,

Adding custom code to your website

Sometimes it’s required to add custom code that extends the functionality of your website. In WordPress, you have two ways that are recommended.

Theme’s functions.php

A file called functions.php should be placed in the root of your themes folder at wp-content/themes/yourtheme/functions.php. If this file doesn’t exist create a new one and place all your custom code in this file.

Your custom code will only get executed if this theme is active. If you switch to a different theme all the code in your functions.php file will stay unused.

Dedicate Plugin

If you like to use custom code across multiple themes you should create a dedicated plugin. While creating a plugin for WordPress is a bit more complex it will bring the advantage of disabling it explicitly via your backend.

Please check the official guide on how to create a plugin.

There no difference in performance if you put your code in the functions.php or in a plugin.

Please find more info about customization in the WordPress environment on the official website.