If you're concerned that Google's move to mobile first indexing might negatively affect your site's visibility and search engine ranking...
What is a Friendly URL?
A friendly URL is a web address that is readable to both a human user of the website and a search engine spider. With many large or dynamic websites the URLs are generally formatted in a way that isn’t beneficial to the user or a search engine from an SEO perspective.
For example, this is the type of URL you may see on a dynamic website:
Ideally the URL would provide both context and relevance to the information on that page. So for example, if the web page was for a web company offering web design services, the friendly URL might look like:
Regarding SEO, friendly URLs can also include page specific keywords to help improve the relevance of those pages. If your site is using unfriendly URLs, you can use mod-rewrites to change all your pages. However, if you do you will need to add 301-redirects from your old URLs to your new URLs so that Google knows that the location of the pages have permanently been moved.