The web development glossary, written by engineers who actually ship.

A 301 redirect is a permanent HTTP redirect that transfers a URL's ranking signals to a new destination.

AEO is a content optimization practice that structures pages so AI-powered answer engines can extract and cite them directly.

AI crawlers are web bots that scrape and index content to train or power large language models.

Astro is a web framework that ships zero JavaScript by default and uses island architecture for partial hydration.

AVIF is an image format based on AV1 video codec that delivers superior compression at high visual quality.

A canonical URL is an HTML element that tells search engines which version of a duplicate page is the preferred one to index.

CrUX is a public dataset of real-user performance metrics collected from opted-in Chrome browser sessions.

Client-Side Rendering (CSR) is a web architecture pattern where the browser builds the page's HTML using JavaScript after the initial page load.

Code splitting is a performance technique that breaks JavaScript bundles into smaller chunks loaded on demand.

A component library is a collection of reusable UI elements packaged for consistent use across applications.

Content modeling is the practice of defining structured content types, fields, and relationships for a CMS.

Contentful is a headless CMS that delivers structured content via API to any frontend or channel.

Core Web Vitals are Google's three standardized metrics that measure real-user page loading, interactivity, and visual stability.

Crawl budget is the number of pages a search engine will crawl on your site within a given timeframe.

CSS Custom Properties are author-defined values declared with `--` syntax that enable reusable, dynamic styling in stylesheets.

Cumulative Layout Shift (CLS) is a Core Web Vital that measures the total unexpected visual movement of page elements during loading.

A design system is a collection of reusable components, tokens, and guidelines that enforce consistent UI across products.

Design tokens are named values that store visual design decisions like color, spacing, and typography for consistent multi-platform use.

Directus is an open-source headless CMS that wraps any SQL database with a REST and GraphQL API.

A feature flag is a conditional toggle that controls feature visibility in production without deploying new code.

Figma Variables are reusable design values (colors, numbers, strings, booleans) that enable dynamic theming and prototyping in Figma.

First Contentful Paint (FCP) is a performance metric that measures the time until the browser renders the first piece of DOM content.

Google AI Overview is a SERP feature that displays AI-generated summary answers above traditional organic results.

GPTBot is OpenAI's web crawler that scrapes content to train GPT models and power ChatGPT responses.

Headless WordPress is a CMS architecture that uses WordPress for content management while delivering content via API to a decoupled frontend.

Hreflang is an HTML attribute that tells search engines which language and region a page targets.

Image optimization is a set of techniques that reduce image file size and improve page load performance.

Interaction to Next Paint (INP) is a Core Web Vital that measures a page's overall responsiveness to user interactions.

JSON-LD is a linked data format that embeds structured metadata into web pages using JSON syntax.

Largest Contentful Paint (LCP) is a Core Web Vitals metric that measures how fast the largest visible element renders on a page.

Lighthouse is an open-source auditing tool by Google that scores web page performance, accessibility, SEO, and best practices.

llms.txt is a proposed text file that tells large language models how to read and represent a website's content.

A meta description is an HTML element that provides a brief summary of a page's content for search engine results.

Next.js is a React framework that provides server rendering, routing, and full-stack capabilities out of the box.

Nuxt is a Vue.js meta-framework that provides server-side rendering, static generation, and file-based routing out of the box.

Pages Router is the original Next.js routing system that maps files in the /pages directory to URL routes.

PageSpeed Insights is a Google tool that measures web page performance using Lighthouse and real-user CrUX data.

Partial hydration is a rendering strategy that selectively adds JavaScript interactivity to specific components on an otherwise static page.

Passage ranking is a Google search feature that indexes and ranks individual passages within a page independently.

Payload CMS is a self-hosted, headless content management system built on Node.js with a code-first configuration approach.

A pillar page is a long-form content hub that covers a broad topic and links out to related cluster pages.

Programmatic SEO is a pattern that generates large volumes of search-optimized pages from structured data and templates.

React Server Components are a React architecture that renders components on the server, sending only their output to the client.

A redirect map is a structured lookup table that pairs old URLs with their new destinations during site migrations.

Replatforming is a migration strategy that moves a website or application from one technology stack to another.

robots.txt is a plain-text file at a site's root that tells web crawlers which URLs they may or may not request.

sameAs is a Schema.org property that links an entity to its authoritative profiles across the web.

Sanity Studio is an open-source, React-based CMS editing interface for the Sanity content platform.

Schema.org structured data is a standardized vocabulary that helps search engines understand and display web content.

SEO Preservation is a migration discipline that maintains search rankings, traffic, and link equity during a site redesign or platform change.

Server-Side Rendering (SSR) is a web architecture pattern that generates HTML on the server for each incoming request.

A Sitecore replacement is a CMS migration strategy that moves enterprise sites off Sitecore to a modern, often headless, platform.

SolidJS is a declarative JavaScript UI framework that uses fine-grained reactivity for DOM updates without a virtual DOM.

Static Site Generation (SSG) is a build-time rendering strategy that pre-generates HTML pages before deployment.

Strapi is an open-source headless CMS that provides a customizable API layer for content management.

Tailwind CSS is a utility-first CSS framework that lets you style elements directly in markup using predefined classes.

Time to First Byte (TTFB) is a web performance metric that measures the duration between a browser's request and the first byte of the server's response.

A topic cluster is an SEO content architecture that groups related pages around a central pillar page via internal links.

A traditional CMS is a coupled content management system that handles both content editing and front-end rendering in a single application.

Vue.js is a progressive JavaScript framework that builds user interfaces through a reactive, component-based architecture.

WebP is a lossy and lossless image format by Google that delivers smaller file sizes than JPEG and PNG.

WordPress is a PHP-based content management system that powers over 40% of all websites on the internet.

WordPress to Next.js migration is the process of moving a WordPress site to a Next.js frontend, often retaining WordPress as a headless CMS.

An XML sitemap is a structured file that lists a website's URLs to help search engines discover and crawl pages efficiently.