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

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01

Understand the problem

Purging cached data/routes when content changes.

nextjsrevalidationrevalidatetagcaching
02

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03

Study the solution

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.

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04

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
}
05

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