No, using a "Filter by Category" function on a website is not inherently bad for SEO. In fact, it can actually improve the user experience and help search engines better understand the organization of your content.

However, it is important to ensure that the implementation of the filter function is done correctly. If the URLs for the filtered pages are not properly handled, it can lead to duplicate content issues and negatively impact SEO. It is recommended to use canonical tags or URL parameters to avoid this.

Additionally, if the filter function generates too many pages with thin or low-quality content, it could potentially harm SEO. It's important to ensure that the filtered pages have enough unique and relevant content to provide value to users and search engines...