How to configure a custom error 404 page in azure app service

Question

How to configure a custom error 404 page in azure app service

Neerav Agrawal 50

In configurations -> error pages - I do see the options for 403, 502, 503 error pages only. But not sure how to configure 404 page?

VenkateshDodda-MSFT 24,671 Reputation points Microsoft Employee

2023-07-24T10:13:45.3+00:00

@Neerav Agrawal Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.

Currently custom error pages on Azure App Service is in Preview and as mentioned here you can only implement 503,502 and 403 errors.

If you want to implement custom error for 404 errors, then you need configure it through your application code using web.config file as shown in this sample for your reference.

Feel free to reach back to me if you have any further questions on this.

Neerav Agrawal 50

Thanks @VenkateshDodda-MSFT

I added the web.config file with below code. The code base is node js. But still the 404 is not redirecting.

<configuration>
<system.webServer>
    <httpErrors errorMode="DetailedLocalOnly" defaultPath="/404" defaultResponseMode="ExecuteURL">
    <remove statusCode="404" subStatusCode="-1" />
    <error statusCode="404" prefixLanguageFilePath="" path="/404" responseMode="ExecuteURL" />
    </httpErrors>
</system.webServer>
<system.web>
    <customErrors mode="On">
    <error statusCode="404" redirect="/404" />
    </customErrors>
</system.web>
</configuration>

But still it is showing below :

Neerav Agrawal 50 Reputation points

2023-07-27T17:06:36.9366667+00:00

Any further recommendations to resolve this please ?
VenkateshDodda-MSFT 24,671 Reputation points Microsoft Employee

2023-07-31T04:54:47.85+00:00

Hello @Neerav Agrawal ,

Following up to see if you have a chance to check my previous response and helped. Do let us know if you have any further questions on this.

2 answers

Your answer

VenkateshDodda-MSFT 24,671 Reputation points Microsoft Employee

2023-07-24T10:13:45.3+00:00

@Neerav Agrawal Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.

Currently custom error pages on Azure App Service is in Preview and as mentioned here you can only implement 503,502 and 403 errors.

If you want to implement custom error for 404 errors, then you need configure it through your application code using web.config file as shown in this sample for your reference.

Feel free to reach back to me if you have any further questions on this.
Neerav Agrawal 50 Reputation points

2023-07-24T18:26:09.8366667+00:00

Thanks @VenkateshDodda-MSFT

I added the web.config file with below code. The code base is node js. But still the 404 is not redirecting.

<configuration> <system.webServer> <httpErrors errorMode="DetailedLocalOnly" defaultPath="/404" defaultResponseMode="ExecuteURL"> <remove statusCode="404" subStatusCode="-1" /> <error statusCode="404" prefixLanguageFilePath="" path="/404" responseMode="ExecuteURL" /> </httpErrors> </system.webServer> <system.web> <customErrors mode="On"> <error statusCode="404" redirect="/404" /> </customErrors> </system.web> </configuration>

But still it is showing below :
Neerav Agrawal 50 Reputation points

2023-07-27T17:06:36.9366667+00:00

Any further recommendations to resolve this please ?
VenkateshDodda-MSFT 24,671 Reputation points Microsoft Employee

2023-07-31T04:54:47.85+00:00

Hello @Neerav Agrawal ,

Following up to see if you have a chance to check my previous response and helped. Do let us know if you have any further questions on this.

Answer 1

@Neerav Agrawal apologize for the delay in my response. You might have missed to attach the output what you are getting.
Custom error pages are for errors that terminate on the FrontEnd (ie, request that doesn't make to your app). In this sense a 404-error page is not meaningful, since when a 404 comes from the FrontEnd it means we were unable to find a site for a hostname in the first place!

Once the request gets to the app it is assumed the customer can use whatever error page they want.

I have written the below custom error config in my web.config file and test it as well. All the requests coming to the root url of the webapp it is showing the default page if we request to the path which doesnt exists in my application. it is redirecting the content in 404.html file. As shown below.

<configuration>
    <system.webServer>
        <httpErrors errorMode="Custom" defaultResponseMode="ExecuteURL">
              <remove statusCode="404" subStatusCode="-1" />
              <error statusCode="404" path="/404.html" responseMode="ExecuteURL" />
          </httpErrors>

    </system.webServer>
</configuration>

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Answer 2

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How to configure a custom error 404 page in azure app service

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