SEO Glossary
Fast definitions with implementation notes — built for developers and technical SEO.
301 Redirect
HTTP 301 (Moved Permanently) is used for permanent URL changes and canonicalization to prevent duplicates and consolidate signals.
302 Redirect
HTTP 302 (Found) is a temporary redirect used for short-lived changes, A/B tests, and maintenance. Use 301 for permanent moves.
307 Redirect
307 is a temporary redirect that preserves the HTTP method (POST stays POST). It’s a stricter semantic alternative to 302.
308 Redirect
308 is a permanent redirect that preserves the HTTP method (POST stays POST). It’s a stricter semantic alternative to 301.
401 Unauthorized
401 means authentication is required. If key content returns 401, search engines generally can’t crawl or index it.
403 Forbidden
403 means access is denied. If you accidentally block search bots, pages can’t be crawled or indexed.
404 Not Found
404 means the resource doesn’t exist. Proper 404s aren’t penalized, but lots of 404s, bad internal links, and soft 404s waste crawl resources.
410 Gone
410 indicates a permanently removed resource. It’s a stronger signal than 404 and can speed up deindexing after recrawl.
429 Too Many Requests
429 indicates rate limiting. If search bots frequently get 429s, crawling slows down and indexing updates can be delayed.
503 Service Unavailable
503 means the server is temporarily unavailable. It’s OK for short maintenance windows, but long-term 503s hurt crawling and indexing.
AEO
AEO helps AI answer engines (ChatGPT, Perplexity, Claude, Google SGE) understand and cite your content as a direct answer source.
AggregateRating
AggregateRating describes average rating and review count, often used for Product/SoftwareApplication. It must match visible review data.
Alt Text
Alt text describes an image for accessibility and helps search engines understand image content. It’s important for image SEO and semantics.
Anchor Text
Anchor text is the visible link text. Descriptive anchors help search engines understand the destination topic and improve UX.
Article Schema
Article schema marks up article metadata (headline, author, dates). It improves content understanding and can support eligibility and citation.
Backlinks
Backlinks are links from other websites to yours and remain a key authority signal. Quality, relevance, and natural mentions matter most.
Brand Mentions
Brand mentions are references to your brand across the web (linked or unlinked). They can build trust, awareness, and lead to citations.
BreadcrumbList
BreadcrumbList schema describes a page’s hierarchy path. It helps search engines understand site structure and may improve SERP breadcrumbs.
Broken Links
Broken links waste crawl budget and hurt UX. Fix internal links and avoid redirect chains to improve site quality and discovery.
Brotli
Brotli is a modern compression algorithm often better than gzip, reducing HTML/CSS/JS transfer size and improving load speed.
Cache-Control
Cache-Control is an HTTP header that controls caching behavior. Good caching improves speed and lowers TTFB; bad caching serves stale content.
Canonical URL
Canonical URLs prevent duplicate content from parameters and tracking, consolidating ranking signals to the preferred URL.
Canonicalization
Canonicalization consolidates ranking signals from multiple similar URLs to a preferred canonical URL using canonicals, redirects and link consistency.
ccTLD
A ccTLD (e.g. .tw/.jp) is a strong regional signal. It’s powerful for localization but increases operational and authority-building cost.
CDN
A CDN serves content from edge locations to reduce latency and improve caching. It's important for global SEO and Core Web Vitals.
Citation
In AEO, a citation is when an AI/search system references your content as a source. Improve citations with verifiable, structured, citable answers.
CLS
CLS measures layout shifts. Common causes include missing image/ad dimensions, late font swaps, and dynamic content insertion.
Content Audit
A content audit evaluates pages by performance and quality to decide what to update, merge, prune, or improve via internal links and metadata.
Content Brief
A content brief defines intent, questions to answer, structure, internal links, and sources—making content scalable and rankable.
Content Freshness
Content freshness is how up-to-date content is. Some queries (news, tools, specs) are more freshness-sensitive than others.
Content Gap
A content gap is a subtopic or question you don’t cover but users search for. Find gaps via SERP and competitor analysis, then fill them with clusters.
Content Hub
A content hub is a navigable collection of content around a topic, connecting pillar and cluster pages with clear internal linking.
Content Pruning
Content pruning removes or merges low-value pages to improve site quality and crawl efficiency. It often uses 301/410 and internal link cleanup.
Core Web Vitals
Core Web Vitals are Google's three key metrics for measuring user experience: LCP, INP, and CLS. Learn each metric's definition, good thresholds, optimization techniques, and their real impact on SEO rankings.
Crawl Budget
Crawl budget is how much crawling effort search engines allocate to your site. Large sites and sites with many duplicates benefit most from management.
Crawl Depth
Crawl depth is the number of clicks from entry pages (often the homepage). Deeper pages are harder to discover and accumulate authority.
Crawl Stats
Crawl Stats show Googlebot crawl volume, response times and crawl errors. It helps diagnose crawl efficiency and server issues.
Crawl Trap
A crawl trap is an infinite URL space (params, filters, calendars) that wastes crawl budget and slows indexing of important pages.
Crawl-delay
Crawl-delay is a robots.txt directive to control crawler request frequency. Learn which search engines support crawl-delay, how to configure it correctly, and alternatives when Google doesn't support it.
Crawlability
Crawlability is whether crawlers can fetch your pages and resources (robots.txt, auth walls, and status codes can block it).
Crawling
Crawling is the process where search bots discover URLs and fetch content, influenced by internal links, sitemaps, crawl budget and robots rules.
Critical CSS
Critical CSS is the minimal CSS needed for above-the-fold rendering. Inline it to speed up first paint, and load the rest later.
CSR
CSR renders content in the browser. Pure CSR/SPAs require bots to execute JS, which can slow and destabilize indexing.
CTR
CTR (click-through rate) is the share of impressions that become clicks. Improving CTR increases traffic without changing rankings.
Disavow
Disavow tells Google to ignore certain backlinks. Use it cautiously—typically only for clear manipulative link issues.
DNS Prefetch
dns-prefetch resolves DNS early for third-party origins. It's low-cost with modest benefit and works well for a few likely-used origins.
Domain Authority
Domain Authority is a third-party metric (e.g. Moz), not a Google metric. Use it for relative comparisons and competitive analysis.
Duplicate Content
Duplicate content happens when the same content exists on multiple URLs. It dilutes signals, wastes crawl budget, and causes wrong URLs to rank.
E-E-A-T
E-E-A-T (Experience, Expertise, Authoritativeness, Trust) is the core concept in Google's Quality Rater Guidelines. Learn how to demonstrate experience and expertise in content, build author authority, and strengthen trust signals for better SEO.
Embeddings
Embeddings convert text into vectors for semantic search and RAG retrieval. Structured content with definitions and FAQs is easier to retrieve and cite.
Entity SEO
Entity SEO focuses on entities (people, brands, concepts) and relationships, using consistent naming, structured data and citable content to build understanding.
Faceted Navigation
Faceted navigation creates many parameterized URLs and duplicates. Manage it with parameter strategy plus canonical/noindex controls.
FAQPage
FAQPage schema marks visible Q&A on a page. Keep markup consistent with on-page content and avoid fake FAQs.
FCP
FCP measures when the first content is painted. It’s an early speed signal, though not a Core Web Vitals metric.
Featured Snippet
Featured snippets are direct answer boxes in SERPs. Win them with clear intent alignment, answer-first structure, and concise formatting.
FID
FID is a legacy interaction metric replaced by INP. It measures only the first interaction delay, not overall responsiveness.
Googlebot
Googlebot is Google’s crawler that fetches and indexes web content. It follows most robots rules and site constraints.
Gzip
Gzip compresses text assets (HTML/CSS/JS) to reduce transfer size. It's widely supported and a good fallback when Brotli isn't available.
H1 Tag
H1 typically represents the main page heading. Clear semantics and hierarchy matter more than the myth of “only one H1”.
Heading Tags
Heading tags define content hierarchy and improve both readability and search engine understanding. Use H2/H3 to structure subtopics.
Helpful Content
Helpful content is content that truly helps users. Thin, keyword-stuffed, or copycat content is less likely to perform well long-term.
hreflang
hreflang maps language/region equivalents so search engines show the right page version and avoid cross-language cannibalization.
HTTP to HTTPS
HTTPS is a baseline trust signal. Use permanent redirects and update canonicals/internal links to avoid duplicate HTTP/HTTPS versions.
Hydration
Hydration attaches events and state to existing HTML. Done well it preserves fast first paint and interactivity; done poorly it causes mismatches.
Image SEO
Image SEO covers alt text, file names, dimensions, formats, and lazy loading. Done well, it improves UX, indexing, and image search traffic.
Index Coverage
Index Coverage reports indexed vs not indexed URLs with reasons (duplicates, crawl issues, noindex). It’s great for site-wide diagnostics.
Indexability
Indexability is whether a page can appear in search results. It’s often impacted by noindex, canonicals, duplicate/thin content, and quality signals.
Indexing
Indexing is when search engines process content and add it to their index. It’s affected by noindex, canonicals, content quality and duplication.
INP
INP measures interaction latency (user input to visual update). It replaces FID and reflects main-thread JS long tasks.
Internal Linking
Internal links help bots discover pages, understand topical relationships, and distribute authority. Topic clusters are a practical approach.
JavaScript SEO
JavaScript SEO focuses on how bots crawl and render JS. The most reliable fix is per-route HTML via SSR/SSG/prerender plus correct metadata/schema.
JSON-LD
JSON-LD is a structured data format that helps search engines and answer engines understand your content and entities via Schema.org.
Keyword Cannibalization
Multiple pages compete for the same intent, diluting signals and causing unstable rankings. Consolidate content and signals to one target page.
Keyword Clustering
Keyword clustering groups keywords by similar intent and SERP overlap, enabling a pillar + supporting pages strategy with strong internal links.
Keyword Difficulty
Keyword Difficulty (KD) is an SEO metric that measures how hard it is to rank for a keyword. Learn how KD scores are calculated, differences between tools, and how to combine SERP analysis for better keyword decisions.
Keyword Mapping
Keyword mapping assigns target keywords/intent to specific pages to avoid cannibalization and build a clear content architecture.
Keyword Research
Keyword research maps demand to winnable queries: intent, SERP format, competition, and cluster planning with internal links.
knowledge.json
knowledge.json is a machine-readable dataset (schema.org Dataset) for definitions, tools and FAQs to support AI citation and extraction.
Language Targeting
Language targeting uses translated content, URL structure (e.g. /en) and hreflang to show the right language version in search results.
Lazy Loading
Lazy loading defers offscreen assets to improve initial load, but misusing it can hurt LCP or delay content discovery.
LCP
LCP measures when the largest above-the-fold element finishes rendering. Poor LCP hurts UX and Core Web Vitals performance.
Link Building
Link building earns high-quality backlinks. The sustainable approach is creating linkable value, not buying or manipulating links.
Link Equity
Link equity is the authority/relevance value passed through links. Internal linking determines how equity flows to important pages.
Link Spam
Link spam is low-quality, manipulative backlinks (paid links, link farms, exchanges). It can be ignored or devalued and may harm stability.
llms.txt
llms.txt is an emerging LLM-friendly entry file listing site purpose, key URLs, and citation preferences. Not an official standard but useful for AEO.
Log File Analysis
Log analysis shows what bots actually crawl: URLs, status codes, frequency, crawl waste, and error patterns.
Long-tail Keywords
Long tails are specific, intent-rich queries with lower competition. Scale them with pSEO and use internal links to lift head terms.
Meta Description
Meta descriptions mainly influence CTR and snippet quality. They're not always a direct ranking factor, but they affect SERP performance and conversions.
Meta Description Rewrite
Google may ignore your meta description and generate snippets from page content to match query intent. Provide extractable summaries in content.
Meta Robots
Meta robots controls whether a page is indexed (index/noindex) and whether links are followed (follow/nofollow).
noindex
noindex prevents a page from appearing in search results. Use meta robots or the X-Robots-Tag HTTP header.
OG Image
An OG image (og:image) controls social preview images. Use 1200x630 (1.91:1) as a safe default and beware platform caching.
On-page SEO
On-page SEO optimizes a page’s metadata, headings, content structure, internal links, image alt text, and intent match.
Open Graph
Open Graph controls social share previews (og:title/og:description/og:image). It's not a direct ranking factor, but impacts clicks and shares.
Organization Schema
Organization schema describes your brand entity (name, URL, logo, sameAs). It supports entity SEO and trust consistency.
Orphan Page
An orphan page has no internal links pointing to it, making discovery and ranking harder unless it’s found via sitemap or external links.
PageRank
PageRank is a core link analysis concept for estimating authority. Modern ranking is more complex, but links still matter.
Pagination
Pagination is common on listing pages. Prevent duplicates and indexing chaos with clear URLs, linking paths, and consistent canonical/noindex strategy.
Passage Ranking
Search engines can rank based on relevant passages within a page. Clear headings and answer-first sections improve extractability.
Pillar Page
A pillar page is the hub of a topic cluster: it covers the main topic and links to supporting pages to build topical authority.
Preconnect
preconnect establishes early connections (DNS/TLS) to a third-party origin, reducing latency. Use it for only a few critical origins.
Preload
preload tells the browser to fetch critical resources early (fonts, hero images). Overusing it wastes bandwidth—preload only what's truly critical.
Prerendering
Prerendering outputs static HTML for routes at build time, combining SPA interactivity with indexable HTML for SEO.
Product Schema
Product schema describes product info (name, price, availability, ratings). It’s crucial for ecommerce rich results and must match visible content.
Programmatic SEO
Programmatic SEO uses datasets + templates to publish many long-tail pages, connected via topic clusters to build topical authority.
QDF
QDF means some queries need fresh content (news, trending events, releases). In those cases, recency can strongly influence rankings.
RAG
RAG retrieves relevant documents first, then generates answers. For sites, structured and retrievable content increases your chance to be used in RAG systems.
Redirect Chain
A redirect chain occurs when a URL goes through multiple 301/302 redirects before reaching the final destination. Learn how redirect chains impact SEO, site speed, and crawl efficiency, plus how to detect and fix them.
Redirect Loop
A redirect loop is when redirects bounce between URLs, preventing bots and users from reaching content. It breaks crawling and indexing.
Referring Domains
Referring domains are unique domains linking to you. Often more informative than raw backlink counts for authority distribution.
Region Targeting
Region targeting serves different versions for the same language across markets (e.g. en-US vs en-GB) using hreflang region codes and localization.
rel=nofollow
nofollow is a link attribute hint telling search engines not to fully pass link equity. Common for untrusted or paid links.
rel=sponsored
sponsored marks paid/sponsored links (ads, affiliates, partnerships). It helps compliance and reduces risk from paid link policies.
rel=ugc
ugc marks user-generated content links (comments, forums). It can be combined with nofollow to reduce spam risk.
Render-blocking Resources
Render-blocking resources delay first paint (FCP/LCP). Common culprits are synchronous CSS/JS and heavy third-party scripts.
Review Schema
Review schema marks up reviews and ratings. Reviews must be real and visible on the page to avoid policy violations.
Rich Results
Rich results are enhanced SERP features (FAQ, breadcrumbs, product info). They usually require valid structured data that matches visible content.
Robots Directives
Robots directives include robots.txt (crawl control) and noindex directives (index control). Mixing them incorrectly can break indexing.
robots.txt
robots.txt controls crawling; noindex controls indexing. They solve different problems.
sameAs
sameAs links an entity to authoritative external URLs (official profiles, Wikipedia, GitHub) to support disambiguation and entity connections.
Schema Markup
Schema Markup (Schema.org) describes content semantics so search engines understand entities and qualify for rich results.
Search Intent
Search intent is what users actually want (learn, compare, buy). Matching intent often matters more than stuffing keywords.
Search Volume
Search volume estimates how often a keyword is searched (usually monthly). Use it for prioritization, but intent and value matter more.
Semantic Search
Semantic search uses intent, entities and context, not just keyword matching. Content should cover concepts and relationships for stable rankings and citations.
Semantic SEO
Semantic SEO focuses on topics, entities, and relationships—not keyword stuffing. It pairs well with structured data and clear content structure.
SEO
SEO improves organic visibility through technical foundations, relevant content, and authority: indexability, performance, and structured data.
SERP
SERP (Search Engine Results Page) reflects intent. To rank #1, align your content format and structure to what the SERP rewards.
Site Architecture
Site architecture affects crawl depth, internal link equity flow, and topic clustering. It’s a core lever in technical SEO.
Sitemap
A sitemap helps search engines discover URLs. XML sitemaps are common; large sites split using a sitemap index.
Sitemap Index
A Sitemap Index is an XML directory for managing multiple sitemap files. Learn when to use a sitemap index, how to set it up correctly, and sitemap splitting best practices for large websites.
Soft 404
A soft 404 is when missing content returns 200 or is redirected to an irrelevant page. It creates indexing confusion and quality issues.
Speed Index
Speed Index is a lab metric estimating how quickly page content is visually displayed. It reflects progressive rendering speed.
SSG
SSG generates HTML at build time for each route. It’s fast, cheap, and highly indexable — perfect for content-heavy sites.
SSR
SSR returns fully rendered HTML on each request, helping bots and users see content faster and improving indexability and first paint.
Structured Data
Structured data uses schema.org (often via JSON-LD) to describe entities and attributes so machines can understand your content and potentially show rich results.
Subdirectory
Subdirectories (e.g. /en/) often share domain authority and simplify maintenance. Pair with hreflang/x-default for stable targeting.
Subdomain
Subdomains (e.g. en.example.com) are a common i18n approach, but they may behave more like separate sites than subdirectories.
TBT
TBT is a lab metric measuring how long the main thread is blocked by long tasks. It’s useful for diagnosing INP/FID issues.
Thin Content
Thin content lacks depth or unique value. At scale, it can lead to poor indexing and weaker site-wide quality signals.
Title Rewrite
Google may rewrite SERP titles to match query intent. Clear, relevant, consistent titles reduce the chance of rewrites.
Title Tag
The title tag is a primary source for SERP titles. It influences CTR and relevance signals. Keep it unique, intent-led, and readable.
Topic Cluster
A topic cluster uses a pillar page plus supporting cluster pages and internal links to build topical authority and long-tail coverage.
Topical Authority
Topical Authority is a key metric Google uses to evaluate a website's expertise in a specific subject area. Learn how to systematically build topical authority through Topic Clusters and Pillar Page strategies to improve overall SEO rankings and E-E-A-T signals.
Trailing Slash
Trailing slashes can create two URL variants. Standardize with redirects, self-canonicals, and consistent internal links.
TTFB
TTFB measures how fast the first byte arrives. High TTFB hurts perceived speed and often worsens LCP, impacting UX and competitiveness.
TTI
TTI is a lab metric estimating when a page becomes reliably interactive. It’s not a CWV metric but helps diagnose load-time JS blocking.
URL Inspection
URL Inspection shows indexing status, crawl results, canonicals, and lets you request re-indexing for a specific URL.
URL Parameters
URL parameters can create duplication, crawl waste and canonical confusion. Use canonicals, noindex and consistent internal links.
User-Agent
A User-Agent is an HTTP header that identifies the client (browser or bot). robots.txt rules are grouped by user-agent.
UTM Parameters
UTM parameters track marketing attribution but can create multiple URLs for the same page. Use canonicals pointing to the clean URL.
WWW vs non-WWW
www and non-www are different hosts. Pick a preferred host, use permanent redirects, and keep canonicals/sitemaps consistent.
x-default
x-default is the hreflang default/fallback version used when no language/region match is found.
X-Robots-Tag
X-Robots-Tag is an HTTP response header that can apply noindex/nofollow directives to HTML and non-HTML resources (PDFs, images).
XML Sitemap
An XML sitemap lists URLs you want search engines to discover. Prefer canonical and indexable URLs only.