Browser developer tools are the basic tools for front-end development, used to debug web pages, optimize performance and view page structure. The opening method includes shortcut keys (F12 or Ctrl Shift I / Cmd Option I), and right-click menu to select "Check". The main functions are: 1. Elements are used to view and edit HTML and CSS in real time, and debug style problems; 2. Console is used to output debugging information, execute JS commands and view errors; 3. Network panel is used to monitor request details, load resources and disable cache simulation first loading; 4. Performance is used to record and analyze page loading metrics, JS execution and rendering bottlenecks; in addition, local storage viewing, device simulation, source code debugging and color picking functions, which are not commonly used but are crucial in specific scenarios.

Browser Developer Tools is a set of practical tools built into modern browsers to help developers debug web pages, optimize performance and view page structure. They are not some mysterious black technology, but basic tools that every front-end developer uses in daily life.

How to open the developer tools

In most mainstream browsers (such as Chrome, Firefox, Edge), the opening method is basically the same:

• Shortcut keys : Press F12 or Ctrl Shift I (Windows/Linux), Cmd Option I on Mac
• Right-click menu : Right-click any element of the web page → select "Inspect"

After opening it, you will see a panel, which usually displays the "Element Inspector", which is the real-time editing interface for HTML and CSS.

What are the main functions

1. Elements

This is one of the most commonly used panels. you can:

• View the HTML structure of the current page
• Modify HTML and CSS in real time, and see the effect changes instantly
• Debug style issues, such as why a button is not centered

Tips: Click the small arrow icon in the upper left corner (or press Ctrl Shift C ) to automatically highlight the corresponding HTML code by hovering the page elements.

2. Console

This is the output location of JavaScript's run log, and it is also the place where you execute temporary scripts.

• Print debugging information ( console.log() )
• Directly enter JS command to test logic
• Check the error message and quickly locate JS errors

Common phenomena: Some functions of the page are invalid, but you can't see any prompts. At this time, you have to go to Console to see if there is any red error message.

3. Network panel (Network)

This panel allows you to see what exactly happened during the loading process of the web page:

• URL, status code, time-consuming for each request
• Request header and response header information
• Loaded resource size (image, JS, CSS)

Suggestion: Check "Disable Cache" when refreshing the page to simulate the first loading situation more realistically.

4. Performance analysis

If you want to know where the page loads slowly, come here:

• Record various indicators during page loading
• Analyze JS execution time and rendering bottlenecks
• Check FPS (frame rate) to determine whether it is stuck

How to use: Open the Performance panel → Click the Record button → Refresh the page → Stop recording → Analyze the chart.

What else can developer tools do

• View local storage : View cookies, localStorage, sessionStorage in the Application panel
• Device simulation : Switch to mobile phone view and test responsive layout
• Source code debugging : Debug JS line by line at the breakpoint of the Sources panel
• Color pickup : Click the color value in CSS to directly call the color board to select the color

These features are not necessarily used every day, but are very critical when troubleshooting specific problems.

Basically that's it. Browser developers seem to have many tools, but in fact, they are commonly used by those panels. After you become proficient, you will find that it is more convenient than any external tool.

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