Remove GuideService
GuideService is an intrusive Mac application, which you do not want to have to deal with. Its installation is often completed through fake downloads and misleading ads, which promise a great tool. In reality, GuideService has nothing valuable to offer. Its sole purpose is to operate in the background, without revealing its presence. The operations that GuideService executes aim to modify the settings of Web browsers like Safari.
The changes that GuideService introduces concern the default new tab page and search engine that the browser uses. They will be replaced by a 3rd-party site that usually hosts a search service.
Using the Web page that GuideService promotes is unlikely to be a good experience. The search feature will not work reliably, and it may often end up displaying countless ads and sponsored search results. Of course, you are not interested in seeing these when all you want is to browse and search the Web. Furthermore, the results that GuideService shows are often unreliable. We consider GuideService to be a Potentially Unwanted Program (PUP) that has the ability to introduce undesired changes. We advise you to remove it from your Mac by running a reputable security tool for macOS.