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Best Chrome Extensions to Inject JavaScript into Webpages

Dinesh Thakur
March 3, 2025
2MIN READ
Discover the best Chrome extensions to inject JavaScript into webpages for debugging, automation, and testing—featuring Requestly, Page Manipulator, and more

Since Chrome’s Manifest V3 (MV3) migration, many older extensions that allowed script injection are no longer available or have limited functionality. This has made it harder for developers, testers, and power users to find reliable tools to inject JavaScript into webpages.

To help you navigate these changes, we’ve compiled an updated list of the best Chrome extensions that still support script injection. Whether you need to debug websites, modify page content, automate tasks, or test APIs, these extensions will make the process seamless and efficient.

Let’s explore the top Chrome extensions for inserting custom scripts into webpages.

Why Insert Custom Scripts into a Webpage?

There are several reasons why developers, testers, and even regular users might need to inject custom scripts into a webpage:

  • Debugging & Testing – Experiment with JavaScript changes without modifying the actual codebase.
  • UI Customization – Modify website elements, hide unwanted sections, or apply custom styles.
  • Automating Tasks – Speed up repetitive actions like form filling, button clicks, or scrolling.
  • API Testing & Response Manipulation – Modify API responses and test different scenarios.
  • Enhancing Web Functionality – Add shortcuts, improve accessibility, or integrate third-party tools.
  • Security Testing – Identify vulnerabilities by testing for script injection and XSS attacks.

Now, Let’s dive into the best Chrome extensions for injecting JavaScript into webpages!

Requestly

Requestly is an all-in-one tool for developers that not only supports JavaScript and CSS injection but also provides powerful features like API response modification, network request interception, and cloud sync.

Requestly Insert Script
Key Features
  • Insert JavaScript and CSS based on URL rules.
  • Modify API responses, redirect URLs, and mock network requests.
  • Cloud sync to store and reuse scripts across devices.
  • Advanced rule-based script execution for testing and debugging.

Page Manipulator

Page Manipulator is a powerful extension that lets you inject JavaScript and CSS into any webpage. It allows scripts to execute automatically based on predefined rules.

Key Features
  • Inject JavaScript and CSS into any webpage.
  • Save and apply scripts automatically on page load.
  • Supports regex-based URL matching for rule-based script injection.
  • Simple UI to add and manage multiple scripts.

User JavaScript and CSS

A simple and straightforward JavaScript injector designed for quick script execution. It features a built-in code editor and allows users to save and reuse scripts easily.

User JavaScript and CSS
Key Features
  • Quickly inject and execute JavaScript on any webpage.
  • Minimalist interface with a built-in code editor.
  • Supports custom script storage for reuse.
  • Lightweight and easy to use.

Moonly JavaScript Injector

A lightweight and easy-to-use extension that allows users to inject JavaScript and CSS into specific webpages. It’s perfect for making quick changes without complex configurations.

Key Features
  • Allows injecting both JavaScript and CSS into any webpage.
  • Simple and lightweight, with a clean UI.
  • Scripts are applied automatically on page load.
  • Supports different scripts for different pages.

Conclusion

If you’re looking for the best Chrome extension to insert scripts into webpages, Requestly is the top choice. It not only allows seamless JavaScript and CSS injection but also offers advanced features like rule-based execution, API response modification, and cloud sync, making it ideal for developers and testers. Try it out and streamline your workflow today!

Written by
Dinesh Thakur
Dinesh Thakur, fascinated by technology since childhood, has mastered programming through dedication. Whether working solo or in a team, he thrives on challenges, crafting innovative solutions.

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