A theme editor is a basic text editor window that allows you to modify all of your theme files in one place. This is an alternative to opening each theme file separately when you want to make changes.
If you’re logged into the administrator area on your website, you can click “Appearance” on the left-hand column and then “Editor” to open the theme editor.
Note: Not every theme comes with the theme editor functionality activated. If you don’t have a theme editor and want one, there are plugins available, or you can choose a theme that has the theme editor function activated.
When you open the theme editor, you’ll see a simple text box showing the content of one of your theme files. On the right-hand side, you’ll see a list of theme files that you can edit. Simply click on the relevant file in order to bring it up in the text editor window.
Keep in mind that your theme files may also include files relating to inactive themes. If you click on one of these inactive template files, you can modify it, but it will not activate the theme itself. To do that, you’ll need to click on “Appearance” and then “Themes.”
Because the theme editor allows you to make changes to the core functionality of your website, it is extremely important to not attempt to modify these files unless you are 100% sure about what you are doing. If you find some code on the internet and paste it incorrectly into one of your theme files, you may break your website or lock yourself out of your own website!
Note: If you’re a theme developer, be aware that the theme editor is turned on by default. You can disable it by modifying the “wp-config.php” file.