What method can be used to create a custom field on a product page?

Creating a custom field on a product page can effectively be accomplished by utilizing metafields or Liquid code. Metafields allow you to store additional information for products, collections, and other resources. They provide a structured way to associate extra data attributes with your products, which can be displayed on the frontend using Liquid, Shopify's templating language. This integration enables developers to inject custom data fields that can be styled and positioned according to the design of the theme.

In contrast, directly editing the HTML file on the server is not the recommended approach within Shopify's architecture, as it may compromise the system's integrity and is not supported by Shopify's hosted environment. Similarly, using JavaScript to manipulate product details may allow for client-side adjustments after the page has loaded, but it does not provide a reliable way to create and manage custom data that persists across sessions or is integrated with Shopify's backend. Lastly, relying solely on third-party applications could lead to unnecessary complexity and dependencies when the built-in functionality of metafields and Liquid can achieve the desired customization directly within the theme.