Web Development Glossary

An API (Application Programming Interface) is a way for software systems to talk to each other.
It defines what data you can request, what you’ll receive, and how to send the request.
For example, a website might call an API to fetch product prices or user details, rather than storing that information directly on the page.

Read more on Bespoke API Integrations

Azure is Microsoft’s cloud computing platform for building, hosting, and managing applications.

It provides services like servers, databases, storage, and security without needing to run physical hardware.

That’s why teams can scale websites and software quickly, only pay for what they use, and deploy updates more reliably.

Website accessibility means designing and building websites so everyone can use them, including people with disabilities.

This includes support for screen readers, keyboard navigation, clear contrast, and readable content.

Request a website accessibility audit 

Agile development is a way of building software in small, iterative stages instead of one large release.

Teams regularly plan, build, test, and review their work in short cycles called sprints.

That’s why Agile helps teams adapt to change, deliver value faster, and improve software based on real feedback.

Read our latest blog on Agile Methodology 

An algorithm is a set of rules or steps used to solve a problem or complete a task.

In software, it defines how data is processed to produce a result.

That’s why algorithms power everything from search results and recommendations to sorting data and detecting patterns.

Asynchronous processing allows tasks to run without blocking other operations. For example, it can fetch data from an API in the background while the rest of the page stays usable. 

That’s why modern websites can keep responding to clicks, scrolling, and input even while content is still loading behind the scenes.

A breadcrumb is a navigation element that shows where you are in a site’s hierarchy, usually as a short trail of links like:

Home > Category > Page

It improves usability, allowing users to jump back to higher-level pages without relying on the browser’s back button. 
Breadcrumbs are especially useful on larger sites where content is organised into multiple layers.

A web browser is software that lets you visit websites and view their content. It takes the code behind a page, mainly HTML for structure, CSS for styling, and JavaScript for interactivity, and turns it into something you can read, click, and interact with.

In short, these applications act as the bridge between a website’s files and what appears on your screen.

A payload is the actual content inside a request or response when systems communicate, especially through an API. It’s the part that carries the useful information, like the JSON data you send when creating a new user, or the results you receive back when fetching a list of products.

In short, the payload is what’s being passed between the client and server, not the surrounding headers or metadata.

Backend development is the work that happens behind the scenes to make a website or app function properly.

It covers things like servers, databases, authentication, and the business logic that decides what happens when someone logs in, submits a form, or makes a purchase.

If the front end is what people interact with, the backend is the part that makes those interactions reliable, secure, and connected to real data.

A backup is a recoverable copy of important data, saved so it can be restored later if needed.

Depending on the system, it might include databases, uploaded files, source code, configuration settings, and sometimes even full server images.

The practical goal is simple: if something breaks or data is lost, you have a known “good” point you can roll back to.

Bootstrap is a front-end framework that provides ready-made CSS and JavaScript components for building websites.

It includes a responsive grid system, common UI elements (like buttons and forms), and consistent styling patterns you can apply quickly.

Teams often use it when speed and consistency matter more than designing every component from scratch.

Beta testing is a stage where software is tested by real users in real conditions before a full public release.

It sits after internal testing, and it’s usually focused on catching edge cases, usability issues, and unexpected behaviour that only shows up outside a controlled environment.

The feedback from beta tends to drive final fixes and small refinements, rather than big feature changes.

A bug is a defect in software that causes it to behave differently from what was intended.

It can be obvious, like a broken button, or subtle, like an occasional calculation error that only appears with certain inputs.

Bugs are usually tracked, reproduced, and fixed in a structured way so the same issue does not keep resurfacing.

A CMS, or Content Management System, is software that allows people to create and update website content without writing code.

It usually provides an admin interface for managing pages, images, and other content in one place.

Systems like Umbraco or Agility separate content from code, which makes day-to-day updates quicker and less dependent on developers.

Read more about web CMS development 

Caching is the practice of storing data temporarily so it can be accessed faster next time.

Instead of generating the same response continually, a cached version is served when nothing has changed.

This reduces server workload and helps pages load more quickly, especially during busy periods.

A CTA, or call to action, is a prompt that encourages a user to take a specific step.

It might be a button, link, or short piece of text such as “Contact us” or “Download the guide”.

Clear CTAs help guide users through a site and make it easier for them to know what to do next.

Contact us today

CSS, or Cascading Style Sheets, controls how a website looks rather than how it works.

It defines things like layout, colours, fonts, spacing, and how pages adapt to different screen sizes.

By keeping styling separate from content, CSS makes design changes easier to manage and apply consistently.

Cloud hosting runs websites and applications on a network of connected servers instead of a single physical machine.

Resources such as storage and processing power can be scaled up or down based on demand.

This approach improves reliability and flexibility, since traffic spikes or hardware failures are less likely to take a site offline.

Cookies are small pieces of data stored in a user’s browser by a website.

They can be used to remember preferences, keep users signed in, or track activity across sessions.

Because cookies can store personal information, their use is often regulated by privacy and consent rules.

Client-side refers to code that runs in the user’s browser rather than on the server.

This includes things like interface interactions, form validation, and dynamic page updates.

Client-side processing can make websites feel faster and more responsive, since not every action requires a server request.

A component is a reusable piece of a website or application.

It might be a button, form, navigation menu, or any self-contained UI element with its own structure and behaviour.

Using components helps teams build and maintain interfaces more efficiently, as the same piece can be reused and updated in one place.

A Content Delivery Network, or CDN, is a system that stores and serves site assets from multiple servers in different regions, rather than relying on a single origin server. 

When someone visits your site, the CDN delivers files, including images, scripts, and stylesheets from the server closest to them, which helps pages load faster and reduces strain on the main host. 

A cipher is an algorithm that transforms readable data into an encrypted form, and then back again when the right key is provided. 

This type of algorithm is a core part of modern security, especially for protecting information sent over the internet, such as login details, personal data, or payment information. Without ciphers, most everyday web communication would be far easier to intercept or tamper with.

A domain is the human-readable address used to access a website on the Internet.

It maps to an underlying IP address so browsers know where to send requests.

For example, in the URL: https://www.i-finity.co.uk/services/azure-cloud-hosting-services-support

The domain is: i-finity.co.uk

This separation between the domain and the rest of the URL allows websites to change hosting or structure without altering their main address.

A database is a structured system for storing and retrieving data.

It organises information so it can be searched, updated, and managed efficiently, even at large scale.

Web applications rely on databases for things like user accounts, content, transactions, and system settings.

Deployment is the process of making new or updated software available in specific environments these can typically be staging/test environment, pre-production and production which is the live environment.

It can involve moving code to servers, running setup scripts, and applying configuration changes.

In practice, deployment marks the point where changes move from development into real use.

Debugging is the process of finding and fixing errors in software.

It usually involves reproducing the problem, inspecting logs or code, and testing possible causes one step at a time.

The aim is not only to resolve the immediate issue, but to understand why it happened so that similar problems can be avoided. 

A data packet is a small chunk of information that travels over a network as part of a larger message. Instead of sending everything in one continuous stream, networks split data into packets so each piece can be routed, checked, and re-sent if needed. 

An ecommerce platform is software used to sell products or services online.

It typically handles things like product listings, payments, orders, and customer accounts in one system.

Umbraco Commerce provide the core functionality to integrate with 3rd party ecommerce platforms, often design and features can be customised to suit different businesses.

Encryption is the process of converting data into a coded form so it cannot be read without the correct key.

It is used to protect sensitive information while it is stored or being transmitted.

Without encryption, data such as passwords or payment details could be intercepted and understood by unauthorised parties.

An embed is content from one source that is displayed inside another website or application.

Examples include videos, maps, or social posts that appear within a page but are hosted elsewhere.

The embedded content stays linked to its original source, which means updates or changes are reflected automatically.

An extension or plug-in is an add-on that expands the functionality of existing software.

It is installed to introduce new features or modify behaviour without changing the core system.

Content management systems and browsers commonly use extensions or plug-ins to add capabilities as needed.

A favicon is a small icon linked to a website, usually shown in the browser tab, bookmark lists, and sometimes in search results or shortcuts. 

It acts as a quick visual marker for the site, which helps users spot it faster when they have multiple tabs open or a long list of saved pages.

Full-stack web development means building web applications across both the front end and the back end, so you are working on what people see and use, as well as what happens behind the scenes.

It usually involves:

• Front end (client side): layouts, UI components, forms, and the JavaScript that drives interactive behaviour.
• Back end (server side): APIs, databases, authentication, and the business logic that processes requests.
• Deployment and upkeep (sometimes): pushing changes live, monitoring performance, and keeping the application stable.

Explore our custom software development services

GitHub is a platform for storing, managing, and collaborating on code.

It uses version control to track changes, allowing teams to work on the same project without overwriting each other’s work.

Developers rely on GitHub to review updates, manage issues, and maintain a clear history of how a codebase evolves.

Geolocation is the process of identifying a user’s approximate location using digital signals.

Websites and applications often use IP addresses, GPS data, or device settings to determine this information.

Location data can then be used to tailor content, services, or functionality based on where a user is accessing a site from.

A GIF is an image format that supports simple animation.

It plays a short sequence of frames in a loop, without requiring video controls or sound.

GIFs are commonly used to show brief interactions, visual feedback, or lightweight animations within web pages.

A hash function takes some input data and produces a fixed-length output, often called a hash value or digest. Even a small change in the input usually results in a very different hash, which makes hashing useful for checking whether data has been altered.

Hash functions are often used for things like storing passwords securely, verifying file downloads, and confirming that data has not been tampered with during transfer.

A host is the server, platform, or provider that keeps a website or application online and makes it accessible to visitors. 

It stores the site’s files and data, then serves them when someone types in the URL or loads a page. 

In practice, hosting can range from a simple shared server to cloud services that scale up as traffic increases.

HTML5 is the current version of HTML used to structure pages on the web. It brought in several improvements that make modern sites easier to build and more consistent to use:

• Cleaner, more semantic elements for describing pages, like <header>, <nav>, and <article>.
• Native support for multimedia, including video and audio, plus richer interactive content without relying on plugins.
• Improved accessibility, making it easier to create pages that work well with screen readers and assistive tools.

HTTP, short for Hypertext Transfer Protocol, is the set of rules that allows browsers and servers to communicate on the web. It’s what makes it possible to request a page, send form data, or fetch information from an API, and then receive a response back. 

HTTP defines how those requests and responses are structured, including things like the URL being requested, the method used (such as GET or POST), and any headers or data sent along with the message.

TLS, short for Transport Layer Security, is a security protocol that encrypts data while it travels between a user’s device and a server. 

This security layer helps prevent eavesdropping and tampering, which is why it’s used to protect sensitive information such as login credentials, payment details, and personal data. 

An I-Frame or iframe - short for inline frame - is an HTML element used to display one webpage inside another.

It allows external content, such as videos, maps, or third-party tools, to appear within a page without being hosted there.

I-Frames are often used when content needs to remain separate while still being visible to users.

Information architecture is the way content is structured and organised within a website or application.

It covers navigation, page hierarchy, and how information is grouped and labelled.

Good information architecture makes it easier for users to find what they need and understand where they are within a system.

Image optimisation is the process of preparing images so they load quickly without unnecessary loss of quality.

This can involve resizing, compressing files, and choosing the right formats for different devices.

Well-optimised images improve performance, reduce data usage, and help pages feel faster and more responsive.

JavaScript is a programming language that lets websites do more than display static content. It adds interactive behaviour and dynamic functionality, like updating a page without reloading, validating forms, or responding to clicks and user input. 

In modern web development, it’s one of the core technologies used to build rich, app-like experiences in the browser.

JSON, which stands for JavaScript Object Notation, is a lightweight format for storing and exchanging data.

It represents information using simple key and value pairs that are easy for both humans and machines to read.

Because JSON is widely supported, it is commonly used to send data between servers, APIs, and web applications.

Lazy loading is a technique where content is only loaded when it is needed.

For example, images or videos may load as a user scrolls down a page rather than all at once.

This approach reduces initial page weight and helps important content appear sooner.

Load balancing is the process of distributing traffic across multiple servers.

Instead of sending every request to one machine, requests are spread out to avoid overload.

This helps maintain performance and availability, even during traffic spikes or server failures.

Load time refers to how long it takes for a webpage or application to become usable.

It can include the time needed to fetch data, load assets, and render content in the browser.

Shorter load times improve user experience and reduce the chance of users abandoning a page.

A markup language is a way of adding structure and meaning to content using tags. Those tags tell a computer how different parts of the content should be organised, like headings, paragraphs, links, or lists. 

The best-known example is HTML, which is used to structure pages on the web.

Mobile-first design and development is an approach where websites and applications are designed for smaller screens before being adapted for larger ones.

The process prioritises essential content, performance, and usability on mobile devices from the outset.

By starting with mobile constraints, teams often end up with cleaner layouts and experiences that scale more effectively across all screen sizes.

Middleware is software that sits between different parts of an application, or between separate services, and helps them work together. It handles the plumbing that makes communication reliable, such as routing requests, transforming data, and managing sessions. 

Middleware is also where you often add cross-cutting concerns like authentication, logging, rate limiting, and other security controls, so those checks happen consistently before the request reaches the main application logic.

MVC, short for Model View Controller, is a design pattern that splits an application into three parts. The Model handles the data and business logic, the View controls what the user sees, and the Controller connects the two by responding to user actions and updating the model or view as needed. 

Keeping those layers separate makes code easier to organise, test, and maintain, especially as the application grows.

A minimum viable product, often shortened to MVP, is an early version of a product built with only the features needed to be usable.

It is released so teams can test an idea, gather feedback, and see how people actually use it.

Instead of aiming for completeness, an MVP focuses on learning early and shaping the product based on real behaviour rather than assumptions.

A multi-site setup means running multiple websites from a single instance of a CMS.

In platforms like Umbraco, this allows different websites to share one back office while keeping their own designs, content structure, and page hierarchies.

This approach is often used when organisations want centralised management without forcing every site to look or behave the same.

A native app is an application built specifically for a particular operating system or device type.

It is developed using the tools and languages intended for that platform, such as Swift for iOS or Kotlin for Android.

Because native apps run directly on the device, they can take full advantage of system features like performance, hardware access, and offline use.

Node.js is a free, open-source, cross-platform JavaScript runtime that lets developers run JavaScript outside the browser, including on servers. It’s widely used to build web applications and APIs, and it can also power command-line tools and automation scripts.

Because Node.js is event-driven and designed to handle many requests efficiently, it’s often a good fit for scalable applications, especially those that deal with lots of real-time or data-heavy interactions.

Open source refers to software whose source code is publicly available to view, use, and modify.

This allows developers to adapt the software to their own needs or contribute improvements back to the project.

Open source projects are often maintained by a mix of individuals and organisations, with changes reviewed openly rather than controlled by a single vendor.

Optimising a website involves improving how it performs, how it’s found, and how it’s used.

This can include speeding up load times, refining content and structure, and ensuring the site works well across devices.

The goal is to remove friction, so users can access information quickly and search engines can understand the site more effectively.

Object-oriented programming is a way of writing software that models a system as a set of objects, each combining data with the functions that work on it. It’s built around ideas like encapsulation, inheritance, polymorphism, and abstraction, which help keep code modular and easier to extend as a project grows.

OpenGL, short for Open Graphics Library, is a graphics API used to render 2D and 3D visuals. 

It provides a standard set of commands that software can use to work with a device’s graphics hardware, which is why it has been widely used in areas like games, simulations, and visualisation tools. OpenGL is increasingly replaced by APIs like Vulkan, Metal, and WebGPU in modern development. 

A pixel is the smallest individual unit of a digital image or screen display.

Screens are made up of thousands or millions of pixels arranged in a grid, each showing a specific colour.

The number and density of pixels influence how sharp and detailed an image or interface appears.

Website performance refers to how efficiently a site loads and responds to user interaction.

It covers factors such as speed, stability, and how smoothly pages render across devices and connections.

Performance is often assessed through real usage metrics, rather than just how fast a page loads on paper.

A prototype is an early model used to explore how a web application might work.

It can range from simple wireframes to interactive versions that simulate key features.

Prototypes are typically used to test ideas, flows, and assumptions before committing to full development.

A public key is one half of a cryptographic key pair used in public key encryption. It can be shared openly and is used to encrypt data or verify a digital signature, while the matching private key is kept secret and is used to decrypt or sign. 

This setup makes it possible to secure communications without both sides needing to share the same secret key in advance.

A RESTFul API is a way for applications to exchange data using standard web requests, typically over HTTP. It usually works by exposing URLs, called endpoints, that you can interact with using methods like GET, POST, PUT, and DELETE. 

RESTFul APIs are widely used because they follow consistent conventions, which makes them easier to understand, integrate, and scale across different systems.

Read more about bespoke API Integrations. 

A code repository is a central place where source code is stored and managed.

It keeps track of files and changes over time, making it possible to collaborate without losing work.

Repositories are commonly used with version control systems, which allow teams to review updates, roll back changes, and maintain a clear project history.

Robots.txt is a simple text file on a website that tells search engine crawlers which pages or sections they are allowed to access. It sits in the site’s root directory and guides what should be crawled or ignored.

It’s important to note that robots.txt is an instruction, not a security measure, since well-behaved crawlers follow it, but it doesn’t stop access to the pages themselves.

Replatforming involves moving a website or application from one underlying platform to another.

This might include changing a CMS, ecommerce system, or hosting environment while keeping much of the existing content or functionality.

The process usually focuses on improving performance, scalability, or maintainability, rather than rebuilding everything from scratch.

Software as a service, often shortened to SaaS, is software that is accessed online rather than installed on a local device.

The application is hosted and maintained by a provider, with users typically accessing it through a browser.

Updates, security, and infrastructure are handled centrally, which reduces the need for local setup or ongoing maintenance.

SSL is a security technology that encrypts data sent between a user’s browser and a website.

It ensures that information such as login details or payment data cannot be read if intercepted.

Websites using SSL can be identified by “https” in the address bar, which signals that the connection is protected.

A sub-domain is an additional part added to a main domain to organise or separate content.

Sub-domains are often used to structure websites, for example, to separate content areas, applications, or environments without changing the core domain.

Let’s take our domain of: www.i-finity.co.uk 

An example subdomain could be www.support.i-finity.co.uk

Search engine optimisation (SEO) is the practice of improving a website so it appears more prominently in search results on Google and other engines. 

It typically includes:

• Content optimisation: writing and structuring pages around search intent.
• Technical SEO: site speed, crawlability, indexing, and structured data.
• On-page SEO: titles, headings, internal links, and metadata.
• Authority building: earning quality backlinks and strengthening trust signals.

Serialisation is the process of converting data into a format that can be stored or sent somewhere else, then reconstructed later. 

For example, an object in memory might be serialised into JSON or XML so it can be transmitted through an API, saved to disk, or placed in a message queue.

Server-side rendering (SSR) is a technique where a web page is generated on the server and sent to the browser as ready-to-display HTML. 

Because the first version of the page arrives already rendered, it can improve initial load speed and make content easier for search engines to crawl. 

SSR is often compared to client-side rendering, where the browser builds most of the page using JavaScript after the initial load.

A URL slug is the readable part of a web address that identifies a specific page, usually the last section of the path. 

For example, in this URL: ‘https://www.i-finity.co.uk/services/azure-cloud-services’, the slug is ‘azure-cloud-services’. 

Slugs are often based on the page title and are designed to be clear for users and search engines.

Two-factor authentication, often called 2FA, adds an extra step to the login process.

Alongside a password, users must provide a second form of verification, such as a code sent to their phone or generated by an app.

This reduces the risk of unauthorised access if a password is compromised.

Two-factor authentication, often called 2FA, adds an extra step to the login process.

Alongside a password, users must provide a second form of verification, such as a code sent to their phone or generated by an app.

This reduces the risk of unauthorised access if a password is compromised.

A template or theme defines the visual layout and styling of a website or application.

It controls elements such as page structure, typography, colours, and reusable components.

Using templates or themes helps maintain consistency across pages while allowing content to change independently.

UI stands for User Interface and refers to the visual elements people interact with on a website or app.

UX stands for User Experience and focuses on how those interactions feel, including ease of use, clarity, and flow.

While UI is about appearance and controls, UX considers the overall experience of moving through a product.

User acceptance testing, or UAT, is the stage where software is tested by end users before final release.

It checks whether the system behaves as expected in real scenarios, rather than just whether it works technically.

UAT helps confirm that requirements have been met and that the product is ready to go live.

Umbraco is a content management system used to build and manage websites.

It provides a flexible editing interface and allows developers to structure content in a way that fits the project.

Umbraco is often chosen when teams need control over design and functionality without locking content editors into rigid templates.

The viewport is the visible area of a user’s screen where a webpage is displayed.

Its size changes depending on the device, window size, and screen orientation.

Design and layout decisions are often made with the viewport in mind so content adapts correctly across different screens.

Version control is a system for tracking changes to files over time.

It allows multiple people to work on the same codebase while keeping a record of what changed and when.

If something goes wrong, earlier versions can be reviewed or restored without losing all progress.

Form validation is the process of checking user input before it is accepted or submitted.

It ensures required fields are completed and that data follows the expected format, such as a valid email address.

Validation helps prevent errors, improves data quality, and gives users clear feedback when something needs fixing.

Web application development is the process of creating interactive, browser-based software, including things like portals, dashboards, booking tools, and online stores. 

Unlike static websites, web applications respond to user input, handle data, and often connect to databases or APIs to deliver personalised or real-time functionality.

A web crawler is an automated program that search engines use to discover websites and gather information from their pages. It follows links across the web, reads the content it finds, and sends that information back so the search engine can add it to its index. 

Crawlers are a key part of how pages end up appearing in search results, and they usually follow rules set by sites, such as robots.txt, to understand what should or should not be crawled.

WebP is an image file format developed to reduce file sizes without a noticeable loss in quality.

It supports both still images and simple animation, as well as transparency.

WebP is often used on websites to improve load times while keeping images looking sharp.

An XML sitemap is a file that lists the pages of a website in a structured format.

It helps search engines understand which pages exist and how they are organised.

Sitemaps are used to support crawling and indexing, particularly for larger or frequently updated sites.