Google’s guide lists current and retired ranking systems and what they do, on one centralized page.

Google has published a new guide to its Search ranking systems which have been released over the years.

It covers both those in use currently and those which no longer are, listing them in one document.

It’s a handy resource with which to keep up to date with the systems Google uses to rank search results, and what they all do.

Google is also clarifying its terminology, differentiating between updates and systems to avoid confusion. For example, the new system to measure the helpfulness of content was called the Helpful Content Update, but it is in fact a system constantly operating in the background.

A system is always running, but it can receive updates to improve it.

Going forward, Google will be more precise with its wording when differentiating systems from updates.

“Yes, we’ll still have things like a “helpful content update” or a “product reviews update”, but, when possible, we will explain those as updates to the respective systems, such as the “helpful content system” and the “product reviews system.” We’ll also be refreshing our help pages to reflect this terminology change, over time.“

• BERT
• Crisis information systems
• Deduplication systems
• Exact match domain system
• Freshness systems
• Helpful content systems
• Link analysis systems and PageRank
• Local news systems
• MUM
• Neural matching
• Original content systems
• Removal-based demotion systems
• Page experience system
• Passage ranking system
• Product reviews system
• RankBrain
• Reliable information systems
• Site diversity system
• Spam detection systems

And these are Google’s retired systems, which have either been incorporated into successor systems or made part of core ranking systems:

• Hummingbird
• Mobile-friendly ranking systems
• Page speed system
• Panda system
• Penguin system
• Secure sites system

For more details of each system, go to Google’s Guide to Search ranking systems.