Codex Design vs tweakcn.
tweakcn and the Codex Design design system library both help an AI-built app stop looking like every other shadcn app. tweakcn is a visual editor for shadcn/ui themes. Our library is a set of complete design systems for websites and mobile apps, written so that Codex or Claude Code can follow them, with a shadcn theme for each.
Updated November 6, 2026 · 5 min read
The short answer
If you want to tune a shadcn theme by hand, color by color, or generate one from an image, use tweakcn. If you want an AI agent to follow a complete design system, with type scale, layout rules, and what to avoid, for a website or a mobile app, start from the Codex Design library.
- Choose tweakcn if you want hands-on control of every shadcn variable with a live preview, a large set of community themes, or AI generation from a prompt or image.
- Choose the Codex Design library if you design with Codex or Claude Code, need guidance for mobile apps as well as web, or want each system as a DESIGN.md your agent saves and follows.
What each tool is
tweakcn is an open-source visual theme editor for Tailwind CSS and shadcn/ui, made by Sahaj (jnsahaj on GitHub). You start from a preset, adjust colors, typography, radius, spacing, and shadows with a real-time preview and a contrast checker, and export the theme as CSS variables or a shadcn registry command. It supports Tailwind v4 and v3, in OKLCH or HSL. Its Pro plan adds unlimited AI theme generation, including from images.
The Codex Design library is a free collection of design systems on this site, each with colors for light and dark mode, Google Fonts, a type scale, radius, spacing, shadows, and rules for using them. Every system has a live preview, a DESIGN.md that an agent can read from its URL, a globals.css for Tailwind v4, and a shadcn theme you install with one command. Half of them are built for mobile apps, with touch targets, a tab bar, and screen padding.
Side by side
| tweakcn | Codex Design library | |
|---|---|---|
| What you get | A shadcn theme you build or pick from presets and community themes | Complete design systems: tokens plus type scale, layout, and do’s and don’ts |
| Editing | Visual editor with real-time preview | Copy as is, or ask your agent to change it |
| Web and app | shadcn/ui themes for web apps | 12 web systems and 12 mobile app systems |
| For AI agents | Export CSS or a registry command | DESIGN.md at a public URL, a one-line prompt, CSS, and a shadcn registry command |
| AI generation | 5 AI themes free; unlimited, and from images, on Pro | None; systems are designed and checked for contrast by hand |
| Pricing | Free; Pro is $8 a month | Free |
| Open source | Yes (Apache 2.0) | No; the systems are free to copy and use |
Facts as of November 6, 2026, from tweakcn.com and its GitHub repository.
When to choose tweakcn
tweakcn is the better tool when you want to shape a theme yourself. Every shadcn variable is a slider or color picker, the preview updates as you change it, and the community gallery gives you many starting points. If you already have brand colors and want to see them across shadcn components before you commit, it’s faster than editing CSS by hand.
When to choose the Codex Design library
A theme sets colors, fonts, and radius, but an agent also needs to know how big the headings are, how wide the text runs, how much space goes between sections, and which patterns to avoid. Each system in our library writes that down in a DESIGN.md, so Codex or Claude Code applies it to every screen, not only to shadcn components. App systems add the rules phone screens need, such as 48px touch targets and a bottom tab bar. And because the systems avoid patterns that read as AI-made, such as purple gradients and glassmorphism, they are a safer starting point when you don’t want your product to look generated.
Frequently asked questions
Is the Codex Design library a tweakcn alternative?
For picking a starting theme, yes: every system installs as a shadcn theme with one command. For editing a theme visually, tweakcn does more; our library is meant to be followed by an AI agent.
Can I use both?
Yes. Pick a system from our library, install its shadcn theme, and fine-tune the colors in tweakcn. Then ask your agent to update the DESIGN.md to match.
Do I need the Codex Design plugin to use the library?
No. The design systems are free on this site and work in any project. The Codex Design plugin adds a canvas for comparing design directions in Codex.