Fix: Supabase Realtime Subscription Not Receiving Updates

You’ve followed the tutorials, you’ve initialized your Supabase client, and you’ve written the perfect channel.subscribe() block. You open your app, change a value in the database, and... nothing. No toast notification, no state update, no console log. The stream is silent.

This is the "Publication Toggle Trap."

Supabase Realtime feels like magic—it allows you to turn your database into a live data feed with just a few lines of code. But unlike standard SQL queries, Realtime is an "opt-in" feature. For "Vibe Coders" using AI assistants to build their features, this is a top-tier frustration. AI tools can write the code for the subscription, but they cannot click the button in your Supabase Dashboard to turn the engine on.

In this guide, we’ll explain how Supabase Realtime works under the hood, identify the #1 missed step that kills subscriptions, and provide the diagnostic checklist to get your live updates flowing.

How Supabase Realtime Works: WebSockets + Replication

To fix the silence, you have to understand the path the data takes.

When a change happens in your Postgres database, it is recorded in the WAL (Write Ahead Log). Supabase runs a specialized service called Realtime that "listens" to this log.

If a table is part of the supabase_realtime Publication, the Realtime service captures the change, converts it into a JSON message, and broadcasts it over a WebSocket connection to your connected users.

If any part of this chain—the Publication, the WebSocket, or the Security Layer—is broken, the update will never reach your app.

The #1 Missed Step: Enabling the Publication

By default, Realtime is disabled for all tables. This is a security and performance feature to prevent your database from broadcasting every single update to the world.

How to fix it:

1. Go to your Supabase Dashboard.
2. Navigate to Database > Publications.
3. Click on the supabase_realtime row (or create it if it’s missing).
4. Click Edit.
5. Check the box for your specific table (e.g., messages or orders).
6. Click Save.

Pro Tip: If you are using the SQL Editor, you can run this command:

alter publication supabase_realtime add table your_table_name;

Common Trigger 1: RLS Policies Blocking Realtime Events

Supabase Realtime respects your Row Level Security (RLS) policies. If a user doesn't have permission to SELECT a row, they won't receive Realtime updates for that row.

The Fix: Ensure your RLS policy allows the authenticated role to see the data. If you are testing as an anonymous user, ensure your anon policy is correctly configured. For a deep dive on fixing RLS bugs, see our Supabase RLS guide.

Common Trigger 2: Client-Side Subscription Lifecycle Bugs

AI-generated code often misses the "Cleanup" phase of a subscription. If you are using React, you must ensure you are unsubscribing when the component unmounts. If you don't, you’ll end up with "Zombie Subscriptions" that fight over the WebSocket connection.

The Success Pattern:

useEffect(() => {
  const channel = supabase
    .channel('room1')
    .on('postgres_changes', { event: 'INSERT', schema: 'public', table: 'messages' }, payload => {
      console.log('New message!', payload)
    })
    .subscribe()

  return () => {
    // ⚠️ IMPORTANT: Clean up!
    supabase.removeChannel(channel)
  }
}, [])

Common Trigger 3: Missing Primary Keys

Supabase Realtime (specifically for UPDATE and DELETE events) requires each table to have a Primary Key.

Why? Because to tell the client "This row was updated," the system needs a stable ID to identify which row it’s talking about. If your table doesn't have an id or uuid primary key, INSERT might work, but UPDATE events will be silently ignored.

Debugging: Using the Dashboard Inspector

If you aren't receiving updates, the Supabase Dashboard has a hidden gem: the Realtime Inspector.

1. Go to your Dashboard.
2. Navigate to Realtime > Inspector.
3. Choose your table and click Listen.
4. Perform an action in your database.

• If the Dashboard sees the update but your app doesn't: The issue is in your frontend code or your WebSocket connection.
• If the Dashboard DOES NOT see the update: The issue is in your Publication settings or database-level replication.

FlowQL: Building Scalable Realtime Systems

Building a "Chat" app is the "Hello World" of Realtime. Building a production system where thousands of users receive live updates, notifications, and synchronized state is the "last 20%" of backend engineering. AI assistants are great at the syntax, but they are blind to the Replication Lag, Event Ordering, and Connection Management required for high-scale apps.

At FlowQL, we help companies scale their Supabase Realtime infrastructure. We provide the senior technical oversight to optimize your publications, secure your WebSocket channels, and ensure your "Vibe" stays live under heavy load.

If your "Live" features are consistently lagging or failing, it's time for a professional backend audit.

Conclusion

Supabase Realtime fails primarily because of missing Publications or RLS restrictions. By explicitly enabling your tables for replication and following proper subscription lifecycle patterns, you can build apps that feel instant and alive.

Your Action Plan:

1. Enable the supabase_realtime publication for your table.
2. Verify your table has a Primary Key.
3. Check that RLS isn't blocking the SELECT for your users.
4. Implement the useEffect cleanup pattern in your frontend.

Don't let a silent stream kill your UX. [Book a session with FlowQL] and let’s get your Supabase Realtime flowing perfectly.

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FAQ: Supabase Realtime Troubleshooting

Q: Can I subscribe to multiple tables in one channel? A: Yes, you can chain multiple .on() methods before calling .subscribe(). However, for large apps, it's often better to separate concerns into different channels.

Q: Does Realtime work with Prisma? A: Yes. Realtime listens to the database-level WAL, so it doesn't matter if you use Prisma, Drizzle, or the Supabase SDK to change the data.

Q: Why do I only see 'INSERT' events but not 'UPDATE'? A: This usually means your table is missing a Primary Key, or you haven't enabled "Full" replica identity in your Postgres settings.