SharedCount gathers data directly from Facebook, so our numbers match up with theirs 100%.
You may check Facebook Debugger and verify if Sharedbook's results are correct.
There are various reasons why you would get different results, they are;
This means that there are actually 8 possible distinct URLs for any given website, and this may return different data associated with them. For example:
And this is what we call Canonicalization.
What is a Canonical URL?
Canonicalization is the process of picking the best URL when there are several choices, and it usually refers to home pages.
For example, most people would consider these the same URLs:
But technically all of these URLs are different. A web server could return completely different content for all the URLs above. When Facebook “canonicalizes” a URL, we try to pick the URL that seems like the best representative from that set.
Important things to note:
A small percentage of URLs don't return accurate results with Facebook. That's because Facebook normalizes shares for pages that declare a canonical URL, either with OpenGraph URL or canonical URLs meta tags. That means they'll aggregate the shares across all those URLs that share a canonicalized URL. For URLs where these canonical URLs are set incorrectly or inconsistently, the data you'll get for those URLs and their shares will be limited.