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Dev 101: How to load unpacked extension

ExtensionNinja | 9/12/2022

Chrome browser extension development journey starts by learning how to load your extension without first publishing it to Chrome Web Store. Luckily, it’s very easy to begin and anyone can do it without paying any developer license fees. You just need to do a couple easy steps.

Enabling Chrome extension developer mode

Follow these steps to enable extension developer mode:

  • Enter chrome://extensions/ to your browser address bar
  • Flip Developer mode toggle
  • Now you will see Load unpacked action enabled

Loading your unpacked extension

With developer mode enabled you can finally load your extension. Press Load unpacked and you will be prompted with a file picker. Choose the folder where your manifest.json file is located and an extension will be added to your browser.

Pro tip: You can also load extensions packaged as zip archives. This is useful if you want to share your inprogress extension with friends or colleagues.

You can start with our boilerplate TypeScript extension code.

Problems you may run into when loading your extension

The most common reasons why loading an unpacked extension can fail is due to a malformed manifest.json file or an exception in JavaScript code that runs at install time.

Fixing a malformed manifest.json file is usually easy because error messages are quite descriptive. Errors point to the offending line and you can also use them to search for resolution online.

Figuring out exceptions at JavaScript evaluation time is more difficult. There is usually no meaningful error message. Luckily, no meaningful error message is also indication that you have this type of an issue. You can try to review code for mistakes in JavaScript IDE. Or comment code out until your extension loads again.

Unpacked extensions can be a security threat

Be very careful with sample extensions that you find on the internet. Do not load extensions with code that you do not understand. Hackers can insert code that will steal your social media accounts or will try to trick you into downloading and installing malware on your computer. Unpacked extensions are not reviewed by Google and can use any permission available in the browser platform.

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