SEO Glossary Part 1: Above the Fold to Anchor Text

This is the first entry in a running SEO glossary, working straight through the alphabet. It covers eight terms from “above the fold” to “anchor text.” Each entry is a standalone definition, not a strategy guide, so use it as a reference rather than a step-by-step tutorial.

Above the Fold

Above the fold is the portion of a webpage a visitor sees without scrolling, a term borrowed from newspaper layout where the front page folded in half on newsstands. In SEO, the phrase matters mainly because of Google’s page layout algorithm, first rolled out in January 2012 and nicknamed the “Top Heavy” update, which targets pages that stack excessive advertising above the visible content area. Google’s own announcement described the change as affecting sites where users “have to scroll down before they see any substantial content.” The initial January 2012 rollout was reported to affect less than 1% of English-language queries; a follow-up refresh in October 2012 (“Top Heavy 2”) was reported by Search Engine Land to affect roughly 0.7% of English-language queries specifically.

There is no fixed pixel measurement for “above the fold” that Google publishes or enforces. How much content is visible without scrolling varies by device, browser chrome, screen resolution, and zoom level, so any number quoted as a universal cutoff should be treated as a rough approximation, not a technical standard. What does matter is Largest Contentful Paint, the Core Web Vitals metric that measures how quickly the largest visible element renders, since a slow-loading hero image or ad unit can hurt both perceived quality and the LCP score. Practically, this term today functions less as a design rule and more as a reminder to keep the initial viewport ad-light and content-forward.

AJAX

AJAX (Asynchronous JavaScript and XML) lets a webpage update parts of its content by exchanging data with a server in the background, without a full page reload. It is the technology behind features like infinite scroll, live search suggestions, and dynamic filtering.

Google could not execute JavaScript reliably in the early AJAX era, but by 2015 it had rolled out full rendering of JavaScript-based content as part of standard crawling. That said, rendering still happens as a separate, later step from the initial crawl and index. Google engineers described this as a “second wave of indexing” at Google I/O 2018, where content requiring client-side rendering can take anywhere from minutes to roughly a week to be fully processed after the page is first crawled. For SEO purposes, this means any content or internal links that only appear after AJAX calls run risk delayed indexing if there’s no server-rendered fallback, and navigation that updates content without changing the URL can make individual views impossible to link to or index separately.

Algorithm

A search algorithm is the set of computational processes a search engine uses to retrieve, evaluate, and rank pages from its index in response to a query. Google has never published an exact factor count, and older claims of “200+ ranking factors” trace back to a now-outdated public statement rather than a current, verifiable list, so it’s more accurate to say Google evaluates a large and evolving set of signals covering relevance, authority, user experience, and freshness.

Early search algorithms, including Google’s original PageRank, ran on comparatively fixed, rule-based logic. That began changing with RankBrain, a machine-learning system Google confirmed in October 2015 as part of its core ranking algorithm, followed by BERT, a natural-language-processing model applied to search in October 2019. These additions mean modern ranking increasingly involves models that learn patterns from data rather than executing a fixed checklist, which is part of why algorithm behavior has become harder to reverse-engineer from the outside.

Algorithm Change

An algorithm change is any modification to how a search engine ranks results. Google groups these loosely into three types: updates that adjust the weighting of existing signals, refreshes that rerun an existing model against current data, and new systems that introduce ranking logic not previously in use.

Named core updates roll out gradually, typically over one to two weeks, meaning two sites can see the same update land days apart. Google has repeatedly stated that most ranking volatility a site owner notices actually comes from the cumulative effect of many smaller changes rather than a single named update. The August 2018 “Medic” update is a concrete example: Google never specified which signal adjustments drove it, and site owners in the health and wellness space spent months guessing at the cause of ranking swings. This illustrates why isolating “what changed” is often harder than site owners expect.

Alt Attribute

The alt attribute is HTML markup that provides a text description of an image, primarily for accessibility (screen readers announce it to visually impaired users) and secondarily as a signal search engines use to understand image content, particularly for image search.

Good alt text describes what the image actually shows without starting with redundant phrases like “image of” or “picture of,” since screen readers already announce that it’s an image. Purely decorative images should carry an empty alt attribute (alt="") so screen readers skip them rather than reading meaningless filler. There is no enforced character limit, though shorter, specific descriptions tend to serve both accessibility and search purposes better than long, keyword-stuffed strings, which search engines treat as a spam signal. Because alt text exists first for accessibility and legal compliance (it factors into ADA and WCAG conformance), that purpose should take priority over any SEO consideration when the two are in tension. A product photo alt attribute reading “red leather men’s wallet, size medium” serves both accessibility and search intent better than a generic “wallet.jpg” filename or an alt attribute that just says “product image.”

AMP

Accelerated Mobile Pages (AMP) is an open-source HTML framework Google announced in October 2015, built around a restricted, stripped-down version of HTML and JavaScript intended to make mobile pages load near-instantly from cache. For several years, AMP was effectively required for a publisher’s articles to appear in Google’s mobile Top Stories carousel.

That requirement ended in mid-2021. Google confirmed that with the rollout of the page experience update, any page could qualify for Top Stories regardless of whether it used AMP, and the lightning-bolt AMP icon was dropped from search results around the same time. With Core Web Vitals now serving as the universal speed standard, non-AMP pages can earn the same performance recognition AMP once had exclusively, which is why the format has become optional rather than advantageous. Sites still running AMP alongside a standard version should weigh the ongoing maintenance cost of keeping two page versions in sync against a benefit that no longer carries the ranking or carousel-eligibility weight it once did.

Analytics

Analytics is the practice of collecting, measuring, and interpreting data about how visitors use a website, in order to understand past performance and inform decisions. In an SEO context this typically means tracking acquisition (where traffic originates), engagement (how visitors interact with pages), conversions (whether visitors complete desired actions), and audience characteristics (device, location, demographics).

Collecting data is not the same as acting on it; a dashboard full of pageview counts with no connection to a business objective produces the appearance of insight without the substance of it. The most useful distinction here is between metrics that are genuinely informative, meaning they connect to a goal and suggest a specific action, and vanity metrics that look good in a report but don’t change any decision. Implementation also carries compliance obligations: GDPR in the EU and CCPA in California both govern how visitor data can be collected and require consent mechanisms for non-essential tracking.

Anchor Text

Anchor text is the clickable text of a hyperlink. It gives both users and search engines context about what the linked page is about, and it’s one of the signals search engines use to interpret the topic and relevance of the destination page.

Before Google’s Penguin update launched in April 2012, it was common practice to build backlinks using exact-match keyword anchor text at scale, since anchor text was one of the more directly manipulable ranking signals of that era. Penguin specifically targeted manipulative link schemes, including unnaturally keyword-heavy anchor text profiles, and made that tactic a liability rather than an advantage. A natural link profile today shows variety: branded terms, partial matches, generic phrases like “read more,” and bare URLs, rather than the same exact keyword repeated across dozens of referring domains. Generic anchors aren’t penalized on their own, and internal link anchor text should generally prioritize clarity for the reader over keyword optimization.

Treat this page as a starting vocabulary, not a final technical reference: verify any threshold or version-specific claim against Google’s current documentation before applying it to a live site, since search terminology shifts faster than any static glossary can track.

Quick reference

Term	One-line definition
Above the Fold	Content visible without scrolling; no fixed pixel standard exists
AJAX	Background data exchange that updates a page without a full reload
Algorithm	The evolving set of processes Google uses to rank pages
Algorithm Change	A modification to ranking logic, from minor reweighting to a new system
Alt Attribute	Text description of an image, primarily for accessibility
AMP	A restricted HTML framework, no longer required for Top Stories eligibility
Analytics	Collecting and interpreting visitor data to inform decisions
Anchor Text	The clickable text of a hyperlink

Sources cited: Google Search Central: Page layout algorithm improvement, Search Engine Land: Google Top Heavy update coverage, <a href="https://www.theregister.com/2021/06/28/googleampcorewebvitals/”>The Register: Google drops AMP requirement (2021)