Pick the outcome, not the model
Every AI builder starts the same way: you choose a model, write a prompt, wait, and hope it read your mind. If the result is off, you can never tell whether the idea was wrong or the model was wrong for the job. You were betting on one horse before the race even started.
Benchmarks do not help here. They tell you which model is good on average, across tasks that are not yours. They cannot tell you which model is good at this screen, with this brief, in this style, right now. The only honest way to know is to see the work.
So 21st AI stops asking you to choose up front. You describe your idea once, and every frontier model builds it at the same time. You get a wall of real takes, side by side, and you keep the one that actually nailed it. You are choosing an outcome you can see, not a reputation you have to trust.
Every model, one brief, in parallel
When you send a prompt, we do not route it to a single model. We fan it out. Each model gets the same brief and produces its own independent take, and they all generate concurrently, not one after another. The fast ones show up first and start rendering while the others are still thinking, so the grid fills in live instead of making you wait for the slowest one.
The takes are deliberately anonymous. You see "Take 1", "Take 2", "Take 3", never a model name or a logo. That is the whole point: we do not want you picking the take with the trendiest brand on it. We want you picking the one that looks right. Model identity is a distraction from the only question that matters, which is does this look like what I wanted.
Under the hood each take is its own generation stream. We hold a per-take lock so the same take never double-generates, meter each one independently, and validate the output before it lands: if a model returns a truncated or broken draft, that take retries with an explicit "return the complete thing" instruction before it gives up. One model stumbling never blocks the others.
Sketch mode: drafts you can see in under a second
The default mode is Sketch. Instead of spinning up a sandbox, resolving dependencies, and running a build, a sketch is a single self-contained HTML document styled with Tailwind, rendered live in an iframe. There is no build step between the model and the pixels.
That means the draft streams in token by token. As the model writes markup, we clean the stream on the fly (stripping stray code fences and partial tags) and paint it straight into the preview on a smooth cadence, so you watch the layout assemble in real time rather than staring at a spinner. From prompt to a living, scrollable draft is usually under a second per take.
Sketches are throwaway on purpose. They are fast, cheap, and disposable, so comparing four of them costs you almost nothing and you never get attached to a draft you are about to discard.
Your taste is part of the input
A blank model starts from nothing and drifts toward generic. So 21st AI does not start blank. Two kinds of context ground every take:
Community components as structural cues
When you write a brief, we run a semantic search across the 21st catalog and pull the components that actually match what you are describing. Those references are handed to every model as structural inspiration, not copy-paste: "here are real, shipped 21st components close to this idea, take cues from how they are built." The grounding is retrieved once when the project is created and carried forward to every take and every refine, so all the models are pointed in the same direction instead of each inventing its own.
Community themes as exact tokens
Pick a published community theme and its design tokens (primary, background, foreground, accent, muted, border, radius, font) are injected into the prompt as explicit instructions with the real hex and OKLCH values. The models do not guess your palette, they are told it. A theme is the difference between "a pricing page" and "a pricing page that looks like it belongs in your product."
And if you start from an existing component (a remix), that component's own code goes in as the reference, so the takes build on what you already have instead of starting over.
Keep the best, hand it to your agent
Once a take clicks, you have two ways forward.
Iterate. Type a refinement in plain language ("make the header sticky", "tighten the spacing", "give it a dark variant"). Refines are surgical: we try a targeted search-and-replace edit on the existing draft first, which is an order of magnitude cheaper and faster than a full rewrite, and only fall back to regenerating from scratch if the diff cannot be applied. Every refine is kept as a version, so you can tab back through "Initial draft", "Refine 1", "Refine 2" and never lose a good state.
Copy the prompt and hand it off. This is free and unlimited. "Copy prompt" does not dump the raw HTML at your agent. It builds a proper handoff: a two-step instruction that first tells your agent to inspect your project's real stack (framework, styling, design tokens, existing components) and then recreate the sketch using your stack and your components, with the sketch wrapped as a reference rather than something to paste verbatim. It even lists the grounding components with ready-to-run npx @21st-dev/cli add commands, so your agent installs the real thing instead of reimplementing it.
The result is a clean division of labor. 21st AI is where you explore the design space and decide the direction. Your own agent, in your own repo, is where it gets built for real. No lock-in, no "export and pray."
Why compare at all
The best model for your idea is not the one at the top of a leaderboard. It is the one whose take you actually want to ship, and that changes from screen to screen. One model nails layout and fumbles motion. Another writes clean structure and flat visuals. You feel none of that from a spec sheet. You feel it the instant you see four takes next to each other.
That is the bet behind 21st AI: not that any single model is best, but that seeing them all beats guessing at any of them. Describe your idea once, let them all pitch you, and keep the winner.