Google's Webmaster Tools Disavow tool was announced October 16, 2012 on the Webmaster Central Blog. The tool has been the talk of the industry for a few weeks with claims that it removes penalties and a host of other myths and half truths. In Google's words the purpose of the tool is:

The primary purpose of this tool is to help clean up if you've hired a bad SEO or made mistakes in your own link-building. If you know of bad link-building done on your behalf (e.g., paid posts or paid links that pass PageRank), we recommend that you contact the sites that link to you and try to get links taken off the public web first.

Why Did Webmasters Want This Tool?

Google was basically responding to webmasters complaints of problems removing links, stolen content and with the addition of the Paid Links section to Webmaster guidelines introducing new toxic elements that could be planted by competitors. Webmasters needed a way to let Google know they are not responsible for the link ...ignore it!

Negative SEO

I heard about negative SEO many years ago by a friend in the industry. We knew there was a key to making it work which basically entailed that the site have a toxic element in its back link profile. Over the years Google has opened the negative SEO Pandoras box with additions and penalties for paid links. This made adding toxic elements to a back link profile as easy as buying a links, pointing them at the competitor's site and letting things simmer until the link is discovered. At that point it doesn't take many "spammy links" and using a little automation and bad link techniques you could then do damage to a sites rankings.

New Back Link Algorithms

Basically with so many new algorithms like the Exact Match Domain dampener and Penguin update targeting spam and the difficulty getting links removed it was apparent that there needed to be an easier way to manage your back link profile and keep it from getting to the penalization point. Basically a way to do preventative maintenance or as I call it future proofing your work.

Reconsideration Requests

The tool is a big part of the reconsideration request because the disavow tool enables you to upload a list of sites you were unable to get the link removed! Google recommends you still need to make an attempt to remove the link. This is just a more orderly way to deal with sites that do not respond or remove the link.

Link Disavow Tool Video by Google's Matt Cutts

Using the Disavow Tool

File Syntax (below is copy and Paste from Google blog post:

The format is straightforward. All you need is a plain text file with one URL per line. An excerpt of a valid file might look like the following:

# Contacted owner of spamdomain1.com on 7/1/2012 to # ask for link removal but got no response domain:spamdomain1.com # Owner of spamdomain2.com removed most links, but missed these http://www.spamdomain2.com/contentA.html http://www.spamdomain2.com/contentB.html http://www.spamdomain2.com/contentC.html

In this example, lines that begin with a pound sign (#) are considered comments and Google ignores them. The “domain:” keyword indicates that you’d like to disavow links from all pages on a particular site (in this case, “spamdomain1.com”). You can also request to disavow links on specific pages (in this case, three individual pages on spamdomain2.com). We currently support one disavowal file per site and the file is shared among site owners in Webmaster Tools. If you want to update the file, you’ll need to download the existing file, modify it, and upload the new one. The file size limit is 2MB.

Important to add that sub-domains are a separate domain to Google so it would look like this:

# Contacted owner of support.spamdomain1.com on 7/1/2012 to # ask for link removal but got no response domain:support.spamdomain1.com