),  the script will block JavaScript files that are not from the same domain as the requested page.  This will immediately block a lot of trackers and advertising links, without the need to specify individually.  In the example below you will notice when this option is enabled any script not from the domain was blocked.

Additional block rules can manually be entered. These can be complete URLs, or any part of, as shown below

Rules can also be added by clicking on the indicator

In this example if you choose:

1: analytics – This will block any JavaScript on any page that contains gpt as part of the URL

2: analytics.js – This will block the JavaScript with filename gpt.js on any page

3:    – This will block JavaScript file originating from 3

4:   – This will block any JavaScript originating from domain

5: Other.  This will block any JavaScript on any page that contains the specified text as part of the URL

Rule Options:

In some cases you may want to apply the block rule to the script, but only is the script originated from a request from a specific website.

To unblock a file (and remove the rule associated with it) click on the [-] button next to the file being blocked.
or simply remove the text from list of items in Block Rules

Allow Rules

Click the  button, to show the setup

NOTE: An Allow Rule will override a Block Rule.

The setup of Allow Rules is similar to Block Rules. Simply add a list of items (full URLs, or partial names).

Good/Bad Domain

Click the button, to show the setup

Click to add or remove domain that will always be blocked or always be allowed.

When it is required that no rules are applied that a website request, the website domain can be added.  This may be useful for specific sites like Gmail for Facebook, to function properly.  The domain for the current web request is already displayed, and you can simply click the Add Good or Add Bad button as seen in the example.  Simple click the button, it will add it, save the setting and reload the page automatically.   Alternately you can also manually add / remove domains in the space provided.

Temporary Rules

Click the temporary button to view rules that are temporary and will expire.

In some cases when you are visiting website you may not want to set a permanent rule. This is useful for sites that are not frequently visited.

  • Specific temporary allow rules can also set for individual scripts
  • Allow rules for temporary allow sites and scripts can be viewed or cleared

Rules expire under following conditions.

  • after specific duration, the default is 1hr, but can be changed in the options of the extension.
  • after specific number of requests, the default is 10, but can be changed in the options of the extension.
  • when the browser is closed

 Mode: Block All

In this mode all JavaScript will be blocked, but you will find that most pages do not render properly.  So options are available to allow some JavaScript to be loaded. Exceptions can be added in Allow Rules.   

So for example it may be useful not to block a script like jquery since this is used on many websites to display content dynamically.

Options Menu:

  • Import Rules (Replace).  An exported file can be imported.  This will replace all existing rules.  The filename must start with SybuJsBlocker
  • Import Rules (Merge). The file being imported will be merged with existing rules.  If the rule does not exist, it will be added.  If the rule already exist, it will be ignored.
  • Export Rules.  All rules can be exported to a file.  The file is automatically saved in the web browser’s Downloads folder.   The filename is automatically generated, starting with SybuJsBlocker-[Bx-Ax-Wx]-<date>.json
  • Options for temporary rules added.

Like it and show some love…

The Extension is free, there is no monetization, no trackers, no advertising.  If you use the extension, please consider liking Sybu Data on Facebook and/or giving it 5* on the Google Chrome Store. – This will be appreciated.

Release Notes

Version history and release notes 


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