Fix IIS Express Error 0x80070020 In Visual Studio

Oct 31, 2025 by Andrew McMorgan 50 views

Fixing IIS Express Error 0x80070020 in Visual Studio

Hey guys! Ever run into that super annoying IIS Express error 0x80070020 when you're just trying to get your web app running locally in Visual Studio? Yeah, it's a pain. This error usually pops up when something else is hogging the port that IIS Express is trying to use. Maybe you left Visual Studio open overnight in debug mode, like the user who posted about this issue, and now things are all jammed up. Don't worry; we've all been there! Let's walk through some steps to get you back on track so you can get back to coding without wanting to throw your computer out the window.

Understanding the Error

Before we dive into the fixes, let's quickly break down what this error means. The error code 0x80070020 translates to ERROR_SHARING_VIOLATION. In simple terms, it means that IIS Express can't start because another process is already using the port it needs. This is super common, especially if you've been debugging and something didn't quite shut down properly. It could be another instance of IIS Express, some other web server, or even a completely different application that happens to be using the same port. Identifying the culprit is the first step to resolving this issue, and trust me, it's usually easier than it sounds.

Why Does This Happen?

So, why does this sharing violation happen in the first place? Well, a few common scenarios can cause this. One frequent cause is leaving Visual Studio in debug mode for an extended period. Sometimes, the debugging process doesn't cleanly release the port when you expect it to. Another reason could be that you have multiple instances of Visual Studio running, each trying to launch IIS Express on the same port. Or, you might have other web servers like Apache or Node.js running in the background, unknowingly competing for the same resources. Understanding these potential causes can help you prevent the error from recurring in the future. Think of it as learning from your mistakes—or, in this case, from your computer's mistakes!

Steps to Resolve the Issue

Alright, let's get down to business. Here’s a step-by-step guide to fixing the 0x80070020 error. Follow these, and you'll be back to coding in no time.

1. Identify the Process Using the Port

The first thing you need to do is figure out which process is causing the conflict. Thankfully, there's a simple command-line trick to do this. Open up your Command Prompt or PowerShell as an administrator. Then, type the following command and hit Enter:

netstat -ano | findstr :<your_port_number>

Replace <your_port_number> with the port number your IIS Express is trying to use. You can find this port number in your Visual Studio project settings or in the IIS Express configuration file. Once you run the command, you'll see a list of processes using that port. The last column, labeled PID, is the Process Identifier. This is what we need to find the offending process.

2. Kill the Offending Process

Now that you have the PID, it's time to shut down the process that's causing the problem. There are a couple of ways to do this. The easiest is to use the Task Manager. Open Task Manager (Ctrl+Shift+Esc), go to the "Details" tab, and find the process with the PID you identified. Right-click on it and select "End task." This will forcibly close the process, freeing up the port.

Alternatively, you can use the command line again. Open Command Prompt or PowerShell as an administrator and type:

taskkill /F /PID <your_pid>

Replace <your_pid> with the Process Identifier you found earlier. The /F flag forces the process to terminate. Be careful when using taskkill, though; make sure you're killing the right process! Killing the wrong process could lead to other issues. Once you've killed the process, try restarting your web application in Visual Studio.

3. Restart Visual Studio

Sometimes, Visual Studio itself can get into a weird state. A simple restart can often resolve the issue. Close Visual Studio completely, give it a few seconds, and then reopen it. This can clear out any lingering processes or cached settings that might be causing the conflict. It’s a basic step, but you'd be surprised how often it works.

4. Clean and Rebuild Your Solution

Occasionally, corrupted build files can cause issues with IIS Express. To resolve this, try cleaning and rebuilding your solution in Visual Studio. Go to the "Build" menu and select "Clean Solution." Once the cleaning process is complete, go back to the "Build" menu and select "Rebuild Solution." This ensures that all your project files are fresh and up-to-date. It's like giving your project a fresh start, which can sometimes be all it needs to get back on track.

5. Check Your IIS Express Configuration

Your IIS Express configuration file might be the culprit. This file, usually named applicationhost.config, is located in your project's .vs folder. Sometimes, this file can get corrupted or contain incorrect settings. To fix this, try deleting the .vs folder in your solution directory (make sure Visual Studio is closed first!). When you reopen the solution, Visual Studio will recreate the .vs folder and the applicationhost.config file with default settings. This can resolve any configuration issues that might be causing the error. Just remember that you might need to reconfigure some of your IIS Express settings afterward.

6. Change the Port Number

If all else fails, you can try changing the port number that your application uses. This forces IIS Express to use a different port, avoiding the conflict altogether. To do this, go to your project's properties in Visual Studio. Under the "Web" tab, you'll find the "Project Url" setting. Change the port number in the URL to something different (e.g., from localhost:12345 to localhost:54321). Save the changes and try running your application again. This is a simple workaround that can often get you up and running quickly.

Preventing the Error in the Future

Okay, so you've fixed the error—great! But how do you prevent it from happening again? Here are a few tips to keep in mind:

Always close Visual Studio properly: Don't just leave it running in debug mode indefinitely. When you're done, stop the debugging session and close Visual Studio.
Avoid running multiple instances of Visual Studio: If you need to work on multiple projects, try using separate instances of Visual Studio Code or other editors for the other projects.
Be mindful of other web servers: If you're using other web servers like Apache or Node.js, make sure they're not conflicting with IIS Express by using the same ports.
Regularly clean and rebuild your solution: This helps prevent corrupted build files from causing issues.

By following these tips, you can minimize the chances of encountering the IIS Express error 0x80070020 in the future. Trust me, a little prevention goes a long way!

Conclusion

So, there you have it! Fixing the IIS Express error 0x80070020 can be a bit of a hassle, but with these steps, you should be able to resolve it quickly and get back to coding. Remember to identify the offending process, kill it, and consider restarting Visual Studio or cleaning your solution. And don't forget to take preventive measures to avoid the error in the future. Happy coding, and may your ports always be free!