OPen Site Explorer listing criteria?

[G-DC]

Checking link data for a potential client who has given me access to their websmaster tools account, I've noticed that Google list over 150,000 "Links to Your Site" but yet OSE only reports a tiny fraction of this number.
I have manually verified that there are in fact direct links from the sites that are listed in Webmaster Tools but not in OSE.

Does OSE discard some links? Is there a reporting lag? Does anyone know why there would be such a large discrepancy?

[EricaMcGillivray]

OSE's data comes from our own crawlers. The simple fact is that our crawlers do not reach the same amount of data that Google's do. We're working on it and continually improving this. We use our own crawlers because we believe in the quality of getting the data for ourselves.

Hope this helps!

[G-DC]

Thanks Erica but in this case there are 19011.4% more links in GWT than OSE.
Would your diagnosis explain a gap of that magnitude or should I be looking for something else?

[EricaMcGillivray]

That does seem a little odd. I tried finding info on how many links Google claims to have indexed, but couldn't find a reliable source. We indexed 38 billion domains and 387 billion links in our last Linkscape update.

That said, with how our crawlers work, if you're getting backlinks on domains with loads of other links on the page (which often happens if you're buying links), our crawlers will not grab every link on the page and that would definitely lower your backlinks profile with OSE.

[G-DC]

Thanks anyway but no this client has never before done any structured SEO or link building. The site is a long established site with thousands of clients linking back to it and the checks I've done show that they are natural links.
I'll do a bit more digging but my previous observations had been that GWT underestimated the links versus OSE or previously Yahoo Site explorer. This is so far the other way around it is odd.