The EPP code, also known as an authorization or Auth code, is a secret and unique set of characters assigned by the domain registrar.
This code is a safeguard that, along with other security measures such as domain unlocking, guarantees that only the rightful owner can transfer a domain. If a wrong EPP code is provided when setting up a domain transfer, the transfer will not proceed.
The EPP key is required when transferring most domain name TLDs, such as .com, .net, .org, .biz, .info, .us, etc. At Hostinger, you can consult your EPP code from the Domains section of your panel following these steps: How to obtain EPP or Auth code for domain transfer at Hostinger?
There are some exceptions, such as .co.uk or .eu domains, which use a different code. Similarly, certain registrars require the EPP code to be unavailable through the user interface and need to be requested.