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Token-only typography for rendered rich text, with section links and code copy.

Text & contentmotion

01Preview

Verifying webhook signatures

Every webhook carries a signature, so you can check it came from Northwind and wasn’t changed on the way. Verify it before you trust anything in the body.

How signing works

We compute an HMAC-SHA256 of the raw request body with your endpoint’s secret and send it in the Northwind-Signature header, next to a timestamp. The security overview covers how secrets are stored.

  1. Read the raw body before any JSON parsing.
  2. Build the signed payload as {timestamp}.{body}.
  3. Compare it to the header in constant time.
import { createHmac, timingSafeEqual } from "node:crypto";

export function verify(body: string, header: string, secret: string) {
  const [timestamp, signature] = header.split(",");
  const expected = createHmac("sha256", secret).update(`${timestamp}.${body}`).digest("hex");
  // Constant time, so the comparison can't leak how much of it matched.
  return timingSafeEqual(Buffer.from(signature), Buffer.from(expected));
}

Rotating a secret? The old one keeps working for 24 hours, so a deploy never drops events. Press ⌘ K and search for “webhooks” to find it.

Retry schedule

Failed deliveries retry with exponential backoff for up to three days, then the endpoint is paused and you get an email.

AttemptDelayElapsed
1Immediately0 s
230 s30 s
35 min5.5 min
430 min36 min
52 h2.6 h
612 h14.6 h
An analytics dashboard with delivery charts on a laptop screen
Each retry shows up in the delivery log within a few seconds, with the response your server sent.

Before you go live

  • Keep the secret out of source control
  • Reject timestamps older than five minutes
  • Respond with a 2xx within 10 seconds, then do the work
Why compare in constant time?

A normal comparison stops at the first different character, so how long it takes reveals how much of a forged signature was right. Constant time takes the same time either way.

02Install

Copy the source into your project. It becomes yours: no package to update, no wrapper between you and the markup. It needs:

npm install motion

03Usage

import { Prose } from "@/components/ui/prose";

// Children from MDX or a markdown renderer
<Prose>
  <MDXContent />
</Prose>

// Or sanitized HTML from a CMS, at a size that fits where it lives
<Prose size="sm" html={comment.bodyHtml} />

04Source

"use client";
import { AnimatePresence, motion, useReducedMotion } from "motion/react";
import { useCallback, useEffect, useRef, useState } from "react";
import { CopyButton, useCopy } from "@/components/ui/copy-button";
import { cn } from "@/lib/cn";
import { ease } from "@/lib/motion";
import { Check, Link as LinkIcon } from "@/lib/icons";

/* -------------------------------------------------------------------------------------------------
 * Type
 *
 * Every rule sits inside :where(), so it has no specificity: a class on any element inside
 * wins without a fight. Sizes are three sets of custom properties, so the rhythm (flow space,
 * heading steps, code size) scales as one system instead of being re-declared per size.
 * -----------------------------------------------------------------------------------------------*/

const ARROW =
  "url(\"data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='none' stroke='currentColor' stroke-width='1.6' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M5 11 11 5M6 5h5v5'/%3E%3C/svg%3E\")";
const CHEVRON =
  "url(\"data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='none' stroke='currentColor' stroke-width='1.6' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6.25 4.5 3.5 3.5-3.5 3.5'/%3E%3C/svg%3E\")";
const TICK =
  "url(\"data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M3.5 8.5 6.5 11.5 12.5 4.5'/%3E%3C/svg%3E\")";

const CSS = `
[data-prose]{--p-size:15px;--p-lh:1.65;--p-h1:28px;--p-h2:20px;--p-h3:16.5px;--p-h4:15px;--p-code:12.5px;--p-flow:1.05em;
  --sh-keyword:var(--fg);--sh-class:var(--fg);--sh-entity:var(--fg);--sh-identifier:var(--fg);--sh-property:var(--fg-2);--sh-string:var(--fg-2);--sh-jsxliterals:var(--fg-2);--sh-sign:var(--fg-3);--sh-comment:var(--fg-4);
  position:relative;font-size:var(--p-size);line-height:var(--p-lh);color:var(--fg-2);overflow-wrap:break-word}
[data-prose][data-size=sm]{--p-size:13.5px;--p-lh:1.6;--p-h1:20px;--p-h2:16px;--p-h3:14px;--p-h4:13.5px;--p-code:12px;--p-flow:.9em}
[data-prose][data-size=lg]{--p-size:17px;--p-lh:1.7;--p-h1:34px;--p-h2:24px;--p-h3:19px;--p-h4:17px;--p-code:13.5px;--p-flow:1.15em}
[data-prose][data-measure]{max-width:68ch}

:where([data-prose-body]) :where(h1,h2,h3,h4,h5,h6,p,ul,ol,dl,pre,blockquote,table,figure,hr,details,img,video){margin:var(--p-flow) 0 0}
:where([data-prose-body]) > :first-child,:where([data-prose-body]) :where(li,blockquote,dd,figure,details) > :first-child{margin-top:0}

:where([data-prose-body]) :where(h1,h2,h3,h4,h5,h6){color:var(--fg);font-weight:500;text-wrap:balance;scroll-margin-top:5rem}
:where([data-prose-body]) :where(h1){font-size:var(--p-h1);line-height:1.15;letter-spacing:-.025em;font-weight:600}
:where([data-prose-body]) :where(h2){font-size:var(--p-h2);line-height:1.3;letter-spacing:-.02em;margin-top:1.9em}
:where([data-prose-body]) :where(h3){font-size:var(--p-h3);line-height:1.4;letter-spacing:-.012em;margin-top:1.8em}
:where([data-prose-body]) :where(h4,h5,h6){font-size:var(--p-h4);line-height:1.45;letter-spacing:-.005em;margin-top:1.6em}
:where([data-prose-body]) :where(h1,h2,h3,h4,h5,h6) + *{margin-top:.55em}
:where([data-prose-body]) :where(h1) + *{margin-top:.8em}
:where([data-prose-body]) :where(p,li,dd,blockquote,figcaption){text-wrap:pretty}
:where([data-prose-body]) :where(strong,b){color:var(--fg);font-weight:500}
:where([data-prose-body]) :where(small){font-size:.86em}
:where([data-prose-body]) :where(mark){color:var(--fg);background:color-mix(in oklab,var(--fg) 12%,transparent);border-radius:3px;padding:0 .15em;box-decoration-break:clone;-webkit-box-decoration-break:clone}
:where([data-prose-body]) :where(abbr[title]){text-decoration:underline dotted var(--fg-4);text-underline-offset:3px;cursor:help}
:where([data-prose-body]) :where(sub,sup){font-size:.75em;line-height:0}
:where([data-prose-body]) :where(sup a){font-family:var(--font-mono);text-decoration:none;padding:0 .1em}

:where([data-prose-body]) :where(a){color:var(--fg);text-decoration:underline;text-decoration-color:var(--fg-4);text-decoration-thickness:1px;text-underline-offset:3px;border-radius:3px;transition:text-decoration-color .16s ease-out}
:where([data-prose-body]) :where(a):hover{text-decoration-color:var(--fg-2)}
:where([data-prose-body]) :where(a):focus-visible{outline:1px solid var(--fg-3);outline-offset:2px}
:where([data-prose-body]) :where(a[target=_blank])::after{content:"";display:inline-block;width:.72em;height:.72em;margin-left:.12em;vertical-align:.02em;background:currentColor;opacity:.45;-webkit-mask:${ARROW} center/contain no-repeat;mask:${ARROW} center/contain no-repeat;transition:translate .2s var(--ease-out-expo),opacity .16s ease-out}
:where([data-prose-body]) :where(a[target=_blank]):hover::after{translate:1px -1px;opacity:.9}

:where([data-prose-body]) :where(ul,ol){padding-left:1.35em}
:where([data-prose-body]) :where(ul){list-style:disc}
:where([data-prose-body]) :where(ol){list-style:decimal}
:where([data-prose-body]) :where(ul ul){list-style:circle}
:where([data-prose-body]) :where(li){margin-top:.3em;padding-left:.2em}
:where([data-prose-body]) :where(li)::marker{color:var(--fg-4)}
:where([data-prose-body]) :where(ol > li)::marker{font-variant-numeric:tabular-nums;color:var(--fg-3)}
:where([data-prose-body]) :where(li > ul,li > ol){margin-top:.3em}
:where([data-prose-body]) :where(li:has(> input[type=checkbox])){list-style:none;margin-left:-1.3em;padding-left:0}
:where([data-prose-body]) :where(li > input[type=checkbox]){appearance:none;width:.9em;height:.9em;margin:0 .45em 0 0;vertical-align:-.1em;border:1px solid var(--line-2);border-radius:4px;background:var(--raised)}
:where([data-prose-body]) :where(li > input[type=checkbox]:checked){border-color:var(--fg);background:var(--fg)}
:where([data-prose-body]) :where(li > input[type=checkbox]:checked)::after{content:"";display:block;width:100%;height:100%;background:var(--frame);-webkit-mask:${TICK} center/75% no-repeat;mask:${TICK} center/75% no-repeat}
:where([data-prose-body]) :where(dt){color:var(--fg);font-weight:500;margin-top:var(--p-flow)}
:where([data-prose-body]) :where(dd){margin:.2em 0 0}

:where([data-prose-body]) :where(blockquote){padding-left:1em;border-left:2px solid var(--line-2);color:var(--fg-2)}
:where([data-prose-body]) :where(hr){border:0;border-top:1px solid var(--line);margin:2.2em 0}

:where([data-prose-body]) :where(code,kbd,samp){font-family:var(--font-mono);font-size:.86em;font-variant-ligatures:none}
:where([data-prose-body]) :where(:not(pre) > code){color:var(--fg);padding:.12em .36em;border:1px solid var(--line);border-radius:5px;background:var(--raised);overflow-wrap:anywhere;box-decoration-break:clone;-webkit-box-decoration-break:clone}
:where([data-prose-body]) :where(kbd){display:inline-block;min-width:1.6em;padding:.05em .4em;text-align:center;color:var(--fg-2);border:1px solid var(--line-2);border-bottom-width:2px;border-radius:5px;background:var(--raised);line-height:1.4}
:where([data-prose-body]) :where(pre){position:relative;overflow-x:auto;padding:.95em 1.1em;border:1px solid var(--line);border-radius:12px;background:var(--raised);color:var(--fg);font-family:var(--font-mono);font-size:var(--p-code);line-height:1.65;tab-size:2;scrollbar-width:thin;overscroll-behavior-x:contain}
:where([data-prose-body]) :where(pre):focus-visible{outline:1px solid var(--fg-3);outline-offset:2px}
:where([data-prose-body]) :where(pre code){font-size:inherit;color:inherit;background:none;border:0;padding:0;white-space:pre}
:where([data-prose-body]) :where(pre[data-language])::before{content:attr(data-language);position:absolute;top:.55em;right:.8em;font-size:10.5px;letter-spacing:.08em;text-transform:uppercase;color:var(--fg-4);transition:opacity .12s ease-out;pointer-events:none}
:where([data-prose-body]) :where(pre[data-prose-active])::before{opacity:0}

:where([data-prose-body]) :where(table){display:block;overflow-x:auto;width:max-content;max-width:100%;border:1px solid var(--line);border-radius:10px;border-spacing:0;border-collapse:separate;font-size:.9em;line-height:1.5;scrollbar-width:thin}
:where([data-prose-body]) :where(th,td){padding:.55em .9em;text-align:left;vertical-align:top;border-bottom:1px solid var(--line)}
:where([data-prose-body]) :where(th){color:var(--fg);font-weight:500;background:var(--raised);white-space:nowrap}
:where([data-prose-body]) :where(tr:last-child > td){border-bottom:0}
:where([data-prose-body]) :where(th[align=right],td[align=right]){text-align:right;font-variant-numeric:tabular-nums}
:where([data-prose-body]) :where(th[align=center],td[align=center]){text-align:center}
:where([data-prose-body]) :where(td code){overflow-wrap:normal}

:where([data-prose-body]) :where(img,video){display:block;max-width:100%;height:auto;border-radius:10px;outline:1px solid var(--line);outline-offset:-1px;transition:opacity .32s var(--ease-out-expo),scale .5s var(--ease-out-expo)}
:where([data-prose-body][data-enhanced]) :where(img[data-state=loading]){opacity:0;scale:1.015}
:where([data-prose-body]) :where(img[data-state=error]){min-height:6em;background:var(--raised);color:var(--fg-3);font-size:.86em}
:where([data-prose-body]) :where(figure > img,figure > video){margin:0 auto}
:where([data-prose-body]) :where(figure){margin-top:calc(var(--p-flow) * 1.6)}
:where([data-prose-body]) :where(figure) + *{margin-top:calc(var(--p-flow) * 1.6)}
:where([data-prose-body]) :where(figcaption){margin-top:.75em;font-size:.84em;line-height:1.5;color:var(--fg-3);text-align:center;text-wrap:balance}

:where([data-prose-body]) :where(details){border:1px solid var(--line);border-radius:10px;padding:.55em .9em;interpolate-size:allow-keywords}
:where([data-prose-body]) :where(summary){display:flex;align-items:center;gap:.45em;cursor:pointer;color:var(--fg);font-weight:500;list-style:none;border-radius:4px}
:where([data-prose-body]) :where(summary)::-webkit-details-marker{display:none}
:where([data-prose-body]) :where(summary)::before{content:"";flex:none;width:.9em;height:.9em;background:var(--fg-3);-webkit-mask:${CHEVRON} center/contain no-repeat;mask:${CHEVRON} center/contain no-repeat;transition:rotate .2s var(--ease-out-expo)}
:where([data-prose-body]) :where(details[open] > summary)::before{rotate:90deg}
:where([data-prose-body]) :where(summary):focus-visible{outline:1px solid var(--fg-3);outline-offset:2px}
:where([data-prose-body]) :where(details)::details-content{block-size:0;overflow:clip;transition:block-size .24s var(--ease-in-out-quart),content-visibility .24s allow-discrete}
:where([data-prose-body]) :where(details[open])::details-content{block-size:auto}
:where([data-prose-body]) :where(details[open] > summary + *){margin-top:.6em}

@media (prefers-reduced-motion: reduce){:where([data-prose-body][data-enhanced]) :where(img[data-state=loading]){scale:1}}
`;

/* -------------------------------------------------------------------------------------------------
 * Enhancements: things HTML can't say on its own, applied to whatever is rendered inside,
 * including content that streams in later. Only attributes are set, never structure, so
 * React-rendered children are never fought over.
 * -----------------------------------------------------------------------------------------------*/

const slugify = (s: string) =>
  s
    .toLowerCase()
    .normalize("NFKD")
    .replace(/[̀-ͯ]/g, "")
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-|-$/g, "") || "section";

function enhance(root: HTMLElement, autoIds: boolean) {
  if (autoIds) {
    for (const h of root.querySelectorAll<HTMLElement>("h2:not([id]),h3:not([id]),h4:not([id])")) {
      const base = slugify(h.textContent ?? "");
      let id = base;
      for (let n = 2; document.getElementById(id); n++) id = `${base}-${n}`;
      h.id = id;
    }
  }
  // A scrollable region has to be reachable by keyboard, or its overflow can't be scrolled.
  for (const pre of root.querySelectorAll<HTMLElement>("pre:not([tabindex])")) pre.tabIndex = 0;
  // display:block (for horizontal scroll) drops table semantics in some browsers; say them out loud.
  for (const table of root.querySelectorAll<HTMLElement>("table:not([role])")) {
    table.setAttribute("role", "table");
    for (const g of table.querySelectorAll("thead,tbody,tfoot")) g.setAttribute("role", "rowgroup");
    for (const tr of table.querySelectorAll("tr")) tr.setAttribute("role", "row");
    for (const th of table.querySelectorAll("th")) th.setAttribute("role", th.getAttribute("scope") === "row" ? "rowheader" : "columnheader");
    for (const td of table.querySelectorAll("td")) td.setAttribute("role", "cell");
    if (table.scrollWidth > table.clientWidth) table.tabIndex = 0;
  }
  for (const img of root.querySelectorAll<HTMLImageElement>("img:not([data-state])")) {
    if (img.complete) {
      img.dataset.state = img.naturalWidth ? "loaded" : "error";
      continue;
    }
    img.dataset.state = "loading";
    img.addEventListener("load", () => (img.dataset.state = "loaded"), { once: true });
    img.addEventListener("error", () => (img.dataset.state = "error"), { once: true });
  }
}

/* -------------------------------------------------------------------------------------------------
 * Floating controls
 * -----------------------------------------------------------------------------------------------*/

type AnchorTarget = { id: string; label: string; x: number; y: number };
type CodeTarget = { el: HTMLElement; top: number; right: number };

const HEADINGS = "h2[id],h3[id],h4[id]";

// Where a heading's text actually ends (its last line), relative to the container: the link sits there.
function anchorFor(h: HTMLElement, box: DOMRect): AnchorTarget {
  const range = document.createRange();
  range.selectNodeContents(h);
  const rects = range.getClientRects();
  const last = rects[rects.length - 1] ?? h.getBoundingClientRect();
  return { id: h.id, label: h.textContent?.trim() ?? "", x: last.right - box.left + 6, y: last.top + last.height / 2 - box.top };
}

function codeFor(pre: HTMLElement, box: DOMRect): CodeTarget {
  const r = pre.getBoundingClientRect();
  return { el: pre, top: r.top - box.top + 6, right: box.right - r.right + 6 };
}

/* -------------------------------------------------------------------------------------------------
 * Prose
 * -----------------------------------------------------------------------------------------------*/

export type ProseProps = Omit<React.ComponentProps<"div">, "dangerouslySetInnerHTML"> & {
  /** "sm" for comments and descriptions in product UI, "md" for docs, "lg" for long reads. */
  size?: "sm" | "md" | "lg";
  /** Rendered HTML (from markdown or a CMS). Sanitize it first. Or pass children instead. */
  html?: string;
  /** Cap the line length at about 68 characters. */
  measure?: boolean;
  /** A copy-link button beside h2–h4 on hover. */
  anchors?: boolean;
  /** A copy button on code blocks, and ⌘C / Ctrl+C on a focused block copies all of it. */
  copyCode?: boolean;
  /** Give h2–h4 without an id one from their text, so they can be linked to. */
  autoIds?: boolean;
};

/** Typography for rendered rich text: rhythm, headings, lists, code, quotes, tables and figures, in tokens. */
export function Prose({
  size = "md",
  html,
  measure = true,
  anchors = true,
  copyCode = true,
  autoIds = true,
  className,
  children,
  onPointerOver,
  onPointerLeave,
  onFocus,
  onKeyDown,
  ...rest
}: ProseProps) {
  const root = useRef<HTMLDivElement>(null);
  const body = useRef<HTMLDivElement>(null);
  const copyRef = useRef<HTMLButtonElement>(null);
  const [anchor, setAnchor] = useState<AnchorTarget | null>(null);
  const [code, setCode] = useState<CodeTarget | null>(null);
  const reduce = useReducedMotion();
  const hideTimer = useRef<number>(undefined);

  useEffect(() => {
    const el = body.current;
    if (!el) return;
    enhance(el, autoIds);
    el.dataset.enhanced = "";
    let frame = 0;
    // Content that arrives later (streamed replies, lazy sections) gets the same treatment.
    const mo = new MutationObserver(() => {
      cancelAnimationFrame(frame);
      frame = requestAnimationFrame(() => enhance(el, autoIds));
    });
    mo.observe(el, { childList: true, subtree: true });
    return () => {
      mo.disconnect();
      cancelAnimationFrame(frame);
      window.clearTimeout(hideTimer.current);
    };
  }, [html, autoIds]);

  // The code button marks its block, so the block's language label can step aside for it.
  useEffect(() => {
    if (!code) return;
    code.el.setAttribute("data-prose-active", "");
    return () => code.el.removeAttribute("data-prose-active");
  }, [code]);

  const show = useCallback(
    (target: EventTarget | null) => {
      const box = root.current?.getBoundingClientRect();
      if (!box || !(target instanceof Element) || !body.current?.contains(target)) return;
      window.clearTimeout(hideTimer.current);
      const h = anchors ? target.closest<HTMLElement>(HEADINGS) : null;
      const pre = copyCode ? target.closest<HTMLElement>("pre") : null;
      setAnchor((a) => (h ? (a?.id === h.id ? a : anchorFor(h, box)) : null));
      setCode((c) => (pre ? (c?.el === pre ? c : codeFor(pre, box)) : null));
    },
    [anchors, copyCode],
  );

  // Leaving a heading or block hides its control after a beat, so the pointer can travel onto it.
  const hideSoon = () => {
    window.clearTimeout(hideTimer.current);
    hideTimer.current = window.setTimeout(() => {
      setAnchor(null);
      setCode(null);
    }, 160);
  };
  const hold = () => window.clearTimeout(hideTimer.current);

  const bodyProps = html !== undefined ? { dangerouslySetInnerHTML: { __html: html } } : { children };
  const pop = reduce
    ? { initial: { opacity: 0 }, animate: { opacity: 1 }, exit: { opacity: 0 } }
    : { initial: { opacity: 0, scale: 0.9 }, animate: { opacity: 1, scale: 1 }, exit: { opacity: 0, scale: 0.95, transition: { duration: 0.1 } } };

  return (
    <>
      <style href="stealth-ui-prose" precedence="default">
        {CSS}
      </style>
      <div
        ref={root}
        data-prose=""
        data-size={size}
        data-measure={measure || undefined}
        className={className}
        onPointerOver={(e) => {
          onPointerOver?.(e);
          if ((e.target as Element).closest?.("[data-prose-control]")) return hold();
          const inside = (e.target as Element).closest?.(`${HEADINGS},pre`);
          if (inside) show(e.target);
          else hideSoon();
        }}
        onPointerLeave={(e) => {
          onPointerLeave?.(e);
          hideSoon();
        }}
        onFocus={(e) => {
          onFocus?.(e);
          // A focused code block shows its copy button, so keyboard users see what ⌘C will do.
          if (e.target instanceof HTMLElement && e.target.matches("pre")) show(e.target);
        }}
        onKeyDown={(e) => {
          onKeyDown?.(e);
          const pre = e.target instanceof HTMLElement && e.target.matches("pre") ? e.target : null;
          if (!pre || !copyCode || !(e.metaKey || e.ctrlKey) || e.key.toLowerCase() !== "c") return;
          // With nothing selected, copy the whole block, the way the button would.
          if (window.getSelection()?.toString()) return;
          e.preventDefault();
          show(pre);
          requestAnimationFrame(() => copyRef.current?.click());
        }}
        {...rest}
      >
        <div ref={body} data-prose-body="" {...bodyProps} />

        <AnimatePresence>
          {anchor && (
            <motion.span
              key="anchor"
              data-prose-control=""
              {...pop}
              transition={{ duration: 0.14, ease: ease.out }}
              onPointerLeave={hideSoon}
              className="absolute z-10 -translate-y-1/2"
              style={{ left: anchor.x, top: anchor.y }}
            >
              <SectionLink id={anchor.id} label={anchor.label} />
            </motion.span>
          )}
          {code && (
            <motion.span
              key={`code`}
              data-prose-control=""
              {...pop}
              transition={{ duration: 0.14, ease: ease.out }}
              onPointerLeave={hideSoon}
              className="absolute z-10 origin-top-right"
              style={{ top: code.top, right: code.right }}
            >
              <CopyButton
                ref={copyRef}
                iconOnly
                size="sm"
                label="Copy code"
                copiedLabel="Code copied"
                failedLabel="Couldn’t copy"
                // Mouse users have the button; keyboard users copy the focused block with ⌘C.
                tabIndex={-1}
                aria-keyshortcuts="Meta+C Control+C"
                value={() => (code.el.querySelector("code") ?? code.el).textContent?.replace(/\n$/, "") ?? ""}
              />
            </motion.span>
          )}
        </AnimatePresence>
      </div>
    </>
  );
}

// Copies a link to the section. The page doesn't move: sharing is what people want from it.
function SectionLink({ id, label }: { id: string; label: string }) {
  const { state, copy } = useCopy({ timeout: 1400 });
  const reduce = useReducedMotion();
  const done = state === "copied";
  return (
    <>
      <button
        type="button"
        tabIndex={-1}
        aria-label={`Copy link to “${label}”`}
        onClick={() => copy(() => `${location.origin}${location.pathname}${location.search}#${id}`)}
        className={cn(
          "relative grid size-6 place-items-center rounded-md text-fg-4 outline-none",
          "before:absolute before:-inset-2.5 before:content-[''] pointer-fine:before:hidden",
          "transition-[background-color,color,scale] duration-150 hover:bg-hover hover:text-fg-2 active:scale-[0.9] active:duration-75",
          done && "text-fg-2",
        )}
      >
        <AnimatePresence initial={false} mode="popLayout">
          <motion.span
            key={done ? "done" : "link"}
            initial={reduce ? { opacity: 0 } : { opacity: 0, scale: 0.5, filter: "blur(2px)" }}
            animate={{ opacity: 1, scale: 1, filter: "blur(0px)" }}
            exit={reduce ? { opacity: 0 } : { opacity: 0, scale: 0.5, filter: "blur(2px)" }}
            transition={{ duration: 0.16, ease: ease.out }}
            className="grid place-items-center"
          >
            {done ? <Check size={14} /> : <LinkIcon size={14} />}
          </motion.span>
        </AnimatePresence>
      </button>
      <span role="status" aria-live="polite" className="sr-only">
        {done ? "Link copied" : state === "failed" ? "Couldn’t copy the link" : ""}
      </span>
    </>
  );
}

05Props

PropTypeDefaultDescription
childrenReactNode—Rendered content: headings, paragraphs, lists, code, quotes, tables, figures, details.
htmlstring—Rendered HTML instead of children. Sanitize it first; it's inserted as is.
size"sm" | "md" | "lg""md"13.5px for comments and descriptions in product UI, 15px for docs, 17px for long reads. The whole rhythm scales with it.
measurebooleantrueCaps line length at about 68 characters.
anchorsbooleantrueShows a copy-link button after h2–h4 headings on hover.
copyCodebooleantrueShows a copy button on code blocks on hover or focus; ⌘C / Ctrl+C on a focused block copies all of it.
autoIdsbooleantrueGives h2–h4 without an id a unique one from their text, so they can be linked to.

06Notes

Behavior

  • Every rule is wrapped in :where(), so it has zero specificity: a class you put on any element inside wins without !important. Colors, borders and fonts are tokens, including sugar-high's syntax colors, so highlighted code follows the theme.
  • The flow space, heading steps, code size and line height are one set of custom properties per size, so switching size rescales the whole page in proportion.
  • Content that arrives later (a streamed reply, a lazy section) is watched and gets the same treatment: ids, focusable code blocks, table roles and image fades. Only attributes are ever set, never structure, so React-rendered children aren't disturbed.
  • Wide tables and long code lines scroll inside their own box instead of widening the page; images keep their aspect from width and height, and a failed image keeps a quiet placeholder with its alt text.

Motion

  • Section links and the code copy button fade and scale in from 90% over 140ms, and linger for 160ms after the pointer leaves, so you can travel onto them. The link icon swaps to a tick with a 2px blur that clears.
  • Images fade in over 320ms and settle from 101.5% scale over 500ms on the expo ease-out; details chevrons turn 90° in 200ms, and the body opens by height over 240ms where the browser supports it.
  • External links' arrows nudge 1px up and right on hover. Reduced motion keeps the fades and drops the scale and nudges.

Accessibility

  • Code blocks and overflowing tables are focusable, because a scroll region has to be reachable by keyboard. A focused block shows its copy button, and ⌘C / Ctrl+C with nothing selected copies it, announced by a live region.
  • Tables scroll horizontally with display: block, so their table, row and cell roles are set explicitly to keep them readable to screen readers.
  • Section links are a pointer convenience, so they stay out of the tab order; headings get ids, so a table of contents or keyboard navigation can reach them. Copying a link is announced.
  • Links that open a new tab get an arrow, and headings keep scroll-margin so anchors land below a sticky header.