$ cat Link Juice Simulator

Every link scheme in this archive is an attempt to move PageRank. This sandbox shows the movement: pages are nodes, links are pipes, and link equity flows between them as particles. Build a network, watch where the juice pools, then run a footprint sweep and see what survives.

How to read the simulation

Each node is a page or site. The number under it is its share of the graph's PageRank, scaled so the whole graph starts with 100 units. A node passes a fraction of its rank through every outbound link, split evenly between those links, and the damping factor (0.85) means 15% of the flow resets to random entry points on each cycle. Bigger, brighter nodes hold more rank. Particle density on a link is proportional to how much juice that link carries.

Hover or tap a node to see its links, how much it passes per link, and its footprint profile. Dashed grey links are nofollow: their particles drift off and evaporate. Dashed red links have been devalued by the sweep and carry nothing.

What each scenario teaches

• Natural web. Link value depends on the linking page's rank divided by its outbound links. One link from a strong page outweighs several weak ones. See Search Manipulation.
• PBN. Expired domains keep equity from their old backlinks, and a network funnels it into one site. The sweep flags the four domains sharing hosting, registrar, theme or tracking IDs; the domain with a distinct footprint survives. See Private Blog Networks and Expired Domain Abuse.
• Link wheel. A ring of Web 2.0 properties mostly recirculates baseline rank, and the perfect ring is itself a pattern.
• Nofollow sculpting. Press M to compare the pre-2009 model, where nofollowed links were ignored, with the current one, where they still count in the divisor and their share evaporates.
• Link farm. Dense reciprocal linking inflates rank inside the cluster, and that density is the footprint.
• Parasite page. A rented page on a strong host borrows the host's internal link equity. The sweep applies the site reputation abuse policy. See Parasite SEO.
• Sandbox. Build your own graph. Nodes added as PBN, Web 2.0 or link farm carry typical footprints.

Model limits

This is a teaching model, not a ranking predictor. It uses the original PageRank formulation (Brin and Page, 1998) with a damping factor of 0.85, solved by power iteration. "Authority" and "legacy backlinks" nodes carry extra seed weight to stand in for backlink profiles outside the sandbox. The sweep is a simple footprint threshold, not a description of how SpamBrain works internally.

Google's systems are far more selective than this model. Nofollow became a hint rather than a directive in 2019 and 2020, and since the December 2022 link spam update Google has described using SpamBrain to neutralize unnatural links rather than count them. Use the numbers to build intuition about how equity moves; they say nothing about how any real site will rank. For how link schemes are actually detected, see Detection & Defense.