Hi @GeorgeO — there's no native way to conditionally swap Knowledge Blocks based on light/dark theme, but the better fix is likely upstream in how the CSS is written rather than swapping blocks.
The cleanest approach: replace hard-coded color values in your block CSS with CSS custom properties that respond to the user's theme automatically.
For example, instead of:
color: #1a1a1a;
Use:
color: var(--now-color--neutral-18, #1a1a1a);
Now UX ships a full set of CSS variables (--now-color--, --now-color-text--, etc.) that flip automatically between light and dark theme. If your blocks reference those instead of hex values, they adapt without any conditional logic.
If swapping blocks is still the direction you want to go, you could embed a small inline script in a block that checks document.documentElement and shows/hides content based on the active theme class — but that's fragile and not something ServiceNow supports officially.
Worth auditing the hard-coded values first — in most cases replacing 3-4 color declarations fixes the problem across all your blocks at once.
Note: CSS variable names have shifted across releases, so it's worth verifying the exact token names against the Now Design System docs for your release before updating your blocks. The pattern is consistent but specific variable names may differ.
