Drafts, preview & webhooks

When an editor changes a published document, Sanity doesn't touch the published version. It writes a sibling document whose _id is the published id with a drafts. prefix: post-123 keeps serving production while drafts.post-123 accumulates edits. Publishing copies the draft over the published document and deletes the draft; unpublished work exists only as a drafts.* document.

Which of the pair a query sees is the perspective:

• perspective: 'published' — published documents only. Production traffic.
• perspective: 'drafts' — each draft overlays its published twin, and unpublished drafts appear too. Exactly what an editor expects preview to show.

export const previewClient = client.withConfig({
  perspective: 'drafts',
  useCdn: false,
  token: process.env.SANITY_VIEWER_TOKEN, // drafts require auth
})

Preview mode

Sanity's Presentation tool embeds your site next to the Studio: editors click into the page, edit fields, and watch the live site update before publishing. Under the hood it's Next.js draft mode — a route enables draftMode(), and your data layer switches client:

import {draftMode} from 'next/headers'

const {isEnabled} = await draftMode()
const data = await (isEnabled ? previewClient : client).fetch(query, params)

Webhooks close the loop

Lesson 3 cached pages until revalidateTag fires — a GROQ-powered webhook is what fires it. In sanity.io/manage you give the webhook a filter (which documents trigger it) and a projection (what the payload contains):

// Filter: fire on publish/unpublish of posts
_type == "post"

// Projection: exactly what the revalidate route needs
{ "tag": _type, "slug": slug.current }

Your route handler verifies the signature (parseBody from next-sanity/webhook), then calls revalidateTag(body.tag). Publish → webhook → eviction → next request renders fresh. Seconds of latency, zero rebuild queue.

The challenge models the heart of all this: one content lake, two perspectives. The same query returns different worlds depending on who's asking.

Run it. 'published' ignores drafts entirely; 'drafts' overlays each draft on its published twin and includes never-published drafts. Try 'publishing' p2 by copying its draft into a published doc.

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That's the course: content modeled in code, queried with GROQ, cached and revalidated in Next.js, rendered from structured blocks, and kept honest by drafts, preview, and webhooks — a CMS pipeline you can reason about end to end.