Front-End Development: The Complete Guide

What Is Front-End Development?

Front-end development primarily focuses on user experience. Using the related coding and design techniques, you as front-end developers build the elements of an application that are directly accessed by end-users with a goal of rendering the entire interface elegant, easy to use, fast, and secure, fostering user engagement and interaction.

Thanks to the latest design and technology trends geared for the front end, you can build increasingly more sophisticated designs and interaction patterns. Simultaneously, however, more complexity results, so much so that front-end development has become a specialized field that requires deep expertise.

The major trend in front-end development in recent years is the growth of applications for mobile and smart devices, with users accessing applications from a growing number of devices with different screen sizes and interaction options. As a result, front-end developers must ensure their application delivers a consistent, high-quality user experience for all devices and usage scenarios. That’s a daunting challenge.

This article covers the following topics:

Front-End Development Versus Back-End Development

Hardware, computer programs, and websites comprise many components: code, databases, user interfaces (UI). Those that interact with users are in the front end; those that operate the technology are situated in the back end, also called the data-access layer. The back end provides the resources to support the front end.

Here are the key differences between software development in the front end and back end:

  • Back-end development is the process of building the components for running the application behind the scenes. Examples are components for data storage, infrastructure, integration with external systems, and code written in one or more programming languages. Users cannot access the back end.
  • Front-end development is the process of building components that interact with users. Examples are the user interface, buttons, user-entered data, websites, and user experience (UX) features. The front end aims at meeting user requirements and delivering a positive user experience.

Programming Languages for Front-End Development

Below are the most common programming languages for developing the front end.

HTML

The HyperText Markup Language (HTML) programming language, which defines the structure and meaning of web content, is a building block for front-end development. Through HTML, browsers display text or load elements, rendering webpages, which contain hyperlinks and links to other webpages, for users.

CSS

Cascading style sheets (CSS) is the standard language that specifies how to display HTML content: fonts, foreground and background colors, etc. With CSS, you can control the design layout and its components for various devices like desktops, tablets, and smartphones. Examples of the components are the header, body, footer, content, asides, and sections.

For more details, see Working With CSS Images.

JavaScript

JavaScript (JS) extends the functionality of websites beyond HTML and CSS. Through JS:

  • Webpages can refresh themselves dynamically and respond to user actions without page reloads or other changes.
  • You can model animated UI components, such as pop-ups, image sliders, and extensive navigation menus.

Front-End Development Frameworks

Front-end frameworks accord you ready-made code and components, such as prewritten standard functions packaged as libraries, with no need to build common functionality and components from scratch.

Angular

With Angular, a popular, open-source JavaScript framework initially created by Google, you can deliver highly dynamic results through the HTML syntax. Angular adopts an efficient modular approach and follows the MVC architecture, which divides the website structure into three parts: model, view, and controller (MVC). In particular, Angular facilitates cleaner code through TypeScript and leverages the dependency-injection design pattern.

React

Introduced in 2011 by Meta and now supported by a large community, React is an open-source, declarative JavaScript framework whose component-based approach enables code reuse. React facilitates more efficient updates of views with the virtual Document Object Model (VDOM), a lightweight JavaScript representation of the DOM, enhancing performance. You can use React to develop single-page applications (SPAs).

jQuery

Widely used and supported by many user-created plugins, jQuery is an open-source JavaScript library that simplifies the development of web applications. For example, jQuery edits CSS properties by incorporating JavaScript functionalities and applies effects, such as fade-in and fade-out, to website elements. With jQuery, you can also simplify the processes of implementing HTML DOM changes, event handling, and Asynchronous JavaScript and XML (Ajax).

Vue.Js

Written in JavaScript, Vue.js is a core library that focuses on the view layer only, enabling the development of distinct web interfaces and single-page applications. You can integrate this library with other tools and libraries for the desired output.

Bootstrap

A popular, open-source framework for developing responsive and mobile-first websites, Bootstrap offers CSS-based and JavaScript-based templates that include components like navigation bars, progress bars, thumbnails, and dropdowns, all of which you can incorporate into webpages.

Bootstrap implements responsive images through built-in code that automatically resizes them according to the current screen size. Also, with the JQuery plugins in Bootstrap, you can build and deliver interactive solutions for modal popups, image carousels, and transitions.

Semantic UI

A well-documented development framework for creating responsive layouts with HTML, Semantic UI relies on the semantic language to facilitate development and offers components for various features. You can integrate Semantic UI with many third-party applications and tools.

Svelte

Svelte is a compiler that converts declarative components into highly optimized vanilla JavaScript that surgically updates the DOM during the build phase of the development process. That’s a different approach from that in frameworks like Vue and React, which work in users’ browsers while the applications are running.

Preact

Preact offers a thin VDOM abstraction, registers real event handlers, builds on stable platform features, and integrates with other libraries. You can use Preact directly in browsers without transpilations.

Preact is so light that developer code is the largest part of the application. As a result, there’s less JavaScript to download, parse, and execute, freeing you up for other tasks.

Ember.js

Ember.js is an open-source JavaScript framework for developing large client-side web applications with structured and organized code according to the MVC model. This framework uses route as a model and a handlebar template for views, as well as employs controllers to edit the data in the model.

Responsive Web Development

Here’s a frequently asked question: “What Is responsive web development?” RWD, also known as responsive design, is a web-design approach that emphasizes user experience. The objective is to ensure consistent rendering of webpages on various devices, screens and windows of different shapes and sizes, etc. Such an approach has become important given the rise of mobile devices, with most web traffic coming from mobile-device users. Real-world implementations of RWD abound, which most users, who focus on only the convenience and appeal of websites, rarely notice.

Following are several techniques with which to make websites responsive to various conditions:

  • Flexible grids. Grids are a standard design tool for building websites. Responsive websites require a flexible grid that can load in different ways, depending on the screen or window size.
  • Breakpoints. Similar to flexible grids, breakpoints are dots on a page that identify cut-off points so that information can move on the screen. Most websites have numerous breakpoints, but a minimum should be three to correspond to the three most common device types.
  • Prioritization. Effective designs usually place the most important images and information higher up on the webpage, ensuring that visitors see them first. This visual hierarchy is especially crucial for responsive websites because smaller screens display less of a page at a given time. Prioritizing the important elements keeps mobile-device users engaged.
  • Flexible images. Images are often harder to fit into different screen sizes than plain text. Web designers use various techniques to ensure that web pages display images appropriately on different screens. For example, the display might crop parts of an image for a better fit. In the case of multiple image versions for a site, select the version to render based on the device type or screen size.
  • Responsive media queries. These are coding commands that set the maximum and minimum dimensions for media assets and that specify their orientation. As a result, all media assets on a webpage load at the appropriate size.
  • Mouse and touchscreen-friendly elements. Desktop users are adept with their mouse device, but some actions are less intuitive on mobile devices. Responsive websites must accommodate smartphones by ensuring that every action is easily accessible through a touchscreen. Links must be large and obvious on small screens, and scrolling must be easy across device types. Be sure to test the user experience to ensure that all the elements work well on different devices.

For more details, see How to Create Images for Responsive Web Design.

Types of Web Applications

Web applications are divided into six types.

Static Web Applications

Based on HTML and CSS, static web applications contain no dynamic elements and are primarily for displaying content and data only, allowing no interactions between users and servers. Hence, these applications, the common ones being portfolio sites and official company sites, are relatively easy and simple to build, modify, and manage. Note that despite being static, these applications can include videos, GIFs, and animated banners.

Dynamic Web Applications

Dynamic web applications offer interactions between the server and user, i.e., the user makes a request, which the server accepts and then generates content in real time. These applications, which often hold databases or forums and which constantly update or modify the content, usually perform updates through a content management system (CMS). You can build these applications with various web languages, but PHP and ASP are the best for structuring content.

E-Commerce Web Applications

E-commerce web applications, which are online stores that promote and sell products or services, typically offer a rich set of features that facilitate purchase transactions. As a rule, these are interactive applications through which users can interact with the server and which you can integrate with other systems to better manage interactions and inventory.

For more details, see Select the Right E-commerce Platform for Your Needs.e-commerce platforms.

Single-Page Applications

Single-page applications (SPAs) display updated content by loading a single document with a JavaScript API, e.g., XMLHttpRequest and Fetch. Consequently, since users need not load new webpages from the server, higher performance and a dynamic user experience follow. However, because SPAs are more complex than other web applications, more effort is required to monitor the performance, maintain the state, and implement navigation capabilities.

Progressive Web Applications

Progressive web applications (PWAs), which are websites that function as mobile applications through mobile-native features, require no software purchases or downloads from app stores by users. To locate and access PWAs on their browser, users can start with a search-engine query.

With PWAs, you can develop mobile-native applications for mobile operating systems. As with YouTube videos, devices progressively download PWA content, delivering a more smooth user experience than that from traditional websites through responsive design.

Ultimately, PWAs offer mobile browsers many benefits of native applications with a goal of blurring the distinction between mobile-web and mobile-native applications.

For more detail, see Progressive Web Apps: Architecture and Examples.

SaaS Applications

Given that the software-as-a-Service (SaaS) delivery model enables hosting of applications, independent software vendors (ISVs) can contract with a cloud provider for that service. Cloud providers can also serve as ISVs.

SaaS applications typically adopt a multitenant approach, running a single application instance on host servers. That instance serves each cloud tenant or customer while the application runs on a single version and configuration slated for all tenants or customers. Thus, multiple customers run on the same cloud instance through a common infrastructure and platform even though their data remains segregated.

As a result of that setup, cloud providers can apply changes for all customers through a single, shared instance, more efficiently performing maintenance tasks, fixing bugs, and delivering updates .

For more details, see The Evolution of SaaS Architecture.

Types of Content in Web Applications

Given the importance of content in the digital economy, many web and mobile applications, such as those in the media and news sector, provide content as an integral part of their functionality. Content is also essential in social media and applications geared for messaging, task management, and sharing of text, imagery, or video among users.

While developing web applications, you must do the following vis-à-vis content:

  • Incorporate mechanisms that enable dynamic serving of content in various formats.
  • Add elements that facilitate moderation, curation, or rating of content to beef up its quality.
  • Optimize the content, especially rich media, for fast and accurate page loads.
  • Display user-generated content (UGC), if any, in a captivating manner and offer users a convenient way in which to share that content.

Adding User Generated Content (UGC) to Applications

Contributed at no charge by users and not generated or purchased by application owners, UGC can make applications much more attractive to users. That’s because it’s authentic and created by fellow site visitors or even by social connections.

Before adding UGC to an application, carefully consider these aspects:

    • Input mechanisms. You must offer users secure input forms or other mechanisms to prevent attacks like code injection and cross-site scripting (XSS). To foster contributions, ensure that those mechanisms are highly intuitive.
  • Storage and data management. UGC images and videos can take up large data volumes. Even textual content at large scale requires a robust database infrastructure. So, plan for the type and scale of content and use techniques like compression, conversion to suitable formats, and application of rate limits.
  • Optimization. Be sure to optimize UGC-originated rich media for a sharp and attractive display with techniques like cropping, resizing, and parameter adjustments. Also, optimize the media file size to ensure high performance.
  • Quality. Introduce features like rating, curation, and voting (whether by users or site editors) to control the quality of UGC. Also critical is a way in which to screen and moderate inappropriate content, which is a major problem in most industries. .

For more details, see the following pages on Cloudinary:

Adding Imagery and Video to Applications

Images and videos have become ubiquitous in both web and mobile applications. When correctly leveraged, visual content enhances user experience and is readily consumed by users.

Before adding to your application a large number of images and videos, which necessitate ongoing management and maintenance, think about how to meet the following requirements:

  • Continual updates. Considerable manual efforts are necessary to adjust all your images and videos to the format, size, and aspect ratio required by the application, especially in the case of a huge volume of media that needs frequent updates. Responsive applications that call for multiple image versions for different screen sizes further aggregate this problem.
  • Video encoding and processing. Before serving videos to users, you must encode them in formats that are supported by the various user devices. A fine balance exists between ensuring adequate video quality and high performance at different connection speeds.
  • Video storage. Video files are large and can quickly overwhelm an organization’s servers. Cloud storage is a good solution because, besides offering large scale, it enables video streaming to users directly from cloud servers, reducing the load on application servers.
  • Video players. To serve video to users, applications must include a video player. A simple way to do that is with the HTML5 video tag. Many players that offer advanced capabilities are available, some open source and some commercial. Be sure to carefully test them with other elements of your application.

For more details, see the following:

In addition, this Cloudinary page describes how the Cloudinary Media API can help you manage, optimize, and deliver rich media.

Adding Marketing Content to Applications

Many organizations create applications to meet marketing goals. For example, a clothing chain would share with its users an application on which to browse new product offers, make purchases, and join loyalty programs.

Here are the key factors to consider vis-à-vis development of applications with marketing content:

  • Conversion elements. Since they are measured by the conversions they generate, marketing-oriented applications must contain features that encourage users to perform actions that help advance the company’s marketing goals.
  • Brand equity. Aimed for sharing a brand’s values, marketing content must be carefully crafted and presented to ensure delivery of the right message.
  • Usability and value. Ultimately, marketing applications must be user friendly, useful, and compelling. Balance that requirement with marketing objectives to boost user engagement.

For more details, see Twelve Types of Marketing Videos and 10 Ways to Make Them Great.

Best Practices for Enhancing Application Performance

Performance, a critical consideration in application design, is becoming increasingly important as a means of winning user satisfaction. Following are best practices for improving application performance.

Reduction of Load Time

Load time is the amount of time it takes for websites to render the related files and download them to a user’s computer. For mobile applications, load time is how long they take to initially load or display new screens or interface elements.

Load time can be affected by latency, file size, and the number of files. Keeping files as small as possible and reducing the number of HTTP requests are common techniques for shortening load times.

Smoothness and Interactivity

Besides loading fast, applications must also be stable and easy to use. That is, they must scroll smoothly; their buttons must respond correctly to clicks; and their dynamic elements must move smoothly and react immediately to user actions.

Improve smoothness by minimizing UI updates during user interactions with your application. For example, using CSS animations instead of JavaScript can minimize UI redraws due to DOM changes. Frameworks like React Native enhance interactivity by dynamically reloading a page to display the various parts of the interface instead of having to reload the page.

Perceived Performance

Even though a key measurement of user experience is an objective analysis of site speed, studies show that awareness of website speed counts more than objective statistics. Perceptions of performance are subjective and difficult to assess, however. As a solution, for operations that take a long time, display to the user a useful hint or an entertaining joke during the operation, or a clear message that points out how long the operation will take. The user can then choose to turn to other tasks or stay engaged.

A smart UX strategy often translates to more satisfied users and lower abandonment of websites or mobile apps—even if certain operations or pages take a while to complete or load.

Performance Measurements

Be sure to measure and continually monitor the actual and perceived speed of your application. That is, optimize your application and monitor its performance on an ongoing basis. Adopting metrics that depict success or failure and the tools to measure them helps optimize performance.

Here are the back-end metrics that offer clues on application-performance issues:

  • Application scale
  • Number of DOM nodes
  • Number of resource requests
  • Request latency
  • JavaScript performance
  • CPU and memory load on servers

Additionally, these end-to-end metrics help quantify the actual user experience:

  • Page load times
  • Core Web Vitals (CWV) metrics
  • Latency for critical operations, such as purchase transactions

Be sure to check out application performance management (APM) solutions that offer more complex end-to-end performance measurements and use synthetic requests to simulate the user experience.

Image and Video Optimization

Oftentimes, images and videos take up most of the data on websites or web applications. Since most users in many industries access applications on mobile phones, file size and performance are important considerations. Even on fast connections, every second in page load counts. Therefore, optimizing images and videos to reduce page weight, load times, and network resource loads is a must-do.

You can optimize images in these three ways:

  • Compress images. Compressing images reduces their file size by lowering the level of detail. Look up the various file formats, some of which offer lossless compression without noticeable quality loss. Lossy compression usually results in higher compression ratios but with visible degradation in image quality.
  • Adopt the vector file format. Vector file formats like SVF encode the structure of images without fully rendering them, greatly reducing the file size. Replacing raster images with vector images accelerates page loads without compromising quality.
  • Cache images. Possibly the most efficient optimization technique, catching images stores them in the user’s browser cache or a proxy server nearby. If your site contains static images that are shared across multiple pages or viewed by multiple users in the same location, caching those images is a wise step to take.

Here are a few ways in which to optimize videos:

    • Switch to progressive video formats. Progressive formats like H.264, VP9, and AV1, which offer high compression efficiency, are widely supported by client devices.
  • Adopt video formats with adaptive bitrates. Formats like HLS and MPEG-DASH can adapt their quality to the bandwidth available to the user, delivering reasonable video quality even over slow connections.
  • Deliver media through content delivery networks (CDNs). With CDNs, you can instantly stream video to users, reducing download and buffering time. Also, since CDNs store video files in physical locations close to users, significantly higher performance results for static video files.

For more details, see the following:

Lazy Loading

Lazy loading means delaying the loading of a resource or object, e.g., displaying a placeholder of an image not yet in the user’s viewport and loading the image when the user scrolls down and reaches it. That way, you not only shorten the initial load time, but also conserve bandwidth and system resources on both the client and the server.

To recap, lazy loading offers three benefits:

  • Reduction of initial load time
  • Conservation of bandwidth
  • Conservation of system resources on both the client and the server

For more details, see Lazy Loading: Choosing the Best Option.

Front-End Security Best Practices

Consider the steps below to secure the front end.

Use HTTPS Only

Web applications served over regular HTTP are vulnerable to man-in-the-middle (MitM) and downgrade attacks. In contrast, HTTPS offers greater security by means of encryption, preventing hackers from snooping data.

Here’s what takes place behind the scenes:

  • The HTTP Strict Transport Security (HSTS) header prevents the browser from loading websites with HTTP.
  • The browser automatically converts all HTTP-based access attempts to HTTPS requests.
  • If a browser redirects the initial HTTP-based connection to HTTPS, it might create an opening for a MitM attack—a risk that’s mitigated by the Strict Transport Security (STS) header.

Accordingly, ensure that browsers can serve your application over HTTPS only.

Note: HTTPS requires valid TLS certificates for encryption. The private key must be adequately secure on the server.

Secure the Browser With CSP

Content Security Policy (CSP), a browser standard that detects and mitigates several types of code-injection attacks, ranging from clickjacking to XSS, is the key to securing front-end applications. By limiting the source domains from which the browser loads external resources, CSP prevents it from executing malicious inline code.

To enable CSP, set the content-security-policy header to a set of directives, delimited by semicolons.

For more details, see Browser Security: Threats, Solutions, and User Education.

Authenticate With OAuth and OIDC

OAuth is a REST API standard for delegated authorization. To secure client access, leverage the OAuth framework, which runs over HTTPS, authorizing APIs, devices, and servers with access tokens instead of credentials.

Thanks to the OAuth operations below, applications can obtain specified access scopes of user data without a password:

  • OAuth decouples authentication and authorization, supporting various device types and use cases, including browser-based, server-to-server, and mobile applications.
  • Clients can verify end-user identities according to the authentication performed by the authorization server through OpenID Connect (OIDC), an identity layer that sits on OAuth. Additionally, you can retrieve the basic information in end-user profiles in a REST-based, interoperable manner.

Given OIDC’s extensible specifications, participants can add features like identity-data encryption, search for OpenID providers, and session management.

For more details, see the following:

Leverage a CDN

Content delivery network (CDNs), a transparent mechanism for delivering web content, shorten physical distances, accelerate rendering, and improve site performance through virtualization by means of reverse proxy technology. CDNs reside in front of back-end servers.

Given their location at the edge of the network perimeter, CDNs act as a virtual security fence by blocking distributed denial-of-service (DoS) attacks, which must be addressed before they reach the core network infrastructure.

For more details, see The Essential CDN Guide.

Automation of Management of Media and UGC in Front-End Development With Cloudinary

Since rich media determines whether your site or application’s user experience is engaging, be sure to automate the process of managing media assets and creating multiple versions for delivery. Don’t let those tasks be a burden on developers and creative professionals.

Cloudinary offers an intuitive user interface, replete with APIs and widgets, with which you can store, transform, optimize, and deliver images, videos, and other rich media. Below are the key capabilities.

  • Hosting of imagery and video: Storage on AWS and Google Cloud with enterprise-class backup, revision history, and disaster-recovery features.
  • Support for all media formats: Images (including 3D ones), videos, GIFs, PDFs, PSDs, AVIFs, and all other types.
  • Machine learning-based algorithms: Metadata tagging, background removal, content-aware cropping, video previews, and other media-management features.
  • Real-time image enhancements: Creation of banners on the fly from the same image along with overlays of logos, text, badges, or watermarks, as desired.
  • Expeditious page loads: Automated serving of images and videos—all optimized for high quality and proper format—in browsers or viewports.
  • Automated and efficient delivery: Delivery at high speeds through single, multiple, or regional CDNs.


To get started, sign up for a free Cloudinary account.

See Additional Guides on Key Front-End Development Topics

CSS Image

Authored by Cloudinary

E-Commerce Platform

Authored by Cloudinary

HTML5 Video Player

Authored by Cloudinary

Lazy Loading

Authored by Cloudinary

Live Streaming Video

Authored by Cloudinary

Marketing Videos

Authored by Cloudinary

Responsive Images

Authored by Cloudinary

User Generated Content

Authored by Cloudinary

Video Format

Authored by Cloudinary

OAuth

Authored by Frontegg

Authentication

Authored by Frontegg

Browser Security

Authored by Hysolate

SaaS

Authored by Frontegg

CDN

Authored by Imperva