AutoMapper is dual licensed. To configure the commercial license, either the license key can be set using Microsoft.Extensions.DependencyInjection integration:

services.AddAutoMapper(cfg => {
    cfg.LicenseKey = "License key here";

    // Other configuration
});

Or on non-MS.Ext.DI scenarios, where you’re using AutoMapper directly, you can set the license key in the constructor for the MappingConfiguration:

var mapperConfiguration = new MapperConfiguration(cfg => {
  cfg.LicenseKey = "License Key Here";
}, loggerFactory);

You can obtain a valid license from the AutoMapper website.

Auto-Discovery via Environment Variables

If no license key is set in code, AutoMapper looks for one in environment variables. This is convenient for containerized and cloud environments, and for enterprises that share a single key across many services without code changes:

  • AUTOMAPPER_LICENSE_KEY – the AutoMapper-specific license key.

  • LUCKYPENNY_LICENSE_KEY – a shared key usable across Lucky Penny products (for example, MediatR reads the same variable). Because it is shared, the key must be for a license that includes AutoMapper (a Bundle or AutoMapper edition); a MediatR-only license will not validate here.

The license key is resolved in the following order of precedence, using the first value found:

  1. An explicit value set in code (cfg.LicenseKey = "...").

  2. The AUTOMAPPER_LICENSE_KEY environment variable.

  3. The LUCKYPENNY_LICENSE_KEY environment variable.

No code change is required when using an environment variable—just register AutoMapper as usual without setting LicenseKey.

License Enforcement

Licensing is enforced via log messages at various levels:

  • INFO: Valid license message

  • WARNING: Missing license message

  • ERROR: Invalid/expired license message

There is no other license enforcement besides log messages. No central license server, no outbound HTTP calls, no degrading or disabling of features.

The log messages are logged using standard Microsoft.Extensions.Logging loggers under the category name LuckyPennySoftware.AutoMapper.License.

Multiple License Messages

If you see duplicate license log messages at startup, this is typically caused by AutoMapper being registered or configured more than once in your application.

Using AddAutoMapper (Microsoft.Extensions.DependencyInjection)

Calling AddAutoMapper multiple times in the same IServiceCollection is safe. After the first call registers IMapper, subsequent calls are ignored and no additional license validation occurs:

services.AddAutoMapper(cfg => { cfg.LicenseKey = "key"; });
services.AddAutoMapper(cfg => { /* ignored -- IMapper already registered */ });

If you are calling AddAutoMapper in multiple places (e.g. in modular startup code), each call still only results in a single MapperConfiguration singleton and a single license log message.

Using MapperConfiguration Directly

When creating MapperConfiguration instances manually, each instance performs its own license validation, producing a separate log message:

// Each of these logs a license message – avoid creating multiple instances
var config1 = new MapperConfiguration(cfg => { cfg.LicenseKey = "key"; }, loggerFactory);
var config2 = new MapperConfiguration(cfg => { cfg.LicenseKey = "key"; }, loggerFactory);

To avoid duplicate messages, create and reuse a single MapperConfiguration instance for the lifetime of your application, typically registered as a singleton:

// Create once and reuse
var config = new MapperConfiguration(cfg => { cfg.LicenseKey = "key"; }, loggerFactory);
var mapper = new Mapper(config);

Suppressing Duplicate License Messages

If you intentionally have multiple configurations (for example in integration tests or modular scenarios), you can silence duplicate license log messages by filtering the log category:

builder.Logging.AddFilter("LuckyPennySoftware.AutoMapper.License", LogLevel.None);

Client Redistribution Scenarios

In the case where AutoMapper is used on a client, including:

  • Blazor WASM

  • WPF/MAUI/Desktop apps

  • Redistributed clients

The license key should NOT be set as this would result in secrets transmitted to the client. Instead, omit the license key configuration and mute the license message category name using:

builder.Logging.AddFilter("LuckyPennySoftware.AutoMapper.License", LogLevel.None);

This will depend on your logging setup. A missing/invalid license key does not affect runtime behavior in any way.