Mortgage lenders use FICO scores, which range from 300 to 850, drawn from each of the three credit bureaus (Equifax, Experian, TransUnion). They take the middle of your three scores as your qualifying score.
Score requirements vary by loan program: 580 for FHA with 3.5% down, 620 for conventional and USDA, 700+ for best jumbo pricing. The biggest jump in pricing is between 660 and 760 — every 20 points in that range can move your rate noticeably.
Mortgage scoring uses an older FICO model (FICO 2, 4, and 5) that scores you slightly differently than the FICO 8 you see in apps like Credit Karma. Don't be surprised if your mortgage score is 20–40 points different from what you've been watching.