The Page Diagnostics Tool in SharePoint allows you to review the classic publishing pages and pages on classic team sites. It is a significant component when it comes to fine-tuning SharePoint Performance. The diagnostic tab is one main source of information on the page diagnostics tool. The main purpose of it is to list the rules and mark them if any issues are found. They are marked in red if any issues are found on the page. When a rule is marked red because of an issue, it will also provide a more information link and provide details, and to the remedy.