Default CSS

enable custom CSS if and only if page does not define any styles in <head>

You will need to install an extension such as Tampermonkey, Greasemonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Userscripts to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install a user script manager extension to install this script.

(У мене вже є менеджер скриптів, дайте мені встановити його!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(I already have a user style manager, let me install it!)

// ==UserScript==
// @name         Default CSS
// @version      2023-12-23
// @license      WTFPL
// @description  enable custom CSS if and only if page does not define any styles in <head>
// @author       https://matrix.to/#/@belkka:private.coffee
// @match        *://*/*
// @grant        none
// @namespace https://greasyfork.org/users/922438
// ==/UserScript==

// Note: this userscript uses CSS from https://github.com/susam/spcss/ project. Since you are already reading this,
// feel free to replace "https://unpkg.com/spcss" with style sheet of your choice
// or even use <style> instead of <link> to embed CSS directly

(function() {
    'use strict';
    const head = document.getElementsByTagName('head')[0];
    if(head.querySelector('style:not(:empty), link[rel~=stylesheet]') === null) {
        head.insertAdjacentHTML('beforeend', '<link rel="stylesheet" href="https://unpkg.com/spcss" />');
    }
})();