Home Assistant 404 Not Found: How to Fix It

If you use Home Assistant, you may have encountered a "404 Not Found" error when trying to access it. This can be frustrating, especially if you rely on Home Assistant for your smart home automation.

In this article, I'll explain some causes of the Home Assistant 404 not found error and provide step-by-step instructions for fixing it.

What does HTTP 404 Not Found Mean?

Before we look at the causes and fixes it can be useful to understand what 404 not found is.

HTTP 404 Not Found is an error message that is returned by a web server when it is unable to locate the requested resource or page.

When you request a web page or resource using your web browser, your browser sends a request to a web server, which then responds with the requested content. However, if the server is unable to find the requested resource or page, it will return an HTTP 404 Not Found error to your browser.

This error message typically means that either the URL you are trying to access is incorrect or that the resource or page you are trying to access has been deleted or moved.

What Causes the Home Assistant 404 Not Found Error?

The Home Assistant 404 not found error occurs when Home Assistant is unable to find the page you're trying to access. This can happen for a few different reasons:

1. Incorrect URL

The most common cause of the 404 error is an incorrect URL. Make sure you're using the correct URL to access Home Assistant. If you're not sure what the URL is, check the documentation or try accessing it from a different device on your network.

2. Corrupt Configuration File

If your configuration file is corrupt, it can cause Home Assistant to return a 404 error. To fix this, you'll need to restore your configuration file from a backup or rebuild it from scratch.

3. Broken Installation

If your Home Assistant installation is broken, it can cause a 404 error. This can happen if you've recently updated Home Assistant or installed a new add-on. To fix this, you'll need to troubleshoot your installation and fix any issues.

Check the Home Assistant blog page for release notes of your version of Home Assistant, it may include breaking changes. This may give you a clue as to what has caused the problem and provide specific instructions on what you need to do to resolve it.

4. Authentication Problems

If you're having authentication problems with Home Assistant, it can cause a 404 error. Make sure you're using the correct username and password to log in.

How to Fix the Home Assistant 404 Error

Now that you know what causes the 404 error, let's look at how to fix it. Follow these steps:

Step 1: Check the URL

Double-check the URL you're using to access Home Assistant. Make sure it's correct and matches the URL in your configuration file.

Step 2: Restart Home Assistant

Sometimes a simple restart can fix the 404 error. Restart Home Assistant and try accessing it again.

To restart Home Assistant go to Settings then System and click the power button from the top right of the screen and select Restart Home Assistant. If you are using Home Assistant OS i'd recommend a full reboot instead, which can be found by clicking advanced settings from the power menu.

Step 3: Check the Configuration File

If the restart didn't work, check your configuration file for errors. Use the YAML validator to check for any syntax errors or typos. If you find any errors, fix them and restart Home Assistant.

To check for YAML errors go to Developer Tools then select the YAML tab. Click the Check Configuration button, if errors are found they will be displayed on the screen. If your configuration is correct it will displayed like in the screenshot below.

Step 4: Restore from Backup

If your configuration file is corrupt, restore it from a backup. If you don't have a backup, you'll need to rebuild the configuration file from scratch.

To restore a backup of Home Assistant go to Settings then System then Backups. Click on a backup from the list then click on the Restore button.

Step 5: Troubleshoot Your Installation

If your Home Assistant installation is broken, you'll need to troubleshoot it. Check the logs for any errors and fix them. If you're not sure how to troubleshoot your installation, refer to the documentation or seek help from the Home Assistant community.

Things to check in your Configuration.yaml file

• Check that frontend: or default_config: has been added to configuration.yaml. Use SMB or SSH to add it back in.

• Issues with custom themes - remove or comment out themes: from your configuration.yaml file

Check your Reverse Proxy configuration

If your Home Assistant server is configured behind a reverse proxy the issue could be caused by an invalid configuration of the proxy.

Try a process of elimination by trying to access your Home Assistant server using the internal URL. This will bypass the reverse proxy and if Home Assistant works then you know the issues lie within your reverse proxy.

Step 6: Reset Your Password

If you're having authentication problems, reset your password. Follow the instructions in the Home Assistant documentation to reset your password.

Final Thoughts

The Home Assistant 404 error can be frustrating, but it's usually easy to fix. By following the steps outlined in this article, you should be able to resolve the issue and get back to using Home Assistant as usual.

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