This article explains the auth0Client parameter found in Authentication API endpoint requests and describes how to decode or disable this telemetry information

• auth0Client Parameter 
• Authentication API endpoints

The auth0client parameter contains the telemetry information sent by the Auth0 SDK.

It can be decoded with base64 to reveal the information it carries.

Sample value:  eyJuYW1lIjoiYXV0aDAuanMiLCJ2ZXJzaW9uIjoiOS4xMy40In0
Base 64 decoded: {"name":"auth0.js","version":"9.13.4"}

When supported by the SDK in use, this data can be omitted.
For example, during initialization of the Auth0.js SDK, the telemetry data can be disabled by setting _sendTelemetry to false, as shown in the sample code below:

var webAuth = new auth0.WebAuth({
domain: AUTH0_DOMAIN,
clientID: AUTH0_CLIENT_ID,
_sendTelemetry:false,
// other parameters
});