Algorithms & Quality

B

• BERT algorithm (BERT)

  BERT stands for Bidirectional Encoder Representations from Transformers. It is the language model Google rolled out to its search ranking and snippet systems in October 2019. BERT improved Google's understanding of prepositions, conjunctions, and overall query context — especially for conversational queries.

C

• Core update

  A core update is a broad algorithmic refresh Google rolls out roughly three to four times a year, affecting rankings across all queries and verticals. There is no single fix for ranking drops — recovery is rooted in long-term content quality, expertise signals, and overall site trustworthiness.

D

• Doorway pages

  Doorway pages are pages or sites built primarily for search engines, funneling users to a single destination once they land. Classic patterns: city-by-city landing pages with near-identical content, multiple domains targeting close variants of the same query. A long-standing Google spam policy, tightened by the 2015 doorway update.

E

• E-E-A-T (E-E-A-T)

  E-E-A-T stands for Experience, Expertise, Authoritativeness, Trustworthiness. It's the framework Google's Search Quality Raters use to evaluate content, added "Experience" in December 2022. Not a direct ranking score — it informs the quality signals that rankers learn from. Critical for YMYL topics.

H

• Helpful Content System (HCU)

  The Helpful Content System is Google's framework for distinguishing people-first content from search-engine-first content. Originally launched in August 2022 as a separate sitewide classifier, it was folded into the core ranking signals during the March 2024 core update.

• Hummingbird

  Hummingbird is the algorithm overhaul Google announced in September 2013 — the largest rewrite since Caffeine in 2010. It shifted ranking from keyword-by-keyword matching toward parsing the full query for intent and meaning. Hummingbird is the foundation later systems like RankBrain, BERT, and MUM extended.

I

• Information gain

  Information gain is a score described in Google's [US Patent 11620273](https://patents.google.com/patent/US11620273B2/) measuring how much new information a given document adds beyond what the user has already seen in other documents on the same topic. Rewards original substantive contribution; penalizes the third article on a SERP that just restates the first two.

M

• MUM algorithm (MUM)

  MUM stands for Multitask Unified Model, the language model Google announced in May 2021 as the successor to BERT. Google's claim: 1000x more capable than BERT, multimodal (text plus image), and multilingual across 75 languages. MUM powers Things to Know and underpins parts of AI Overviews.

P

• Page experience update

  The page experience update rolled out to mobile in June 2021 and to desktop in February 2022. It bundled Core Web Vitals (LCP, FID/INP, CLS) with HTTPS, no intrusive interstitials, and mobile-friendliness into a unified ranking signal. Now described as part of Google's broader page experience ranking systems rather than a discrete update.

• PageRank

  PageRank is the original Google ranking algorithm, patented by Larry Page and Sergey Brin at Stanford in 1998. It scores pages by the quantity and quality of inbound links. The public Toolbar PageRank score was deprecated in 2016, but Google has confirmed the underlying signal is still operational.

• Panda algorithm

  Panda was the algorithmic update Google launched on February 23, 2011, to target thin, duplicate, and low-quality content — particularly content farms that had dominated SERPs in 2010. Periodic refreshes ran for five years, then Panda was folded into Google's core algorithm in January 2016.

• Parasite SEO

  Parasite SEO is the practice of publishing content on a high-authority host domain to rank queries the publisher's own site couldn't reach. Common hosts: major news sites, LinkedIn articles, Medium, university subdomains. Google targeted the publisher-host variant directly with the site reputation abuse policy in May 2024.

• Penguin algorithm

  Penguin was Google's algorithmic update launched on April 24, 2012, to combat manipulative backlink patterns — link schemes, exact-match anchor abuse, paid links, low-quality directories. Penguin 4.0 (September 2016) made it real-time and granular, devaluing bad links rather than penalizing whole sites.

Q

• Quality Rater Guidelines (QRG)

  The Quality Rater Guidelines is the public document Google publishes for the thousands of human contractors who evaluate search results. It defines E-E-A-T, YMYL, page quality scoring, and "needs met" assessments. Not the algorithm itself — but the training signal that shapes ranking systems.

R

• RankBrain

  RankBrain is Google's first major machine learning system applied to search ranking, confirmed in October 2015. It helps interpret novel, ambiguous, or never-before-seen queries by mapping them to similar known queries. Still operational today as one of many signals in the ranking system.

• Reviews update

  The reviews update — now called the Reviews System and folded into the core ranking system in November 2023 — targets thin or aggregator-style review content. Google rewards first-hand evaluation, side-by-side comparison, original photography or video, and clear evidence the reviewer used the product.

S

• Site reputation abuse

  Site reputation abuse is publishing third-party content on a high-authority host site primarily to manipulate rankings, when that content has little oversight from the host and is unrelated to its main purpose. Codified as a Google spam policy in May 2024. Targets coupon sections, sponsored deal hubs, and rented subdirectories.

• Spam update

  A spam update is a targeted enforcement run against Google's published spam policies — cloaking, sneaky redirects, scaled content abuse, link schemes, doorways. Distinct from a core update, which reweights quality signals broadly. Recovery requires removing the offending pattern, not waiting it out.

Y

• YMYL (YMYL)

  YMYL stands for "Your Money or Your Life" — the class of queries where low-quality content can hurt users' health, finances, safety, legal status, or civic participation. Defined in Google's Search Quality Rater Guidelines. YMYL pages are held to a higher E-E-A-T standard than ordinary content.