J 10 / 26
Web Encyclopedia

Understanding the web,
in plain English.

JavaScript, JSON-LD — the J-words powering interactivity and structured data on the web.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
01

JavaScript

JavaScript is a programming language that runs directly in the browser, making web pages interactive and dynamic. It powers menus that open and close, forms that validate input in real time, image sliders, maps, animations, and any content that changes without reloading the page. Modern web applications like Google Docs or Notion are built almost entirely in JavaScript.

Real-world example

If HTML is the walls and furniture of a room (structure) and CSS is the décor (appearance), JavaScript is the electricity: it makes the lights switch on, the doors open automatically, and the music play.

Why it matters for you

A website without JavaScript is static and passive. JavaScript enables the interactive experiences — booking systems, chatbots, personalised content — that turn a brochure site into a genuine business tool.

Build an interactive website
02

JSON-LD (Structured Data)

JSON-LD is a format for embedding structured data into your web pages so that Google understands your content more precisely. It can tell Google that a page is a product (with price and availability), a recipe (with ingredients and cooking time), a business (with opening hours), or an FAQ — enabling rich results in search.

Real-world example

JSON-LD is like attaching a well-completed information sheet to your website. Instead of Google having to guess what your content means, you tell it explicitly: 'This is a product, it costs £49, and it is in stock.'

Why it matters for you

Pages with JSON-LD structured data are eligible for rich snippets in Google results — star ratings, FAQs, prices, and more. These enhanced listings get significantly more clicks than standard results, often dramatically improving CTR without changing your ranking position.

Add structured data to my site
03

JavaScript SEO

JavaScript SEO refers to the practice of ensuring that content rendered via JavaScript is correctly discovered, crawled, and indexed by search engines. Unlike static HTML, JavaScript-generated content requires Googlebot to execute the script — a second, deferred rendering step that can delay or prevent indexation if not handled correctly.

Real-world example

A React-built e-commerce site renders product descriptions client-side. Googlebot never waits for the JavaScript to execute, indexing blank pages instead. After migrating to server-side rendering, product pages appear in Google results within 48 hours.

Why it matters for you

If your site uses a modern JavaScript framework, invisible rendering issues could be silently blocking your rankings. A technical SEO audit will surface JS-related indexation gaps before they cost you traffic.

Audit my technical SEO
04

Joomla

Joomla is an open-source Content Management System (CMS) — the world's third most popular, after WordPress and Drupal. It powers approximately 2% of all websites and is particularly well-suited for complex membership sites, community portals, and multilingual websites. Joomla offers more built-in functionality than WordPress but requires more technical knowledge to set up and maintain.

Real-world example

A professional association manages 3,200 member profiles with different access levels, a member directory, event registration, and a multilingual front-end in French, English, and Spanish — all built on Joomla without custom development. The same functionality in WordPress would require multiple third-party plugins and significant configuration.

Why it matters for you

Understanding which CMS your website uses helps you plan its evolution, find qualified developers, and estimate maintenance costs. Joomla sites have different strengths and vulnerability profiles to WordPress — knowing the difference prevents costly migration decisions based on incomplete information.

Migrate or rebuild my website
05

Jamstack

Jamstack is a modern web architecture based on pre-built static files (HTML, CSS, JS) served via a CDN, with dynamic functionality added through APIs and JavaScript on the client side. The name comes from JavaScript, APIs, and Markup. Unlike traditional CMS websites that generate pages on-the-fly from a database, Jamstack sites pre-render all pages at build time — delivering near-instant load speeds and exceptional security (no database to hack).

Real-world example

A restaurant's website built on Jamstack (using Gatsby + Netlify) scores 98/100 on Google PageSpeed, loads in 0.8 seconds globally, has never had a security breach, and costs £8/month to host. A comparable WordPress site on shared hosting scores 41/100, loads in 4.2 seconds, and requires weekly plugin updates for security.

Why it matters for you

Jamstack sites offer exceptional performance, security, and hosting cost advantages for sites with relatively stable content. For businesses prioritising speed, scalability, and minimal maintenance overhead — particularly brochure and portfolio sites — it is increasingly the architecture of choice.

Build a high-performance site
06

jQuery

jQuery is a fast, lightweight JavaScript library first released in 2006 that dramatically simplifies HTML DOM manipulation, event handling, animation, and AJAX interactions. It became the most widely used JavaScript library on the web, appearing on an estimated 75% of all websites at its peak. While modern JavaScript frameworks (React, Vue) have reduced jQuery's dominance in new projects, it remains embedded in millions of legacy sites and popular CMS platforms including WordPress.

Real-world example

A WordPress site loads jQuery from a CDN on every page — even pages with no interactive elements — adding 87KB and 120ms to every page load. After an audit identifies jQuery as a render-blocking resource, the developer defers it on non-interactive pages. Page load time improves by 0.4 seconds, and Google's PageSpeed score rises from 67 to 84.

Why it matters for you

Many websites (particularly older WordPress sites) carry jQuery as unnecessary bloat — loading it even on pages that don't need it. Understanding what jQuery does, and whether your site actually uses it, is an important step in any performance audit.

Audit my website performance
07

JSON (JavaScript Object Notation)

JSON (JavaScript Object Notation) is a lightweight, human-readable data format used to transmit structured information between applications and APIs. It represents data as key-value pairs in a simple text format that any programming language can parse. JSON is the dominant format for web APIs, configuration files, and data exchange — powering everything from Google Maps integrations to CRM synchronisation and AI tool connections.

Real-world example

When a visitor submits a contact form on your website, the form data is sent to your server as a JSON object: {"name": "Sarah Jones", "email": "sarah@company.com", "message": "I'd like a quote"}. The server parses this, stores it in your CRM, and sends a confirmation email — all through JSON-formatted messages between applications.

Why it matters for you

You don't need to write JSON yourself, but understanding that it's the universal language your web applications use to talk to each other helps you make informed decisions about integrations, API connections, and troubleshooting data flow issues between your digital tools.

Automate my business workflows