The folks over at credit.com have written quite an extensive article on the impact of getting a mortgage pre-approval on your credit rating. The short answer is, they have an impact, but it’s quite small. For more details, the article is well worth the read, as they go into the difference between hard inquiries and soft inquiries, the impact and what constitutes each, and they go on to provide links to different credit scoring models that lenders use, as well as the standard “how to check my credit”.
Theresa Springer’s Blog
How Does A Mortgage Pre-Approval Impact Your Credit Rating?
September 1, 2015