Setting License Key in Web.config

Updated:June 1, 2025

This problem has been solved since IronPDF version 2024.3.3.

Exception: Unhandled exception. IronSoftware.Exceptions.LicensingException: IronPDF must be licensed for development.

For older IronPdf versions, specifically those between versions 2023.4.4 and 2024.3.3, there is a known licensing issue in:

ASP.NET projects
.NET Framework version >= 4.6.2

The key stored in a Web.config file will NOT be picked up and used by the product.

Workaround

To address this issue, it is recommended to retrieve the license key from the Web.config file using ConfigurationManager in the code, and then apply it to the License.LicenseKey property.

Example:

<configuration>
  ...
  <appSettings>
    <add key="IronPdf.LicenseKey" value="IRONPDF-MYLICENSE-KEY-1EF01"/>
  </appSettings>
  ...
</configuration>

<configuration>
  ...
  <appSettings>
    <add key="IronPdf.LicenseKey" value="IRONPDF-MYLICENSE-KEY-1EF01"/>
  </appSettings>
  ...
</configuration>

XML

With the XML file provided above, we can use ConfigurationManager to retrieve the license key value and pass it to the IronPdf.License.LicenseKey property.

using System.Configuration;

class Program
{
    static void Main()
    {
        // Retrieve the license key from the Web.config file
        string licenseKey = ConfigurationManager.AppSettings["IronPdf.LicenseKey"];

        // Apply the license key to the IronPdf library
        IronPdf.License.LicenseKey = licenseKey;

        // Additional processing can continue here
    }
}

using System.Configuration;

class Program
{
    static void Main()
    {
        // Retrieve the license key from the Web.config file
        string licenseKey = ConfigurationManager.AppSettings["IronPdf.LicenseKey"];

        // Apply the license key to the IronPdf library
        IronPdf.License.LicenseKey = licenseKey;

        // Additional processing can continue here
    }
}

Imports System.Configuration

Friend Class Program
	Shared Sub Main()
		' Retrieve the license key from the Web.config file
		Dim licenseKey As String = ConfigurationManager.AppSettings("IronPdf.LicenseKey")

		' Apply the license key to the IronPdf library
		IronPdf.License.LicenseKey = licenseKey

		' Additional processing can continue here
	End Sub
End Class

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Curtis Chau

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Technical Writer

Curtis Chau holds a Bachelor’s degree in Computer Science (Carleton University) and specializes in front-end development with expertise in Node.js, TypeScript, JavaScript, and React. Passionate about crafting intuitive and aesthetically pleasing user interfaces, Curtis enjoys working with modern frameworks and creating well-structured, visually appealing manuals.

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