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Fixing Unchecked RuntimeLastError Error in Chrome: Tips and Solutions

Unchecked Runtime.LastError: What It Is and How to Fix It

Are you experiencing a common Chrome error that says, “Unchecked runtime.lastError: The message port closed before a response was received”? This error can be quite frustrating, especially if you don’t know what it means or how to fix it.

Fortunately, we’ve got you covered. In this article, we’ll explain what causes this error and offer some solutions to help you resolve it.

Possible Causes

There are several possible causes of the “Unchecked runtime.lastError” error, but some of the most common ones include:

– Extensions: Often, this error is caused by a faulty or incompatible extension that you have installed on Chrome. – Async Code: This error can also occur when asynchronous code that relies on promises or event listeners executes improperly.

– Incognito Mode: Sometimes, this error may appear only when you’re using Chrome in Incognito mode.

How to Identify the Causing Extension

If you have determined that the error is being caused by a problematic extension, you can use the following steps to identify the culprit:

1. Open the Console tab: Press Ctrl + Shift + I (Windows/Linux) or Cmd + Option + I (Mac) to open the Developer Tools panel.

Then, click on the Console tab. 2.

Toggle errors: If the error message is not already displayed in the console, you should toggle the “Errors” filter by clicking on the filter icon (a funnel) and selecting “Errors.”

3. Refresh the page: Now, refresh the page that gave you the error message.

Any errors or warnings displayed in red text will show you which extensions are causing the issue.

Enabling Specific Extensions in Incognito Mode

If you have found out that the error only occurs in Incognito mode, it’s possible that Chrome has disabled all extensions in this mode. However, you can enable specific extensions to work in Incognito mode using the following steps:


Click on the three dots: Open Chrome and click on the three vertical dots on the top-right corner of the window. 2.

Manage extensions: Choose More Tools > Extensions. This will open a new tab in your browser.

3. Allow in Incognito mode: Find the extension you want to enable in Incognito mode and click on “Details.” Under the extension’s description, you will see a toggle button labeled “Allow in Incognito.” Click on this to toggle it on.

Solutions for Extensions Developers

If you’re an extensions developer and notice that your extension is causing this error, there are a few solutions you can try to fix it:

1. Incorrect Use of runtime.sendMessage():

If you’re using the runtime.sendMessage() method incorrectly, you may encounter the “Unchecked runtime.lastError” error.

This happens when the sendResponse function is not called, or you don’t register an event listener to receive the asynchronous response. To fix this error, you can create a Promise to handle the response asynchronously instead of relying on event listeners.

Here’s an example code snippet that demonstrates how to do this:

chrome.runtime.sendMessage({msg: “hello”}, (resp) => {



function sendMessage(msg) {

return new Promise((resolve) => {

chrome.runtime.sendMessage(msg, resolve);



(async () => {

const resp = await sendMessage({msg: “hello”});



2. Example of Returning True from the Background Event Listener:

If you’re an extensions developer and frequently use the background event listener, remember to always return true once your async/await operations complete.

If you don’t, you may encounter the “Unchecked runtime.lastError” error. Here’s an example of how to use the background listener properly:

chrome.runtime.onMessage.addListener(async (req, sender, sendResponse) => {

if (req.msg === “hello”) {

const response = await Promise.resolve({res: “world”});


return true;



By adding “return true” at the end of the event listener, you’re letting Chrome know that you’re done with whatever asynchronous operation you’re performing and that it can now safely handle your response.


In conclusion, the “Unchecked runtime.lastError: The message port closed before a response was received” error can be quite frustrating, but it’s usually not too difficult to diagnose and fix. If you’re experiencing this error, follow the tips we’ve provided above to identify the culprit and resolve the issue.

If you’re an extensions developer, pay careful attention to how you’re using the runtime.sendMessage() and background event listener methods to avoid encountering this error in the future. Additional Resources: Where to Learn More About the “Unchecked runtime.lastError” Error

If you’re still struggling with the “Unchecked runtime.lastError” error, don’t worry – there are plenty of resources available to help you learn more.

In this section, we’ll provide some suggestions for related topics and tutorials that you can check out to expand your knowledge and hopefully resolve this error for good.

Learn More About Chrome Development

If you’re an extensions developer or just interested in learning more about Chrome development, there are several resources available that can help you deepen your understanding and skills. Here are a few to get you started:


Chrome Developer Documentation: The Chrome DevTools documentation is an excellent resource for learning more about how to develop extensions for Chrome. You can find information on everything from getting started with the basics to debugging more advanced issues.

2. Chrome Extension Examples: It can be helpful to learn by example, and the Chrome Extension Examples repository on GitHub is a great place to find working code snippets and projects that you can use as a starting point for your own extension development.

3. Udemy Chrome Extension Course: If you prefer a structured course rather than self-guided learning, the “Chrome Extension Development: Build 11 Chrome Extensions” course on Udemy is an excellent option.

The course covers a range of topics, from basics to advanced features, and includes hands-on exercises to help you apply what you’ve learned.

Check Out Related Tutorials

If you’re encountering the “Unchecked runtime.lastError” error in the context of a specific feature or functionality, there may be tutorials available that can help you troubleshoot and resolve the issue. Here are a few related topics and tutorials that you might find helpful:


Content Scripts: Content scripts are one of the most powerful capabilities of Chrome extensions, but they can also be complex to work with. The “Content Script Communication with Background Page” tutorial on the Chrome Developer site provides a step-by-step guide to communicating between content scripts and the background page to avoid common errors like the “Unchecked runtime.lastError” message.

2. Messaging: Messaging is another core feature of Chrome extensions, but it can also be confusing to use correctly.

The “Message Passing” section of the Chrome Developer documentation provides detailed information and examples for using messaging to communicate between various components of your extension. 3.

Storage: If you’re encountering the “Unchecked runtime.lastError” error related to storage operations, the “Chrome Storage API: the basics – Storing options” tutorial on Medium provides a clear introduction to the basics of the Storage API and common pitfalls to avoid.


In conclusion, the “Unchecked runtime.lastError” error can be frustrating, but with the right resources and understanding, you can resolve it and move on with your extension development. Whether you prefer to learn through self-guided exploration of resources like the Chrome Developer documentation or prefer structured courses or tutorials, there are plenty of options available to help you deepen your knowledge and skills.

We hope the resources we’ve suggested above will help you resolve this error and continue building amazing Chrome extensions. In summary, the “Unchecked runtime.lastError: The message port closed before a response was received” error can be caused by various issues, including problematic extensions, async code, and Incognito mode.

To fix the error, you can use the Console tab in Chrome to identify the problem extensions, enable specific extensions in Incognito mode, and use best practices when writing asynchronous code as an extension developer. Additionally, there are various resources available for learning more about Chrome development, troubleshooting specific features, and avoiding common errors like this one.

By following these tips and utilizing available resources, you can resolve the “Unchecked runtime.lastError” error and continue building amazing Chrome extensions.

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