How to implement a paywall for blog posts in Sanity CMS?

You're on the right track! Your approach is actually a solid and common pattern for implementing paywalled content. Let me break down the recommended way to do this:

The Basic Approach (What You Described)

Yes, adding a boolean field to your blog post schema is exactly the right starting point:

{
  name: 'isPremium',
  title: 'Premium Content',
  type: 'boolean',
  description: 'Check this to put content behind paywall'
}

Then in your website code (like Next.js), you'd:

1. Check if the user is authenticated and has an active subscription (using something like NextAuth.js + Stripe)
2. Query the post and check the isPremium field
3. Show full content to paid users, or just a preview/excerpt to free users

Making It Better: Content Preview Strategy

Instead of just hiding everything, consider these improvements:

Add an excerpt field to your schema so free users can see a teaser:

{
  name: 'excerpt',
  title: 'Preview Excerpt',
  type: 'text',
  description: 'Short preview shown to non-subscribers'
}

Use GROQ to conditionally fetch content in your Next.js getServerSideProps or Server Components:

// In your Next.js page
const query = `*[_type == "post" && slug.current == $slug][0]{
  title,
  excerpt,
  isPremium,
  ${userIsPaid ? 'content' : ''}
}`

This way, you're not even sending the full content to the client if the user isn't paid.

The Authentication Side

For the authentication/subscription checking part, you'd typically:

1. Use an auth provider like NextAuth.js or Clerk to handle user authentication
2. Use Stripe (or similar) for subscription management
3. Check subscription status in your Next.js middleware or getServerSideProps/Server Components before rendering the page

Important Security Note

Make sure the authentication check happens server-side (in Next.js Server Components, getServerSideProps, or API routes), not just in client-side JavaScript. Otherwise, someone could inspect the page source or network requests and access the premium content anyway.

Starter Resources

While Sanity doesn't have a specific paywall starter, you can combine:

• Any Sanity + Next.js starter
• Stripe subscription examples from Vercel
• Authentication with NextAuth.js or Clerk

Your approach is fundamentally correct - Sanity handles the content modeling (with the boolean flag), and your frontend application handles the authentication and conditional rendering. Keep it simple to start, and you can always add more sophisticated features later!