What is CLASSID ?

ActiveX controls are reusable software components that are used to add special functions to web sites or desktop applications. Browsers use the ‘CLASSID’ of the ActiveX Control on a web page to determine if the control already exists on the system. If they do not they are automatically downloaded from the website.

Before you go ahead and download a registry cleaner understand why it is necessary. As a web page loads on your system, you may be prompted to install several ActiveX components before the page can be fully downloaded. This is so that the browser can interpret the ActiveX components and display them properly on the system. This only would only occur if the controls used in the web page were not already on the system. If you decline permission for the installation, the page will not function properly.

However, once these ActiveX controls are on your system, you won’t have to download them again, even when you come across them on other web sites. These download clutter up the registry over time and need to be removed with the help of some registry shareware cleaner.

Other ID Tags

So how can the web page determine that the required ActiveX controls are not installed on the system or not? The browser does this by referring to the ‘CLASSID’ in the ‘OBJECT’ tag of the web page. To cut a long explanation short, an ActiveX control is added to a web page using the and container tags. The ‘CLASSID’ is unique to each ActiveX component.