What’s PageRank?
PageRank is Google’s original algorithm (1998) for scoring how important a web page is. Imagine a "random surfer" who starts anywhere and keeps clicking links:
Chance to jump (1 – d) – the surfer sometimes stops following links and lands on a random page.
Chance to follow links (d) – the rest of the time, the surfer picks one outbound link from the current page.
The PageRank of a page is the probability that the surfer is on that page after many clicks. Mathematically: PR(A) = (1 – d) + d × Σ(PR(T) / C(T))
PR(T) – rank of a linking page T
C(T) – number of outbound links on T
d – damping factor (Google ≈ 0.85; we use 0.5)
Key ideas
More quality links → higher PR
A link from a high-PR page counts more than one from a low-PR page.
Links marked nofollow/ugc/sponsored contribute 0, 301 redirects forward the full PR.
Domain Rank
Domain Rank sums the PRs of all pages on a domain and compresses them using a log scale, making big jumps harder to notice at higher levels.
Why Ahrefs DR differs: Ahrefs crawls a separate index and tweaks the formula, so numbers aren’t identical, but trends (up or down) usually align with our Domain Rank.