I have a list of 300 domains. I want to find out which of them are banned on Google. How can I easily find out which ones would have Google penalties?
Seeing if a domain name is penalized isn't an easy process. Google is tight lipped about penalties; it only shares information about the penalty (or even the fact that there is a penalty) with a verified webmaster for that domain.
The typical way to see if the domain has been penalized it to verify the domain in Google Webmaster Tools and look for messages from Google. You would need to own the domain names and manually review them one at a time for this to work.
There are some third party tools that will give you a great deal of information about domains. While they won't tell you specifically if Google penalizes them, they will give you metrics that can help you decide whether or not Google is likely to penalize them. One such tool is Moz's Open Site Explorer. It won't let you do 300 easily, but you can do five at a time:
There is no mass checking that I can see. Especially against Google.
**WARNING: Google will block asscess for the following reasons: It feels as though you are trying to scrape, reverse engineer SERPs, or submit mass queries by an agent of any kind. This incudes using the Google API. Google will also block IP addresses that appear in some black-lists. Which ones? I have not researched this. However, Google will at least tell you that they blocked your accesses because they found you in an RBL. These are usually related to mass Whois and DNS requests (and maybe others) where a service reported you to a black-list. As well, some human users can find themselves blocked because of suspicious activity. Fortunately, these blocks do not last too long and Google will tell you how long you will be blocked for. So be careful.
Assuming that there is a website for each domain and that the domain name is not parked, the fastest and simplest way is to do a penality check is to search for the domain name only. For example, www.bobcatrescue.com would be a search for bobcatrescue. If the domain appears within the first one or two pages, then you are okay. Depending upon the condition of the domain, it can appear on the third or forth page too, however, if it appears much after that, then it highly likely that the domain is penalized.
I also did a search for Google domain penalty checker: https://www.google.com/?gws_rd=ssl#q=google+domain+penalty+checker which shows several options. There are some free tools and paid tools. I did a little digging for one I used a couple of years ago that I thought was excellent.
There may be others, but I liked this one. It details which penalties hit the site, when, and the effect. It is very detailed and should tell you what you want to know. I am not sure there is a limit on this tool, but you can try it and find out.
If you want details on the specific penalty, you can check: http://moz.com/google-algorithm-change
That should do it. Between these two links, you should be able to analyze any site for specific penalties, when, how much loss there was (gains too), and why.