A dark theme Swagger UI never shipped

Swagger UI is the de-facto renderer for OpenAPI documentation — and it still has no official dark mode. OASForge started life as exactly that: a carefully engineered dark theme for Swagger UI 5, and grew into a full workbench around it.

Not a color-inverted hack

Most dark Swagger themes invert colors or slap a filter on the page, which breaks method badges, code samples and syntax highlighting. OASForge's theme is built as a token-based stylesheet: every color in Swagger UI's rendering — operation blocks, schema trees, models, code snippets, "Try it out" forms — maps to a design token, so the dark palette stays readable and the method colors (GET, POST, DELETE…) keep their meaning.

Four palettes, light mode included

The default dark palette follows the GitHub-dark family; Nord, Dracula and Catppuccin palettes ship alongside it, plus a light mode toggle. Your choice persists in the browser.

Use it two ways

• In OASForge: paste your OpenAPI description into the editor and the preview renders in the dark theme immediately — nothing to install.
• In your own docs: the theme is a plain CSS file (css/theme.css) in the source repository, written for Swagger UI 5.x and source-available under ELv2 — free to use in your products.

The exported standalone HTML docs use the same styling, so documentation you hand to a customer looks the way it does in the editor.