SEO glossary
Short definitions of the SEO terms you actually use — for quick answers in briefs and stand-ups.
Canonical URL
A canonical URL is the "primary" version of a page you tell search engines about via `<link rel="canonical">` to prevent duplicate-content indexation.
CLS — Cumulative Layout Shift
CLS — how much the layout "jumps" during load. Target: ≤ 0.1.
Core Web Vitals
Core Web Vitals are Google's three user-experience metrics: LCP (loading speed), INP (responsiveness) and CLS (visual stability).
hreflang
hreflang is the attribute multilingual sites use to tell search engines that a page has language alternates.
INP — Interaction to Next Paint
INP — the time from a user interaction (click, tap) to the rendered result. Replaced FID in March 2024. Target: ≤ 200ms.
LCP — Largest Contentful Paint
LCP — the time until the largest visible element finishes rendering. Target: ≤ 2.5 seconds at the 75th percentile.
noindex
noindex is the directive that bars search engines from indexing a page. Set via meta tag or X-Robots-Tag header.
robots.txt
robots.txt is a plain-text file in the site root that tells search bots which sections to crawl or skip.
sitemap.xml
sitemap.xml is an XML file listing all your important URLs that you submit to search engines to speed up and clarify indexing.
Yandex IX (ICS)
IX (Site Quality Index, sometimes ICS) — Yandex's public 0-to-∞ metric reflecting the site's usefulness in Yandex's view.
SEO terminology glossary
The Site Metrics Tool glossary is a dictionary of current SEO terms and concepts with bilingual definitions, usage examples, and cross-links to related entries. The goal is to collect everything you need to know about SEO terminology in one place: from basic abbreviations (SERP, CTR, CPC) to advanced concepts (E-E-A-T, BERT, MUM, crawl budget, hreflang). Each term gets a one-or-two-sentence definition, an extended explanation with context, and links to our tools and blog posts where it shows up in practice.
- Every term: definition + extended explanation + examples
- Cross-links between related terms
- Section navigation for browsing by topic
- Full-text search across the whole glossary
How terms are grouped
The glossary splits into six topical blocks for easy navigation. For a specific term — use search. To go deep on one topic — open a section and read top to bottom. Each section holds 15–40 terms, from foundational to more specialized.
Core SEO concepts
"Foundations" is the floor — nothing above it works without these. Here we explain what a SERP is and what kinds (organic, paid, featured snippets, local pack), how engines discover and index content, how on-page differs from off-page, the three named ranking factors (relevance, authority, usability), what behavioral signals are and how Yandex / Google weight them.
- SERP, organic, paid, featured snippet, local pack
- Crawling, indexing, deindex, sandbox
- On-page, off-page, technical SEO
- Relevance, authority, behavioral signals
Metrics and traffic analytics
The measurement track. We cover CTR (what counts as a good CTR for different positions), CPC (how it forms, where to read it), bounce rate (when low is bad vs when it's actually good), conversion rate (micro vs macro goals), session duration, pages per session. Separate posts cover GA4 setup after the death of Universal Analytics, Yandex Metrika workflows (webvisor, heatmaps, segments), and how to reconcile data across the two correctly.
Technical terms
The biggest section. Everything about technical implementation: robots.txt (syntax, directives, User-agent vs Disallow), sitemap.xml (spec, limits, sitemap-index), canonical (purpose, common bugs), hreflang (multilingual sites), schema.org (Organization, Article, Product, BreadcrumbList, FAQPage), SSR vs prerender vs hydration, viewport, mobile-first indexing, crawl budget, lazy loading.
- robots.txt: User-agent, Disallow, Allow, Sitemap, Crawl-delay
- sitemap.xml, sitemap-indexes, the 50 000 URL limit
- Canonical: self-canonical, cross-domain canonical
- Hreflang: x-default, region codes, reciprocal links
- Schema.org: core types and required fields
Core Web Vitals and UX metrics
The speed and UX track. Here are the terms and metrics officially part of Google's Page Experience Signals: LCP (Largest Contentful Paint — the main contentful element), INP (Interaction to Next Paint — responsiveness, replaced FID in 2024), CLS (Cumulative Layout Shift — layout stability). Plus adjacent metrics: TTFB (Time To First Byte), FCP (First Contentful Paint), TBT (Total Blocking Time), Speed Index, and optimization techniques: lazy loading, preload, prefetch, critical CSS, Resource Hints.
- LCP — thresholds, typical causes of slow LCP
- INP — why it replaced FID, how to measure
- CLS — what causes shift, how to avoid
- TTFB, FCP, TBT — supporting metrics
- Lazy loading, preload, critical CSS — optimization techniques
Backlinks and anchors
The link-profile track. Terminology: backlink, internal link, external link, anchor types (exact match, partial match, branded, generic, naked URL), link attributes (rel=nofollow, rel=sponsored, rel=ugc, rel=noopener), authority metrics (Domain Rating by Ahrefs, Domain Authority by Moz, ICX by Yandex), link-building methods (guest post, broken link building, skyscraper, link exchange), disavow files to drop toxic links.
- Backlink, anchor, dofollow vs nofollow
- rel=sponsored, rel=ugc — newer attribute types
- Domain Rating, Domain Authority, ICX
- Disavow file: Google and Yandex formats
- Toxic links: what counts and how to handle
Google and Yandex algorithms and updates
Official algorithms and major updates that shape the SERP. Google side: historical (Panda, Penguin, Hummingbird, RankBrain), modern (BERT for query understanding, MUM for multimodal analysis, Helpful Content System against low-quality content, Spam Updates, Core Updates). Yandex side: ICX (site quality index), Minusinsk (against bought links), Palekh and Korolev (neural query understanding), Y1 (the latest big update).
- BERT, MUM, RankBrain — query understanding
- E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness)
- Helpful Content System — against AI content farms
- Minusinsk, Palekh, Korolev — Yandex algorithms
- Core Updates: how to respond to a traffic drop
How to put the glossary to work
The glossary is useful in a few scenarios. Reading a blog or doc and hitting an unknown term — open the glossary in a side tab as a reference. Drafting a spec for a contractor or developer — copy the definition and related terms so everyone speaks the same language. Onboarding a teammate — send a section link as starter material. Writing your own content — borrow definitions as ready short formulations.
Where the definitions come from
Every definition is written by a Site Metrics Tool expert — usually either an SEO analyst who works with the concept in the platform every day or an engineer who shipped the corresponding feature. Each term carries a link to the primary source: Google Search Central docs, Yandex for Webmasters, W3C specs, MDN. We don't paraphrase other glossaries — every entry is original, with examples from real work. If a definition has an error, drop us a note.
Glossary — frequently asked questions
How many terms are in the glossary right now?
Over 150 in both languages. We add new terms as they appear (new algorithms, new techniques) and update existing ones whenever official thresholds or definitions shift.
Can I download the whole glossary?
No direct PDF / docx export today, but it's planned. If you need it now, drop us a note — we can prepare a Markdown / JSON dump by hand.
Can I quote definitions in my own material?
Yes, with attribution and a link to the glossary page. If you'd like to translate and republish in full on another site, write to us — usually we say yes with attribution preserved.
How is your glossary different from Wikipedia or Moz?
Wikipedia is for everything and usually 2–3 years behind on SEO. Moz is an excellent English resource but lacks a Russian-speaking audience. We focus on two languages with current examples for both Russian and international markets.
Do you accept term suggestions?
Yes, write to support@sitemetricstool.com. If the term is genuinely useful, we add it within a couple of days.
Is the glossary paid?
No, fully free, no signup, no view limits. Part of our open material, alongside the blog.
Do you update old definitions?
Yes, especially after big algorithm updates. After FID was retired and INP joined Core Web Vitals, we rewrote every related entry. Each term page shows its last-updated date.
Is there an API to embed the glossary in my product?
No API today. If you have a concrete case, write to us and we'll consider it.