Some time we needs to get customer id without session in magento 2. I am going to explain some simple steps to get customer id without session.

Before we start I assume, you have already a created custom module. If you don't have it or don't know how to create it then check out our other article How To Create a Magento 2 Module.

<?php

namespace Vendor\Module\Helper;

class Data extends \Magento\Framework\App\Helper\AbstractHelper
{
   /**
     * @var \Magento\Framework\App\Helper\Context
   */

   protected $userContext;

   public function __construct(
    \Magento\Framework\App\Helper\Context $context,
    \Magento\Authorization\Model\UserContextInterface $userContext
  )
  {
    $this->userContext = $userContext;
    parent::__construct($context);
  }

  public function getCustomerId()
  {
    return $this->userContext->getUserId();
  }
}

Thant's It!
I hope this Magento article helped you to find what you were looking for.