How do you verify clean backlink profile nowadays (free method)?

[aidenhera]

There is difference between manual penalty (for the whole domain or partial) that you see in WMT and algorithm penalty which you have no way to check just can guess by the ranking of the website. For example old auctioned domain rank for long tail keywords (eg: the H1 tag of the article) at page 8. Clearly something is wrong there as you are using something like "How to use iPad to check the pressure of your tires" - the first 7 pages are absolutely irrelevant, yet they beat your own article.

could be kw density too

 

[robinmym]

Following this post

 

[AngelSeo]

could be kw density too

Not really as I am talking about PBN - the content can be restored from the archive or from human writer with no specific keywords, just a topic. Anyway if you over optimize your keywords is again algorithm penalty - you have no message in webmaster tools, yet your ranking suffers.

 

[Initial Effort]

OP, the one solution if you were to buy clean domains is you ensure you buy them from someone who has good reviews and expertise.

 

[affk2011]

Use ahrefs to look at the links manually, use way back machine to check what kind of content was on it in the past and most of all, enter the domain in google to see if it's even indexed