Ad injector may refer to any of the following:
1. Software that a website owner can use to embed advertisements into his or her website content automatically is referred to as an ad injector. For example, a website using a CMS, such as WordPress, may use a plugin to add advertisements to its web pages. The ads are often provided by services such as Google AdSense; the number and type of advertisements can be automatically tailored to match the length and content on the web page.
2. The term ad injector may also refer to adware or malware that inserts advertisements into a web page that are not intended to be there. The ad injector software resides on the user's computer and inserts the advertisements into the user's web pages as they are being rendered in the web browser. In some cases, the malicious software may even identify advertisements that are already on a page, and replace them or cover them up with its own advertisements.