For authentication on Blynk platform, every device should have a unique AuthToken. AuthToken is the main identifier of every device in the Blynk Cloud. Depending on the hardware, connectivity, and the IoT use-case you are working on, a way of getting AuthTokens for your device can be different.
There are three ways to activate devices on Blynk platform:
Manually create a device using Blynk.Console for initial prototyping (works for any hardware)
For supported devices that can connect to the Internet over WiFi, you can use WiFi provisioning method which is built-in into Blynk.Apps.
Using this method, Blynk.Apps, and Blynk.Edgent will take care of telling your devices how to connect to your home or office WiFi network. New AuthToken will be automatically generated and stored on the device. There is no need to specify WiFi credentials and Auth Token in the firmware code.
Using provided WiFi provisioning is highly recommended if you are working on a commercial WiFi product
This method is especially beneficial for commercial applications because:
You don't know upfront to which WiFi network your clients will connect your devices to
It simplifies the manufacturing process at scale as you use same code without a need to manually add AuthToken to each device
Here is a tutorial on how to activate devices with Blynk.Inject: