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How to Fix Azure Can’t Start Web App Errors? Troubleshooting Guide

rizwanrkiff
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You just deployed your app. Everything looked good… until you tried to open it.

Nothing loads. Maybe you get a 503. Perhaps it just hangs. No clear error, no helpful message. Just you, staring at a screen that won’t move.

If your Azure Web App won’t start, don’t panic. Most of the time, it’s fixable—and easier than you think. We’re going to walk you through the actual reasons this happens, provide fast fixes that work right away.

Common Causes of Azure Web App Startup Failures

Before diving into logs and advanced tools, it’s helpful to understand what typically goes wrong. Here’s what commonly causes Azure App Service to fail at startup:

Knowing these upfront makes every step below faster and more focused.

Quick Fixes for Unresponsive Azure Web Apps

These are simple, immediate actions that often get your app running without deeper digging:

If the issue persists, continue. Now we’ll get specific.

Step-by-Step Azure Web App Troubleshooting Guide

Let’s troubleshoot the right way. We’ll start with the easiest checks, then go deeper until we hit the root of the problem.

1. Start with the Azure Portal

Go to your App Service inside the Azure Portal. Look at the Overview tab. What’s the app status?

If it says Stopped, try clicking Start. If it stays stuck in ‘Starting’ or crashes back to ‘Stopped’, click on ‘Diagnose and Solve Problems’.

That tool does a quick scan of your app’s health, memory usage, config issues, and recent errors. It’s fast and often flags issues you wouldn’t spot on your own.

Check if there are any resource alerts or if the system detected a crash loop.

2. Check the Log Stream

This is where most answers come from.

The Log Stream shows what your app is doing while it starts up. To view it, go to Monitoring > Log Stream, and restart the app.

If nothing appears:

Once logging is active, go back to Log Stream and try again.

Look for signs like:

Those first 10–15 log lines usually point to the root issue. Copy any stack traces—they’ll help you solve or search for more info.

3. Use the Kudu Console

If logs didn’t tell you enough, open the Kudu Console. It gives you direct access to your app’s file system and process list.

Visit:

https://<yourappname>.scm.azurewebsites.net

Click Debug Console > CMD. From here:

If your process isn’t even listed, it likely failed during very early startup—before logs could catch it. That usually means a bad configuration, a broken import, or a missing environment variable.

Resolving Common Azure Web App Errors

These are the most common error types people hit. Each one means something specific—and gives you a clue where to fix.

1. HTTP 500 – Internal Server Error

This means Azure launched your app, but something within the app broke.

Usually it’s one of three things: a crash in your startup code, a missing dependency, or a broken route handler.

Check the Log Stream for exceptions. If you see an error stack trace pointing at a null value, invalid operation, or config binding failure, that’s your culprit.

Fix the crash in your code, deploy again, and restart the app. Also confirm you’re using the correct runtime version in Azure (under General Settings > Stack).

2. HTTP 502 or 503 – Bad Gateway or Service Unavailable

This error occurs when Azure attempts to reach your app but receives no response.

It means your app didn’t bind to a port, crashed before opening a listener, or used up memory too fast.

To fix:

If you’re using Node, confirm you’re listening on the correct port (process.env.PORT). In .NET, confirm your Program.cs doesn’t error out on missing configs.

3. No Status Code — Just “Starting” Forever

This is the silent failure that confuses most users: no code, no response, just a stuck app.

It usually means Azure failed even to launch your process. Something crashed before logs or monitoring could capture it.

Use Kudu to:

In some cases, your deployment didn’t complete, and Azure is starting from scratch. Try redeploying cleanly. If that doesn’t work, roll back to a working version.

When to Contact Microsoft Support for Azure Web App Issues?

There’s a point where you’ve done everything right — but the app still won’t run. That’s when Microsoft Support should step in.

You should contact them if:

Your app won’t start, logs don’t appear, and even the Kudu Console doesn’t load properly. If you’ve scaled, restarted, and redeployed, but nothing works, you may be hitting a quota or platform-level issue that only backend support can resolve.

Ensure you gather the app name, region, resource group, and UTC times of your last few deployments. That helps the support team locate logs and isolate the issue more quickly.

Don’t wait too long if the platform seems unresponsive. Azure Support has access to logs and system-level data you can’t see — and they’re usually helpful once they know what’s failing.

Preventing Future Azure Web App Startup Problems

You can avoid most startup issues with a few simple habits. These steps reduce risk and give you early warnings if something breaks:

Making these part of your process saves time and prevents crashes in future deploys.

Conclusion

When your Azure Web App won’t start, it’s easy to feel stuck. However, the truth is that the problem almost always leaves a clue — in logs, settings, or deployment files.

By following the steps above, you can figure out why it broke, fix it with confidence, and get back to building. Azure provides you with the tools — you just need to know where to find them.

And if nothing works, remember that support is there for a reason. Don’t hesitate to reach out when the platform itself becomes the blocker.

Now that you know what to do, you’re no longer stuck. You’ve got this.

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