How to override styles of a third-party UI library if important, ID, and inline styles do not work?

If standard style override methods (important, ID, inline styles) do not help, the library probably uses Shadow DOM, CSS-in-JS with high specificity, or styles with very high priority.

Possible approaches:

• Use Shadow DOM slots or CSS Custom Properties: if the library uses Shadow DOM, try overriding styles through CSS variables or slots.
• Override via JavaScript: dynamically change styles using JS, for example, by adding classes or changing element styles after rendering.
• Use more specific selectors: for example, combine selectors with attributes, pseudo-classes, nesting to increase specificity.
• Use CSS Variables (Custom Properties): if supported by the library, change the variable values.
• Fork or customize the library: if nothing helps, you can fork the library and change styles directly.

Example of increasing specificity:

/* Instead of simple .button */
div.container > .button.special {
  color: red !important;
}

If the library uses Shadow DOM, styles from external CSS will not apply directly, so you need to look for the library's API for customization or use JavaScript to access shadowRoot and change styles there.