JScript is a script-based programming language from Microsoft which offers (almost) the complete functional scope of an object-oriented programming paradigm. JScript is primarily used as a code component or as a complement of dynamic HTML documents to improve the user experience on websites.

JScript is a private, proprietary development of Microsoft, in order to dispense with using Netscape and the JavaScript license. Although JScript is principally based on JavaScript, it offers more features and can only be interpreted by Internet Explorer.

Other browsers may sometimes require plugins. The dispute between Netscape and Microsoft has been ended with the introduction of a language standard by the W3 Consortium. The result was ECMA script, a standard that allows the implementation of both languages ​​on all browsers. Both JScript and JavaScript can now be considered implementations of ECMA script. A newer version of JScript is JScript.NET, which was supplemented with the .NET platform function from Microsoft.

Features / practical relevance[edit]

Typical applications of JScript are dynamic HTML documents that are generated on the client side, if a website is accessed. JScript runs in the browser and not on the server. If a user, for example, puts an online store product in their cart, it is often implemented with JScript, so that the website does not have to be loaded again from the server. Forms, search boxes, dialog boxes or banners can be programmed with Jscript as well. Downloading of images and text or access to the source code of a website can be prevented.

JScript applies the sandboxed principle. The code is executed in a cage and is independent of the user’s operating system and the server on which the HTML documents are stored. Even if scripts are disabled in the browser, HTML documents are displayed. The reason for this is mainly security. The operating system should not be reachable through script applications. At the same time, the requests to the server are reduced by the sandbox principle, which affects server performance positively.

Script errors should be avoided so that no bugs arise which could have a negative impact on search engine optimization.

Relevance to SEO[edit]

Search engine operators recommend using scripts only sparingly on webpages.[1] Because the crawler cannot interpret the code. In particular, four cases can be distinguished:

  • If a website is only accessible via JScript, it cannot be indexed.
  • If a redirect is executed using a script, the search engine will not forward the Link juice. A redirect (301) without JScript should be chosen, so that the reputation of the website gets passed on.
  • If a text is output via a script, it is not readable by the search engine. It is better to issue the text directly as an HTML document or to use other formats that are supported by the search engines, for example, PDFs.
  • Navigation menus that are programmed with scripts must be avoided. Again, the search engine cannot navigate through the menu to read out the contents of the menu items.


  1. Webmaster Guidelines. Webmaster Tools. Accessed on 11/07/2013