Technical SEO Glossary — 113 terms defined

301 redirect A 301 redirect is a permanent HTTP status code that sends users and search engines from an old URL to a new one. Google follows it and treats the target as the canonical URL, consolidating ranking signals like PageRank onto the new address and showing it in results.
302 redirect A 302 redirect is an HTTP "Found" status code that tells browsers and search engines a URL has moved temporarily. Users land on the new page, but Google keeps the original URL as the canonical one, so ranking value stays tied to the original instead of consolidating on the destination, unlike a permanent 301 redirect.
307 redirect A 307 redirect is an HTTP/1.1 temporary redirect that sends the client to the URL in the Location header while preserving the original request method and body, so a POST stays a POST. Google follows it but does not treat the target as canonical.
308 redirect A 308 (Permanent Redirect) is an HTTP status code telling clients a URL has moved permanently to the address in the Location header, while preserving the original request method and body (a POST stays a POST). Google treats a 308 the same as a 301 for search.
404 error A 404 error is the HTTP status code a server returns when it cannot find the requested URL. It tells browsers and crawlers that no page exists at that address, without indicating whether the absence is temporary or permanent.
410 Gone 410 Gone is an HTTP status code that tells browsers and search engines a page has been permanently removed and will not return. Unlike a 404 (not found), which leaves permanence ambiguous, a 410 signals the deletion is deliberate and final.
503 error A 503 error (HTTP 503 Service Unavailable) is a server status code telling the client the server cannot handle the request right now, usually because it is overloaded or down for maintenance. It signals a temporary condition, so crawlers should retry rather than treat the page as gone.
5xx errors A 5xx error is an HTTP status code in the 500-599 range that means the server failed to fulfill an otherwise valid request. Common ones are 500 (Internal Server Error), 502 (Bad Gateway), 503 (Service Unavailable), and 504 (Gateway Timeout). The fault is on the server, not the request.
AMP AMP (Accelerated Mobile Pages) is an open-source HTML framework, launched by Google in 2015, for building fast-loading mobile pages using restricted HTML, a managed JavaScript library, and Google-served caches. Since Google's 2021 Page Experience update, AMP carries no ranking or Top Stories advantage.
Article schema Article schema is structured data (using the schema.org Article, NewsArticle, or BlogPosting type) that tells Google a page is a news, blog, or sports article. It helps Search show better headline text, images, and publish dates, and gives AI systems a cleaner author and freshness signal.
Bingbot Bingbot is Microsoft's web crawler, introduced in 2010, that fetches and indexes web pages for Bing search. The same crawl also feeds Microsoft Copilot and Bing-powered AI answers, so a page Bingbot cannot reach stays invisible across both Bing and its AI surfaces.
breadcrumb schema Breadcrumb schema (BreadcrumbList structured data) is JSON-LD markup that describes a page's place in your site hierarchy as an ordered list of ListItems, each carrying a name, URL, and position. Google reads it to show that breadcrumb trail in place of the raw URL in a search result.
breadcrumbs Breadcrumbs are a row of navigational links (like Home > Category > Product) that show a page's position in a site's hierarchy. Marked up with BreadcrumbList structured data, they tell Google how your content is organized and can appear as a category path in desktop search results.
Brotli compression Brotli is a lossless compression algorithm developed by Google that shrinks text-based web files (HTML, CSS, JavaScript) before they travel from server to browser. It usually produces smaller files than gzip, so pages transfer faster. Servers signal it with the Content-Encoding: br header.
canonical tag A canonical tag, written as a rel=canonical link element in a page's HTML head, tells search engines which URL is the preferred version among duplicate or near-duplicate pages. Google treats it as a strong signal (not a strict rule) and uses it to consolidate ranking signals onto that one URL.
canonicalization Canonicalization is the process of selecting one representative (canonical) URL to stand for a set of duplicate or near-duplicate pages, so a search engine indexes and ranks a single version instead of splitting signals across all of them.
CDN A content delivery network (CDN) is a geographically distributed group of servers that cache and serve a website's assets (HTML, CSS, JavaScript, images, video) from an edge location close to each visitor, cutting network latency and speeding up page loads.
client-side rendering Client-side rendering (CSR) is a technique where the server sends a near-empty HTML shell plus JavaScript, and the browser builds the visible page content in the DOM after load. Google can index CSR pages, but only after a separate, deferred rendering phase that runs the JavaScript in headless Chromium.
cloaking Cloaking is the practice of showing search engines different content than the human visitors see, in order to manipulate rankings. Google treats it as a spam-policy violation that can trigger a "cloaking and/or sneaky redirects" manual action.
Core Web Vitals Core Web Vitals are three Google metrics that measure real-user page experience: Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability. They are part of Google's page experience ranking signals.
crawl budget Crawl budget is the number of URLs Googlebot will crawl on your site in a given period. It is set by how much crawling your server can handle (the crawl capacity limit) and how much Google wants to crawl your pages (crawl demand).
crawl demand Crawl demand is how much Google wants to crawl a site or its URLs, driven by their popularity, how stale Google's stored copy has become, and the perceived inventory of URLs it knows about. Together with crawl capacity limit, it makes up a site's crawl budget.
crawl depth Crawl depth (also called click depth) is the number of link clicks it takes to reach a page from the homepage, counting the homepage as depth 0. Pages closer to the homepage are easier for Google to discover, crawl on a tighter cycle, and treat as important.
crawl error A crawl error is a failure a search engine crawler such as Googlebot hits when trying to fetch a URL. It can be site-wide (DNS, server connectivity, or robots.txt failures) or page-level (404, 5xx, or a soft 404), and repeated errors slow crawling and can drop pages from the index.
crawl rate Crawl rate is how fast a search bot like Googlebot requests pages from your site, expressed as the number of parallel connections it opens and the delay between fetches. Google sets it automatically from your server's health, crawling as much as it can without overloading you.
crawl stats report The Crawl Stats report is a Google Search Console report that shows how Googlebot crawled your site over the past 90 days: total crawl requests, total download size, average server response time, host availability status, and breakdowns by response code, file type, crawl purpose, and Googlebot type.
crawl-delay Crawl-delay is a non-standard robots.txt directive that asks a crawler to wait a set number of seconds between requests to your server, throttling how fast it fetches pages. Google and Yandex ignore it; Bing still honors it.
crawlability Crawlability is how easily search engine crawlers like Googlebot can reach, fetch, and move through a site's pages by following links. If crawlers cannot access a page or read its content, that page cannot be indexed, ranked, or cited by AI answers.
crawled - currently not indexed Crawled - currently not indexed is a Google Search Console status meaning Googlebot fetched and evaluated a page but chose not to add it to the index, so it cannot rank. Google says no resubmission is needed; the page may be indexed later or stay out.
crawling Crawling is how search engines discover web pages. Automated programs called crawlers, such as Googlebot, fetch URLs, download their content, and follow the links on each page to reach more pages. It is the first step in search, and a page must be crawled before it can be indexed or ranked.
critical rendering path The critical rendering path is the sequence of steps a browser runs to turn HTML, CSS, and JavaScript into pixels on screen: build the DOM and CSSOM, combine them into a render tree, compute layout, then paint. Shortening it makes visible content appear sooner.
CrUX CrUX (Chrome User Experience Report) is Google's public dataset of real-user, field performance data collected from opted-in Chrome browsers. It powers the Core Web Vitals scores Google uses as a page experience ranking signal, reported as a 28-day rolling average at the 75th percentile.
Cumulative Layout Shift Cumulative Layout Shift (CLS) is a Core Web Vitals metric that measures how much a page's visible content moves unexpectedly while it loads. It scores the largest burst of layout shifts over the page's lifetime, and a good score is 0.1 or less at the 75th percentile of real users.
deindexing Deindexing is the removal of a page or an entire site from a search engine's index, so it no longer appears in search results. It can be deliberate (adding a noindex rule, serving a 404/410, or using the Removals tool) or involuntary (Google dropping pages for quality, technical, or spam reasons).
disallow Disallow is a robots.txt directive that tells search engine crawlers not to fetch URLs matching a given path, for example Disallow: /admin/. It controls crawling only, not indexing, so a disallowed URL can still appear in Google's results if other pages link to it.
discovered - currently not indexed "Discovered - currently not indexed" is a Google Search Console page status meaning Google knows a URL exists (from a sitemap or internal link) but has not crawled it yet, often because fetching it then would have overloaded the server, so Google rescheduled the crawl.
DOM The DOM (Document Object Model) is the browser's in-memory, tree-shaped representation of a web page, built by parsing the HTML and then applying JavaScript. It is the rendered version search engines actually index, not the raw HTML you see in View Source.
duplicate content Duplicate content is the same or nearly identical content available at more than one URL, on a single site or across sites. Google treats most duplication as normal, not a penalty, and simply chooses one canonical URL to index and rank, though it may not choose the one you intended.
dynamic rendering Dynamic rendering serves prerendered static HTML to search engine crawlers while sending users the normal JavaScript version of the same page. Google now calls it a legacy workaround, not a long-term solution, and recommends server-side or static rendering instead.
faceted navigation Faceted navigation is the set of filters and sort options (color, size, price, brand) that let visitors refine a product or listing page. Because each filter combination usually generates its own URL, it can spawn thousands of near-duplicate pages that waste crawl budget.
FAQ schema FAQ schema (FAQPage structured data) is JSON-LD markup that labels a page's question-and-answer content so search engines can identify each question and its answer. Since May 7, 2026, Google no longer shows FAQ rich results in Search, so the markup no longer expands your listing.
First Contentful Paint First Contentful Paint (FCP) measures the time from when a user navigates to a page until the browser renders the first piece of content (text, an image, a non-white canvas, or an SVG). Google rates 1.8 seconds or less as good, measured at the 75th percentile of page loads.
First Input Delay First Input Delay (FID) was a Core Web Vitals metric that measured the time from a user's first interaction with a page (a tap, click, or key press) to when the browser could begin processing that event. Google retired it on March 12, 2024 and replaced it with Interaction to Next Paint (INP).
Googlebot Googlebot is the crawler Google Search uses to discover and fetch pages from the web. It comes in two variants, Googlebot Smartphone and Googlebot Desktop, and since mobile-first indexing most sites are crawled primarily by the smartphone crawler.
hreflang Hreflang is an HTML annotation (rel="alternate" hreflang) that tells search engines which language or regional version of a page to serve a given user. It signals variants like en-US, en-GB, or de-CH so Google shows the right localized page instead of the wrong one.
HSTS HSTS (HTTP Strict Transport Security) is a response header, Strict-Transport-Security, that tells browsers to load a site over HTTPS only and to automatically upgrade any http:// request to https://, so no insecure connection is attempted after the first visit.
HTML sitemap An HTML sitemap is a normal web page that lists links to a site's pages in an organized, human-readable layout. Unlike an XML sitemap (built for crawlers), it is built for visitors, giving them one place to navigate and giving crawlers an extra path to a site's internal links.
HTTP status codes HTTP status codes are three-digit responses a server returns for every request, grouped into five classes: 1xx informational, 2xx success, 3xx redirection, 4xx client error, and 5xx server error. They tell browsers and search crawlers whether a URL loaded, moved, or failed.
HTTPS HTTPS (HyperText Transfer Protocol Secure) is HTTP encrypted with TLS, so data between a browser and a site stays private, tamper-proof, and provably sent to the real server. Google has used HTTPS as a lightweight ranking signal since 2014, and browsers now flag plain HTTP pages as "Not secure."
hydration Hydration is the process where client-side JavaScript attaches event handlers and application state to server-rendered (or static) HTML, turning inert markup into a working app. Until hydration finishes, the page can look loaded but not respond to clicks.
image sitemap An image sitemap is an XML sitemap that lists image URLs so Google can find and index images it might otherwise miss (for example, images loaded by JavaScript). It uses Google's sitemap-image namespace with <image:image> and <image:loc> tags, up to 1,000 images per page.
index bloat Index bloat is when search engines index too many low-value URLs on your site (thin, duplicate, or auto-generated pages) relative to the pages you actually want ranking. It is a quality problem, not a raw page-count problem, and it wastes crawl budget while diluting your site's quality signals.
index coverage report The index coverage report (now called the Page indexing report in Google Search Console) shows which of your URLs Google has indexed, which it has not, and the specific reason for each. It is the main tool for diagnosing why pages fail to appear in search.
indexability Indexability is whether a page is eligible to be added to a search engine's index and shown in results. A page can be crawlable yet non-indexable when a noindex rule, a canonical pointing elsewhere, or thin content stops Google from storing it.
indexing Indexing is the stage after crawling where Google analyzes a page's content, tags, images, and canonical version, then stores that information in the Google index, the database it pulls from to build results. A page that is not indexed cannot rank or appear in AI Overviews.
IndexNow IndexNow is an open protocol that lets a website instantly notify participating search engines (Microsoft Bing, Yandex, Naver, Seznam.cz) when a URL is added, updated, or deleted, so they can recrawl it without waiting for a scheduled crawl. Google tested but does not support it.
infinite scroll Infinite scroll is a UX pattern that automatically loads more content as the user scrolls, replacing numbered pagination. It is an SEO risk because Googlebot does not scroll or click, so content that appears only on scroll can go uncrawled unless it is backed by real, linked paginated URLs.
Interaction to Next Paint Interaction to Next Paint (INP) is a Core Web Vital that measures how quickly a page responds to user interactions, reporting the latency (in milliseconds) of roughly its slowest click, tap, or keyboard interaction across a visit. Google rates 200 ms or below as good and above 500 ms as poor.
JavaScript SEO JavaScript SEO is the practice of making JavaScript-dependent content crawlable, renderable, and indexable, so single-page apps and JS frameworks still surface in search. It addresses how Googlebot crawls, renders (via headless Chromium), and indexes pages whose content is built by client-side JavaScript.
JSON-LD JSON-LD (JavaScript Object Notation for Linked Data) is a JSON-based format for embedding structured data in a web page. It is Google's recommended way to add Schema.org markup so search engines can understand the page's content and generate rich results.
Largest Contentful Paint Largest Contentful Paint (LCP) is a Core Web Vitals metric that measures how long it takes for the largest image, text block, or video in the viewport to render, timed from when the user first navigates to the page. Google treats 2.5 seconds or less, at the 75th percentile, as a good score.
lazy loading Lazy loading defers loading offscreen resources, typically images and iframes, until a user scrolls near them, which cuts initial page weight and speeds load time. The modern method is the native HTML loading="lazy" attribute, which needs no JavaScript.
Lighthouse Lighthouse is Google's free, open-source tool that runs an automated audit of a single web page and grades it 0 to 100 in four categories: Performance, Accessibility, Best Practices, and SEO. It reports lab data (one controlled test load) plus a list of specific fixes, and runs in Chrome DevTools, PageSpeed Insights, or a command-line tool.
log file analysis Log file analysis is the practice of reading a website's raw server access logs to see exactly which URLs search engine crawlers like Googlebot requested, when, and what response code each request returned. Unlike crawl simulators, logs show real bot behavior, not a guess.
meta refresh A meta refresh is a client-side redirect fired by an HTML <meta http-equiv="refresh"> tag that moves the browser to another URL after a set number of seconds. Google reads an instant (0-second) meta refresh as a permanent redirect and a delayed one as temporary, but recommends server-side 301s instead.
microdata Microdata is an HTML specification that embeds structured data inline in the page body, using attributes like itemscope, itemtype, and itemprop to annotate the same content a visitor sees. It is one of three formats Google supports for structured data, alongside JSON-LD and RDFa.
mixed content Mixed content is when a page's HTML loads over secure HTTPS but pulls subresources (images, scripts, CSS, fonts) over insecure HTTP. Browsers auto-upgrade some types (images, audio, video) to HTTPS and block the rest (scripts, stylesheets, iframes) by default.
mobile-first indexing Mobile-first indexing is Google's practice of crawling, indexing, and ranking pages using the mobile version of each page, fetched by the smartphone Googlebot, instead of the desktop version. Google completed the switch for the whole web in 2023, so your mobile page is the one that counts.
nofollow Nofollow is a link attribute (rel="nofollow") that tells Google you would rather not pass ranking credit to, or be associated with, the linked page. Since 2020 Google treats it as a hint rather than a strict rule, so it no longer reliably blocks crawling or indexing.
noindex Noindex is a directive that tells search engines to keep a page out of their index, so it never appears in search results. You set it either with a <meta name="robots" content="noindex"> tag in the page head or with an X-Robots-Tag: noindex HTTP response header.
nosnippet nosnippet is a robots directive that tells Google to show no text snippet or video preview for a page in search results, including AI Overviews and AI Mode. You apply it as a robots meta tag or an X-Robots-Tag HTTP header.
Organization schema Organization schema is structured data (usually JSON-LD, using schema.org's Organization type) that describes a company or brand as an entity, giving search engines its name, logo, URL, social profiles, and contact details so Google can identify the brand and pick its logo and knowledge panel.
orphan pages An orphan page is a live URL on your site that no other internal page links to, so it sits outside your navigation and link graph. Because crawlers find pages mainly by following links, orphans are hard to discover, get little internal PageRank, and often stay unindexed or rank poorly.
page experience Page experience is a set of Google signals measuring how users perceive interacting with a web page. It bundles Core Web Vitals with mobile-friendliness, HTTPS, and the absence of intrusive interstitials, and Google treats it as a group of concepts its ranking systems reward, not one single ranking factor.
page speed Page speed is how quickly a web page loads its content and becomes usable for a visitor. Google measures it two ways: lab data from simulated tests (Lighthouse) and field data from real Chrome users (CrUX), summarized by the Core Web Vitals for loading, responsiveness, and visual stability.
pagination Pagination is the practice of splitting a large body of content, such as a product catalog or blog archive, across a numbered sequence of separate pages (page 1, 2, 3, and so on), each with its own URL. In SEO it governs how search engines crawl, index, and rank those deeper pages.
prerendering Prerendering is generating a page's full HTML ahead of the request, so crawlers and browsers receive ready-made markup instead of running JavaScript to build it. In SEO it usually means static rendering at build time (SSG); Chrome also uses "prerender" for speculatively loading a likely next page.
product schema Product schema is Schema.org structured data (usually written as JSON-LD) that labels a product's key facts, name, image, price, availability, and reviews, so search engines read them directly instead of inferring them from the page. Google uses it to power product rich results such as price, star ratings, and stock status.
Progressive Web App A progressive web app (PWA) is a website built with standard web technologies that behaves like an installed app: users can add it to a home screen, and with a service worker it can work offline and send push notifications. A web app manifest makes a normal site installable, and a service worker adds the offline and background features.
redirect chain A redirect chain is a sequence of two or more redirects a browser or crawler passes through before reaching the final URL (for example, URL A redirects to B, which redirects to C). Each extra hop adds latency and can weaken or break the SEO signals meant to reach the destination.
redirect loop A redirect loop is a misconfiguration where two or more URLs redirect to each other in an endless cycle, so no request ever lands on a real page. Browsers show ERR_TOO_MANY_REDIRECTS, and Google flags the URL as a "Redirect error" and leaves it out of the index.
render budget Render budget is the informal term for the finite CPU time and compute Google spends executing a page's JavaScript before indexing it. Unlike crawl budget (how many URLs Google fetches), it governs how many JavaScript-dependent pages actually get rendered so their content can be read.
render-blocking resources Render-blocking resources are CSS and JavaScript files a browser must download and process before it can paint any page content. They delay First Contentful Paint and Largest Contentful Paint, slowing how fast users (and Core Web Vitals) see your page.
rendering Rendering is the process of turning a page's HTML, CSS, and JavaScript into the DOM and pixels that browsers display and search engines read. Google renders pages in a headless Chromium during crawling, then uses the rendered HTML to index the content.
rendering queue The rendering queue is the deferred second stage of Google's indexing pipeline where pages that need JavaScript wait for the Web Rendering Service, a headless Chromium, to execute their scripts before the rendered content can be indexed.
rich results Rich results are enhanced Google Search listings that go beyond the standard blue link, adding elements like star ratings, images, prices, or breadcrumbs. Google generates them from structured data (schema.org markup) that describes a page's content and makes the page eligible for the richer display.
Rich Results Test The Rich Results Test is a free Google tool that checks whether a page's structured data qualifies for rich results in Google Search. You submit a live URL or paste code, and it reports which rich result types the page is eligible for, plus any errors or warnings in the markup.
robots exclusion protocol The Robots Exclusion Protocol (REP) is the standard behind robots.txt: rules a site owner publishes to tell automated crawlers which URLs they may or may not fetch. Formalized as IETF RFC 9309 in 2022 (from Martijn Koster's 1994 method), it governs crawling only, not indexing, and is advisory, not an access control.
robots meta tag The robots meta tag is an HTML element in a page's <head> that gives search engines page-level indexing and serving instructions, such as noindex (keep this page out of results) or nofollow (don't follow its links). Unlike site-wide robots.txt, it controls one specific page.
robots.txt robots.txt is a plain-text file placed at the root of a site that tells search-engine crawlers which URLs they may or may not request. It is meant to manage crawler traffic, not to keep pages out of the index.
schema markup Schema markup is structured data added to a web page using the Schema.org vocabulary so search engines and other machines can understand what the content means and, in Google's case, generate rich results such as review stars, product pricing, and recipe cards.
self-referencing canonical A self-referencing canonical is a rel="canonical" link tag whose href points to the page's own URL, signaling that this exact address is the version search engines should index and consolidate duplicate signals onto.
server-side rendering Server-side rendering (SSR) is when the server builds a page's full HTML and sends it to the browser ready-made, instead of shipping an empty shell plus JavaScript that assembles the page in the browser. Users and search engines then get complete content on the first request.
site architecture Site architecture is how a website's pages are organized and connected, from the homepage through category directories down to individual pages, using internal links and URL structure. A clear, shallow hierarchy helps users and search crawlers find, understand, and prioritize your most important content.
sitemap index A sitemap index is an XML file that lists the URLs of multiple child sitemaps. It lets a large site stay within the per-sitemap cap of 50,000 URLs (or 50MB uncompressed): you submit the one index file, and search engines discover every sitemap it references.
soft 404 A soft 404 is a page that returns an HTTP 200 (success) status code while its content tells the user, or Googlebot, that the page does not exist or is empty. Google treats these as errors, keeps them out of search results, and flags them in the Page Indexing report.
Speed Index Speed Index is a lab performance metric that measures how quickly a page's content is visually filled in during load, expressed in seconds. Lighthouse records a video of the page load and scores the visual progression between frames. Lower is better, and it is not a Core Web Vital.
spider trap A spider trap (or crawler trap) is a site structure that catches search crawlers in a near-infinite loop of low-value URLs, like a calendar linking to endless dates or filters generating limitless parameter combinations. It wastes crawl budget and can slow indexing of your real pages.
static site generation Static site generation (SSG) builds every page into finished HTML ahead of time, at build time, then serves those files as-is from a CDN. Because the HTML already exists before the first request, crawlers and users get complete content with no per-request server work and no client-side rendering step.
structured data Structured data is schema.org markup, usually JSON-LD, that labels page meaning for search engines and AI.
Time to First Byte Time to First Byte (TTFB) is the time from when a browser starts requesting a page to when the first byte of the server's response arrives. It includes redirects, DNS lookup, connection and TLS setup, and server processing time. Google rates 0.8 seconds or less as good.
Time to Interactive Time to Interactive (TTI) is a lab performance metric that measures the time from when a page starts loading until it can reliably respond to user input quickly. Google deprecated it and removed it from Lighthouse in version 10 (2023), pointing people to Total Blocking Time and Interaction to Next Paint instead.
Total Blocking Time Total Blocking Time (TBT) is a lab performance metric that measures the total time after First Contentful Paint during which the main thread was blocked long enough to prevent input responsiveness. It is Lighthouse's heaviest-weighted metric and the best lab proxy for the field metric INP.
trailing slash A trailing slash is the forward slash at the end of a URL, as in example.com/page/ versus example.com/page. Google treats the two as separate URLs, so serving identical content on both can create duplicate URLs, with one exception: at the root domain, example.com and example.com/ are equivalent.
URL inspection tool The URL Inspection tool is a Google Search Console feature that reports how Google sees one specific URL: its index status, the canonical Google chose, last crawl date, rendered output and screenshot, and any indexing errors. It also runs a live test and lets you request indexing.
URL parameters URL parameters (query strings) are the key-value pairs added after a question mark in a URL, such as ?color=blue or ?sort=price, that pass instructions to a page. They matter for SEO because they can spawn near-duplicate or faceted URLs that waste crawl budget, split ranking signals, and bloat the index.
URL structure URL structure is how a website's URLs are organized, named, and formatted, from folder hierarchy down to individual word choices. Google recommends simple, readable URLs that use real words, hyphens between words, and a logical path, so that people and crawlers can understand a page from its address alone.
video sitemap A video sitemap is an XML sitemap extended with video-specific tags (thumbnail, title, description, and a player or content URL) for each video on a page, so Google can discover and index video content it might not otherwise find through normal crawling.
viewport meta tag The viewport meta tag is an HTML tag in a page's head that tells mobile browsers how to size and scale the page. The standard value, width=device-width, initial-scale=1, makes content fit the device screen instead of rendering at desktop width and shrinking to fit.
web crawler A web crawler is an automated program that systematically discovers and fetches web pages, following links from one URL to the next. Search engines run crawlers (Google's is Googlebot) to find and read content, then pass it to indexing so pages can appear in search results.
WWW resolve WWW resolve is picking one canonical version of your domain (either www.example.com or example.com) and 301-redirecting the other to it, so users and search engines always land on one address. Browsers treat the two as separate hosts, so consolidating them prevents split ranking signals and duplicate URLs.
x-default x-default is a reserved hreflang value that tells Google which page to serve when a user's language or region settings match none of your site's localized versions. It marks the fallback URL (usually a language selector or global homepage) inside your set of hreflang annotations.
X-Robots-Tag The X-Robots-Tag is an HTTP response header that tells search crawlers how to index or serve a URL, using the same directives as the robots meta tag (noindex, nofollow, and more). Because it lives in the server response, it can also control non-HTML files like PDFs, images, and videos.