515 Front-end developer tools

Explore how browser-based tools support debugging, performance testing, and accessibility checks in front-end development.

Overview

In this topic, we explore how front-end developers use browser developer tools to inspect, test, and refine their code. These tools—commonly built into web browsers like Chrome, Firefox and Edge—allow developers to examine HTML, CSS, and JavaScript as they run in the browser. Students learn how to debug code, analyse network activity, and test the appearance and behaviour of a webpage across different devices.

Targets

In this topic, students learn to:

• Open and navigate browser developer tools

• Inspect and modify HTML and CSS in real time

• Use the console to run JavaScript commands and check for errors

• Analyse page load performance and network activity

• Test layout and responsiveness using device emulators

• Evaluate accessibility features and simulate user constraints

Syllabus references

Programming for the web

Designing web applications

• Explore and explain the influence of a web browser on web development, including the use of developer (dev) tools

Key features of developer tools

Elements panel

The Elements panel shows the HTML structure of the current page, including any dynamic changes made by JavaScript. Developers can:

• View and edit HTML directly

• Inspect styles applied to specific elements

• See the box model, margins, padding and computed values

This is useful for debugging layout issues and testing design changes on the fly.

Styles and CSS tools

CSS rules can be enabled, disabled, or overridden in real time. The browser highlights which rules are active and how specificity affects style application.

Console

The JavaScript console allows developers to:

• Log errors and warnings

• Run commands manually

• Track the flow of scripts or application state

Console logs are a primary tool for debugging front-end logic.

Developer tools allow live inspection of HTML, CSS and JavaScript while a page is running in the browser. This supports rapid debugging and testing.

Network tab

The Network tab shows the requests and responses made by the browser when loading a page. Students can observe:

• How many files are loaded

• Which resources take longest to load

• What status codes (e.g. 200, 404) are returned

This is helpful for evaluating performance and diagnosing missing assets.

Device emulator and accessibility tools

Developer tools allow simulation of different screen sizes, orientations, and input modes. Many browsers include:

• A mobile view with adjustable screen sizes

• A colour blindness simulator

• Screen reader support and accessibility tree inspection

Testing accessibility early in the development process ensures inclusive design.

Summary

Browser developer tools are essential for modern front-end development. They provide live feedback on how HTML, CSS, and JavaScript behave in real environments. By inspecting elements, debugging scripts, simulating devices and checking accessibility, students can develop higher quality, more inclusive web applications.