Interfaces succeed because of hundreds of choices. This is a living, non-exhaustive list of those decisions. Most guidelines are framework-agnostic, some specific to React/Next.js. Feedback is welcome.

• Keyboard works everywhere. All flows are keyboard-operable & follow the WAI-ARIA Authoring Patterns.
• Clear focus. Every focusable element shows a visible focus ring. Prefer :focus-visible over :focus to avoid distracting pointer users. Set :focus-within for grouped controls.
• Manage focus. Use focus traps, move & return focus according to the WAI-ARIA Patterns.
• Match visual & hit targets. Exception: if the visual target is < 24px, expand its hit target to ≥ 24px. On mobile, the minimum size is 44px.
• Mobile input size. <input> font size is ≥ 16px on mobile to prevent iOS Safari auto-zoom/pan on focus. Or set <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1" />.
• Respect zoom. Never disable browser zoom.
• Hydration-safe inputs. Inputs must not lose focus or value after hydration.
• Don’t block paste. Never disable paste in <input> or <textarea>.
• Loading buttons. Show a loading indicator & keep the original label.
• Minimum loading-state duration. If you show a spinner/skeleton, add a short show-delay (~150–300 ms) & a minimum visible time (~300–500 ms) to avoid flicker on fast responses. The <Suspense> component in React does this automatically.
• URL as state. Persist state in the URL so share, refresh, Back/Forward navigation work e.g., nuqs.
• Optimistic updates. Update the UI immediately when success is likely; reconcile on server response. On failure, show an error & roll back or provide Undo.
• Ellipsis for further input & loading states. Menu options that open a follow-up e.g., "Rename…" & loading/processing states e.g., "Loading…", "Saving…", "Generating…" end with an ellipsis.
• Confirm destructive actions. Require confirmation or provide Undo with a safe window.
• Prevent double-tap zoom on controls. Set touch-action: manipulation.
• Tap highlight follows design. Set webkit-tap-highlight-color.
• Design forgiving interactions. Controls minimize finickiness with generous hit targets, clear affordances, & predictable interactions, e.g., prediction cones.
• Tooltip timing. Delay the first tooltip in a group; subsequent peers have no delay.
• Overscroll behavior. Set overscroll-behavior: contain intentionally e.g., in modals/drawers.
• Scroll positions persist. Back/Forward restores prior scroll.
• Autofocus for speed. On desktop screens with a single primary input, autofocus. Rarely autofocus on mobile because the keyboard opening can cause layout shift.
• No dead zones. If part of a control looks interactive, it should be interactive. Don’t leave users guessing where to interact.
• Deep-link everything. Filters, tabs, pagination, expanded panels, anytime useState is used.
• Clean drag interactions. Disable text selection & apply inert (which prevents interaction) while an element is dragged so selection/hover don't occur simultaneously.
• Links are links. Use <a> or <Link> for navigation so standard browser behaviors work (Cmd/Ctrl+Click, middle-click, right-click to open in a new tab). Never substitute with <button> or <div> for navigational links.
• Announce async updates. Use polite aria-live for toasts & inline validation.
• Locale-aware keyboard shortcuts. Internationalize keyboard shortcuts for non-QWERTY layouts. Show platform-specific symbols.

• Honor prefers-reduced-motion. Provide a reduced-motion variant.
• Implementation preference. Prefer CSS, avoid main-thread JS-driven animations when possible.
  • Preference: CSS > Web Animations API > JavaScript libraries e.g., motion.
• Compositor-friendly. Prioritize GPU-accelerated properties (transform, opacity) & avoid properties that trigger reflows/repaints (width, height, top, left).
• Necessity check. Only animate when it clarifies cause & effect or when it adds deliberate delight e.g., the northern lights.
• Easing fits the subject. Choose easing based on what changes (size, distance, trigger).
• Interruptible. Animations are cancelable by user input.
• Input-driven. Avoid autoplay; animate in response to actions.
• Correct transform origin. Anchor motion to where it “physically” starts.
• Never transition: all. Explicitly list only the properties you intend to animate (typically opacity, transform). all can unintentionally animate layout-affecting properties causing jank.
• Cross-browser SVG transforms. Apply CSS transforms/animations to <g> wrappers & set transform-box: fill-box; transform-origin: center;. Safari historically had bugs with transform-origin on SVG & grouping avoids origin miscalculation.

• Optical alignment. Adjust ±1px when perception beats geometry.
• Deliberate alignment. Every element aligns with something intentionally whether to a grid, baseline, edge, or optical center. No accidental positioning.
• Balance contrast in lockups. When text & icons sit side by side, adjust weight, size, spacing, or color so they don’t clash. For example, a thin-stroke icon may need a bolder stroke next to medium-weight text.
• Responsive coverage. Verify on mobile, laptop, & ultra-wide. For ultra-wide, zoom out to 50% to simulate.
• Respect safe areas. Account for notches & insets with safe-area variables.
• No excessive scrollbars. Only render useful scrollbars; fix overflow issues to prevent unwanted scrollbars. On macOS set "Show scroll bars" to "Always" to test what Windows users would see.
• Let the browser size things. Prefer flex/grid/intrinsic layout over measuring in JS. Avoid layout thrash by letting CSS handle flow, wrapping, & alignment.

• Inline help first. Prefer inline explanations; use tooltips as a last resort.
• Stable skeletons. Skeletons mirror final content exactly to avoid layout shift.
• Accurate page titles. <title> reflects the current context.
• No dead ends. Every screen offers a next step or recovery path.
• All states designed. Empty, sparse, dense, & error states.
• Typographic quotes. Prefer curly quotes (“ ”) over straight quotes (" ").
• Avoid widows/orphans. Tidy rag & line breaks.
• Tabular numbers for comparisons. Use font-variant-numeric: tabular-nums or a monospace like Geist Mono.
• Redundant status cues. Don’t rely on color alone; include text labels.
• Icons have labels. Convey the same meaning with text for non-sighted users.
• Don’t ship the schema. Visual layouts may omit visible labels, but accessible names/labels still exist for assistive tech.
• Use the ellipsis character. … over three periods ....
• Anchored headings. Set scroll-margin-top for headers when linking to sections.
• Resilient to user-generated content. Layouts handle short, average, & very long content.
• Locale-aware formats. Format dates, times, numbers, delimiters, & currencies for the user’s locale.
• Prefer language settings over location. Detect language via Accept-Language header & navigator.languages. Never rely on IP/GPS for language.
• Shield verbatim content from translation. Wrap brand names, product names, code tokens, & technical identifiers with translate="no" so browser auto-translate leaves them intact.
• Accessible content. Set accurate names (aria-label), hide decoration (aria-hidden) & verify in the accessibility tree.
• Icon-only buttons are named. Provide a descriptive aria-label.
• Semantics before ARIA. Prefer native elements (button, a, label, table), before aria-*.
• Headings & skip link. Hierarchical <h1–h6> & a “Skip to content” link.
• Brand resources from the logo. Right-click the nav logo to surface brand assets for quick access.
• Non-breaking spaces for glued terms. Use a non-breaking space   to keep units, shortcuts & names together: 10 MB → 10 MB, ⌘ + K → ⌘ + K, Vercel SDK → Vercel SDK. Use ⁠ for no space.

• Enter submits. When a text input is focused, Enter submits if it's the only control. If there are many controls, apply to the last control.
• Textarea behavior. In <textarea>, ⌘/⌃+Enter submits; Enter inserts a new line.
• Labels everywhere. Every control has a <label> or is associated with a label for assistive tech.
• Label activation. Clicking a <label> focuses the associated control.
• Submission rule. Keep submit enabled until submission starts; then disable during the in-flight request, show a spinner, & include an idempotency key.
• Don’t block typing. Even if a field only accepts numbers, allow any input & show validation feedback. Blocking keystrokes entirely is confusing because the user gets no explanation.
• Don’t pre-disable submit. Allow submitting incomplete forms to surface validation feedback.
• No dead zones on controls. Checkboxes & radios avoid dead zones; the label & control share a single generous hit target.
• Error placement. Show errors next to their fields; on submit, focus the first error.
• Autocomplete & names. Set autocomplete & meaningful name values to enable autofill.
• Spellcheck selectively. Disable for emails, codes, usernames, etc.
• Correct types & input modes. Use the right type & inputmode for better keyboards & validation.
• Placeholders signal emptiness. End with an ellipsis.
• Placeholder value. Set placeholder to an example value or pattern e.g., +1 (123) 456-7890 & sk-012345679…
• Unsaved changes. Warn before navigation when data could be lost.
• Password managers & 2FA. Ensure compatibility & allow pasting one-time codes.
• Don’t trigger password managers for non-auth fields. For inputs like “Search” avoid reserved names (e.g., password), use autocomplete="off" or a specific token like autocomplete="one-time-code" for OTP fields.
• Text replacements & expansions. Some input methods add trailing whitespace. The input should trim the value to avoid showing a confusing error message.
• Windows <select> background. Explicitly set background-color & color on native <select> to avoid dark-mode contrast bugs on Windows.

• Device/browser matrix. Test iOS Low Power Mode & macOS Safari.
• Measure reliably. Disable extensions that add overhead or change runtime behavior.
• Track re-renders. Minimize & make re-renders fast. Use React DevTools or React Scan.
• Throttle when profiling. Test with CPU & network throttling.
• Minimize layout work. Batch reads/writes; avoid unnecessary reflows/repaints.
• Network latency budgets. POST/PATCH/DELETE complete in <500ms.
• Keystroke cost. Prefer uncontrolled inputs; make controlled loops cheap.
• Large lists. Virtualize large lists e.g., virtua or content-visibility: auto.
• Preload wisely. Preload only above-the-fold images; lazy-load the rest.
• No image-caused CLS. Set explicit image dimensions & reserve space.
• Preconnect to origins. Use <link rel="preconnect"> for asset/CDN domains (with crossorigin when needed) to reduce DNS/TLS latency.
• Preload fonts. For critical text to avoid flash & layout shift.
• Subset fonts. Ship only the code points/scripts you use via unicode-range (limit variable axes to what you need) to shrink size.
• Don’t use the main thread for expensive work. Move especially long tasks to Web Workers to avoid blocking interaction with the page.

• Layered shadows. Mimic ambient + direct light with at least two layers.
• Crisp borders. Combine borders & shadows; semi-transparent borders improve edge clarity.
• Nested radii. Child radius ≤ parent radius & concentric so curves align.
• Hue consistency. On non-neutral backgrounds, tint borders/shadows/text toward the same hue.
• Accessible charts. Use color-blind-friendly palettes.
• Minimum contrast. Prefer APCA over WCAG 2 for more accurate perceptual contrast.
• Interactions increase contrast. :hover, :active, :focus have more contrast than rest state.
• Browser UI matches your background. Set <meta name="theme-color" content="#000000"> to align the browser’s theme color with the page background.
• Set the appropriate color-scheme. Style the <html> tag with color-scheme: dark in dark themes so that scrollbars and other device UI have proper contrast.
• Text anti-aliasing & transforms. Scaling text can change smoothing. Prefer animating a wrapper instead of the text node. If artifacts persist set translateZ(0) or will-change: transform to promote to its own layer.
• Avoid gradient banding. Fading content to dark colors using css masks can cause banding. Background images can be used instead.

These preferences reflect Vercel’s brand & product choices. They aren’t universal guidelines.

• Active voice.
  • Instead of “The CLI will be installed,” say “Install the CLI.”
• Headings & buttons use Title Case (Chicago). On marketing pages, use sentence case.
• Be clear & concise. Use as few words as possible.
• Prefer & over and.
• Action-oriented language.
  • Instead of “You will need the CLI…” say “Install the CLI…”.
• Keep nouns consistent. Introduce as few unique terms as possible.
• Write in second person. Avoid first person.
• Use consistent placeholders.
  • Strings: YOUR_API_TOKEN_HERE. Numbers: 0123456789.
• Use numerals for counts.
  • Instead of “eight deployments” say “8 deployments”.
• Consistent currency formatting. In any given context, display currency with either 0 or 2 decimal places, never mix both.
• Separate numbers & units with a space.
  • Instead of 10MB say 10 MB.
  • Use a non-breaking space e.g., 10 MB.
• Default to positive language. Frame messages in an encouraging, problem-solving way, even for errors.
  • Instead of “Your deployment failed,” say “Something went wrong—try again or contact support.”
• Error messages guide the exit. Don’t just state what went wrong—tell the user how to fix it.
  • Instead of “Invalid API key,” say “Your API key is incorrect or expired. Generate a new key in your account settings.” The copy & buttons/links should educate & give a clear action.
• Avoid ambiguity. Labels are clear & specific.
  • Instead of the button label “Continue” say “Save API Key”.

Use these guidelines with AI coding agents. Audit all generated interfaces.

Install /web-interface-guidelines to review UI code:

curl -fsSL https://vercel.com/design/guidelines/install | bash

Supports Antigravity, Claude Code, Cursor, Gemini CLI, OpenCode, & Windsurf.

For other agents, use the command prompt directly.

Add AGENTS.md to your project so agents apply these guidelines during generation.

• Download AGENTS.md

We’re hiring people who live for these details. Check out the job postings.

Thanks to Adam, Jimmy, Jonnie, Lochie, Paco, Joe, & Austin for feedback.