How to disable the block editor (Gutenberg)
WordPress 5.0 includes the new block editor (Gutenberg), which will be the default editor from this time on. If you run into any problems or just don't like the new editor, there are different methods available to disable the block editor.
Learn more about Gutenberg
🔗 Classic Editor (made by WordPress contributors)
add_filter( 'use_block_editor_for_post', '__return_false' );