Read the article to know more about the troubleshooting steps of “Maximum request length exceeded” error in IIS. Bobcares, as a part of our Server Management Service offers solutions to every IIS query that comes our way.

Overview

1. Fixing “Maximum request length exceeded” error
2. Error Impacts
3. Causes & Fixes for the Error
4. How to Prevent the Error?
5. Conclusion

Fixing “Maximum request length exceeded” error in IIS

When an incoming request’s size surpasses the server’s configured restrictions, web applications hosted on IIS throw the “Maximum request length exceeded” error. This issue often occurs while uploading files or delivering big data sets in one request. The error appears as follows:

This shows that the server has rejected the request due to its size exceeding predefined limits, which can be set both at the application level (in web.config) and at the server level (in IIS settings).

Error Impacts

• User Experience: When users try to upload files that are larger than permitted, they will be prompted with an error notice, which could cause them to become frustrated and have a bad time.

• Program Functionality: The performance of the program as a whole may suffer if crucial features that depend on file uploads or massive data submissions malfunction.

• Data Loss: Users who try to upload data may lose it if they are not aware of size restrictions.

Causes & Fixes for the Error

1. Default Request Limits: ASP.NET limits requests to 4 MB by default via the maxRequestLength setting in the web.config file.

Fix: Update web.config:

<system.web>
<httpRuntime maxRequestLength="20480" /> <!-- Set to 20 MB -->
</system.web>

2. IIS Request Filtering Limits: IIS defaults maxAllowedContentLength to 30 MB.

Fix: Update web.config:

 <system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="31457280" /> <!-- Set to 30 MB -->
</requestFiltering>
</security>
</system.webServer>

3. Incorrect Configuration File: Changes may not apply if made in the wrong web.config.

Fix: Ensure modifications are in the root directory’s web.config or the correct file.

4. Application Pool Settings: IIS application pool settings may conflict with request limits.

Fix: Adjust application pool settings in IIS Manager to match the needs (e.g., Idle Timeout, Regular Time Interval).

5. Client-Side Limitations: Client-side libraries might have size limits.

Fix: Configure client-side controls or libraries to align with server limits. Check library documentation for guidance.

How to Prevent the Error?

• Monitoring and Alerts: To track when this issue happens and make proactive modifications, implement logging and monitoring tools.

• User Guidance: To avoid confusion, also, provide explicit advice on file size restrictions inside the user interface.

• Testing Configurations: To make sure that restrictions are set correctly, we must test configurations on a regular basis following upgrades or deployments.

• Update the documentation: We must make sure the material is current with reference to system configurations.

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Conclusion

The “Maximum request length exceeded” error in IIS occurs when an incoming request exceeds the server’s configured size limits, often during file uploads or large data submissions. To fix this, adjust the ASP.NET and IIS settings in the web.config file and ensure the correct application pool settings. Also, review client-side controls for file size limitations. Proper monitoring, user guidance, and regular testing can help prevent this error in the future, ensuring smooth application performance and user experience.