On a daily basis, I'm reading articles and I receive emails from friends, clients and prospects introducing me to a myriad of web services. Here are three things I check when I'm told about a website.
1° How many individual pages are indexed on Google?
Very easy to do. Just type site:domain.com in Google search bar (replace domain.com by the site to analyse) and you'll get a list of all the indexed URLs. It gives you an idea of how much content has been added to the site. Marketplaces and news services will usually return huge numbers (I've just checked site:ebay.com = 267,000,000 results!).
It's a nice way to compare two competitors.
site:indeed.co.uk = 12,100,000 results
site:cv-library.co.uk = 5,560,000 results
2° What's the traffic's estimate according to Similarweb?
(simply replace the end of the URL by the domain you're researching)
https://www.similarweb.com/website/indeed.co.uk = 34M visits in Feb 2017
https://www.similarweb.com/website/cv-library.co.uk = 7.6M visits in Feb 2017
3° For how many keywords does it rank in Google's top 100 results according to ahrefs?
Indeed.co.uk = 2.9M keywords: https://ahrefs.com/site-explorer/overview/v2/subdomains/fresh?target=indeed.co.uk
CV-library.co.uk = 236,000 keywords: https://ahrefs.com/site-explorer/overview/v2/subdomains/fresh?target=cv-library.co.uk