Best UI design prompts: 11 libraries, measured

A UI design prompt is worth exactly what it decides for you. The rest of what you are paying for is packaging.

Eleven libraries sell these today. They run from $12 a month to $399 once, and the price predicts almost nothing about which one leaves you with a page worth shipping. The thing that separates them is how much of the design is already settled when the file lands: hex values with a role each, a type scale in px, an easing curve with a real duration, and the order the sections run in.

The short version, before the detail:

• Want the longest and most specific artefacts? MotionSites, Webthemez and Meez write the deepest prompts in the category.
• Want one coherent motion language instead of a catalogue of effects? Scrolltide and CloneWeb both name curves and delays as real values.
• Want to judge before you pay? BuildPromptKit, NightMarquee and Webthemez give away enough to do that properly.
• Want the decisions themselves across a whole library, written as values rather than adjectives? That is what Thanor sells.

What separates one library from another#

Four things, and price is not one of them.

1. Whether it names values. This is the whole game. cubic-bezier(0.22, 1, 0.36, 1) at 750ms is a decision. "Smooth, modern animations" asks the model to decide, and the model decides the same way every time.
2. How long the prompt runs. Length is a proxy for specificity, because you cannot name a palette, a scale, a curve and a section order in a paragraph. A rough proxy: a long prompt can be adjectives with more words.
3. What you can read before paying. A library that publishes complete prompts lets you check the first two points in ten minutes. One that publishes none is asking you to buy the wrapper.
4. What the refund says. It ranges from fourteen days no questions to "All sales are final", and it is written down on every one of these sites before you hand anything over.

The first of those is the one that survives contact with a real page. The rest tell you how much risk you are taking to find out.

The eleven, side by side#

Sorted by typical prompt length, longest first, because that is the one column you can verify yourself by opening a free item.

The six that give you values#

MotionSites. The deepest artefacts in the category. Each item carries a looping video of the result and the prompt references it, which is why output tends to resemble the preview you clicked. Inside: exact HSL channel values for every CSS variable, exact class strings, and timings written as "500ms fade-out when 0.55 seconds remain". It also runs an MCP server, and three prompts come through it free, so the cheapest MotionSites alternative is MotionSites.

Webthemez. Twelve years of domain age behind it, which nobody else here has. The prompts carry exact hex, an exact type scale, negative margins and scroll-linked numeric ranges with named easings and durations. It also pins the exact asset URLs it wants you to use, with an instruction to use them. Swap those out before you ship, because otherwise your site serves media from somebody else's storage.

CloneWeb. The cleanest commercial architecture in the set, and a brief skeleton of twelve to fourteen sections that ends in acceptance criteria rather than in a vibe. The sample prompt names animation delays at 100ms, 220ms, 340ms and 460ms, an IntersectionObserver threshold of 0.15, a scroll lerp constant of 0.1 and a device-pixel-ratio cap of 2.

Meez. The largest catalogue here, at 926 items: 641 prompts and 285 animated backgrounds, every one with a real page behind it. Prompts use semantically named hex tokens, clamp() expressions, per-element delays in seconds and typed easing constants. Sixty-two complete prompts are free with no email, which makes it the easiest large library to evaluate.

Scrolltide. One motion language applied across everything, rather than a catalogue of unrelated effects. It publishes a single sitewide easing curve, cubic-bezier(0.22, 1, 0.36, 1), a 750ms entry, a 60ms stagger, a prefers-reduced-motion gate and a 4.5:1 contrast floor. It is also the only one that ships a named Restraint axis alongside layout, typography, motion and depth.

BuildPromptKit. Free to start, $29 for lifetime access. Its flagship item is the single best artefact in this group: three named responsive layout modes, embedded fonts, measured timings, and a closing verification log that reports an entrance handoff at 72ms and a release at 1880ms. Every item has a working self-hosted demo that states its own deviations in a comment.

The five shorter ones#

• Kinemble. $39 once. Built first, described after, which shows in the detail: the flagship is a 302-frame scroll-scrub sequence that could not have been faked. Prompts average around 545 words.
• NightMarquee. $12 a month or $79 a year. Thirty-six prompts, each genuinely rewritten into four per-tool variants rather than find-and-replaced, with thirty-six hand-coded full-page demos on its own domain. It carries a fourteen-day no-questions refund, the most restrained commercial posture in the group.
• SitePrompts. $199 a year. Shorter prompts, but the constraint block is a genuinely original idea: a list of what the design may not do, which is the half of direction most libraries leave out.
• 3dwebsitesai. $45 a month. Free, real, scrollable demos, and hosted media referenced by absolute URL inside the prompt. Its terms read "All sales are final", so treat the free demos as the whole of your evaluation.
• AdsWebAI. $19 a month. The best interface in the category, with a command palette over the whole catalogue. The prompts themselves are short, closer to a well-written brief line than to a specification.

What a table cannot score#

Whether the values are the right values. Six of these name durations, and they do not agree with each other. Scrolltide enters at 750ms. Webflow's public guidance puts entrances at 500ms to 800ms and microinteractions at 150ms to 300ms. Anthropic's published design guidance argues for motion used sparingly and names the fade-and-slide-up entrance on every section as a tell. A column can score "names a duration". It cannot score "names a good one".

Whether a thousand buyers produce a thousand identical sites. Nothing in this category addresses it, and it is the structural problem underneath all of it. The answer is not longer prompts. It is prompts that force a different decision each time rather than handing everyone the same finished look.

What you are actually buying. Some catalogues in this space resell components that are MIT licensed and already free. Before you pay, open one complete item and ask whether you are buying direction or a rewrapped package you could install yourself.

What to buy, by what you are short of#

• Short of components? None of these. Free component libraries do that job and they do it better, at zero.
• Short of a finished page this afternoon? MotionSites, Webthemez or 3dwebsitesai. Working demos, pinned media, fast to a result.
• Short of a motion language that holds together? Scrolltide or CloneWeb.
• Short of budget? BuildPromptKit at $29 or Kinemble at $39, and take the free tiers at NightMarquee and Meez first.
• Short of the decisions themselves? That is the harder gap and the one that keeps showing up on the second revision, when somebody has to say what the curve is, what the scale is and what the page refuses to do.

That last one is what Thanor is built around: a library of full art direction per design, written as exact values rather than adjectives, for personal and client work alike. $89 for three months, $189 a year, $299 once. Free accounts open the designs marked free, so you can read a complete one before deciding.

Go and read one. It is the only honest way to judge any library on this page, including ours.