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What is on-demand revalidation in Next.js (revalidatePath / revalidateTag)?

Q: What is on-demand revalidation in Next.js (revalidatePath / revalidateTag)?

**TL;DR.** revalidatePath(path) and revalidateTag(tag) **invalidate cached routes/data immediately** — typically called from a **Server Action or webhook** after content changes — so the next request **regenerates fresh** content instead of waiting for a time-based interval. CMS publish webhook / action revalidateTag() purge cache <path class='d-edge-accent' d='M354

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Understand the problem

Purging cached data/routes when content changes.

nextjsrevalidationrevalidatetagcaching

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Read the code

Tag data, then revalidate after a mutation

// read with a tag
await fetch('https://api/posts', { next: { tags: ['posts'] } });

// Server Action after creating a post:
'use server';
import { revalidateTag } from 'next/cache';
export async function createPost(data) {
  await db.post.create(data);
  revalidateTag('posts');          // every page using 'posts' regenerates
}

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