Users often receive the error message “iisnode encountered an error when processing the request” while accessing Node.js sites.

As a part of our Server Management Services, our Engineers help to fix similar IIS-related errors regularly.

Today, let us discuss the possible reasons and fixes for this error.

What is “iisnode encountered an error when processing the request” error

The IIS node error generally triggers while accessing a Node.js site. A typical error message includes an internal server error with the following format.

This typically happens when the application pool doesn’t have enough permissions to write to the current folder.

How to fix “iisnode encountered an error when processing the request” error

One of the possible steps that our Support Engineers follow to fix this error is to give the IIS_IUSRS full permission.

This can be performed with the series of steps below:

1. Go to your windows folder application ad right click on properties.
2. From the Security section, click on Edit and then click on Add.
   
3. Now, from the Advanced, use the Find Now and then select the IIS_IUSRS option.
4. Then, Allow the following option: Full control
5. Finally, Restart the application on IIS

Sometimes, users don’t prefer to give the entire IIS_IUSRS group full control. A possible solution in such cases is to get into the advanced settings menu and under Process Model. Then, from identity change the user account to a user that already has write permissions.

Another possible reason for this error could be the use of an older version of windows. Our Support Engineers have noticed a similar error on a system with windows server 2008 R2. An upgrade to a recent windows version fixed the issue here.

Conclusion

In short, this iisnode error triggers when the application pool doesn’t have enough permissions to write to the current folder. Today, we saw how our Support Engineers fix this error.