Realtime Connected Clients, Supabase

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At a glance

The count of WebSocket clients currently subscribed to your Supabase Realtime service. This is a Supabase-distinctive signal: every connected client holds an open WebSocket and consumes a slot against your project’s concurrent-connection ceiling. It answers “how many live, persistent sessions is my project carrying right now?” Connected clients drive Realtime billing, shape the writer’s broadcast workload, and are the first thing to inspect when live features feel laggy or when you approach a plan limit. Unlike a request-rate metric, each client here is a standing cost, not a momentary one.

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Calculation

connected_clients = count(distinct websocket sessions currently open
                          to the Realtime endpoint)

• One session, one client. A client that subscribes to ten channels over a single WebSocket counts once here. That is why this card and Active Realtime Channels can move independently: a code change that splits one channel into ten multiplies channels but not clients.
• It is a level, not a flow. The number does not accumulate over the period. At any instant it is the headcount of open sockets. A busy hour with high churn (clients joining and leaving) can show a stable connected-client count even while Realtime Disconnect Rate (per min) is elevated.
• It maps directly to your concurrency ceiling. Supabase enforces a maximum concurrent Realtime connection limit per plan. This card is the live reading against that ceiling, which is why it is a Hero card: hitting the ceiling silently rejects new subscribers, and live features simply stop working for the users who could not connect.

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Worked example

1. Headroom is comfortable but shrinking. 312 of 500 is 62% utilisation. The morning shift is fully logged in; the afternoon overlap shift adds roughly 120 more consoles at 14:00, which would push the project to 432 (86%). That is close enough to warrant either a plan upgrade before a seasonal spike or a review of whether idle tabs are holding sockets unnecessarily.
2. Channels far outnumber clients, which is expected here. 1,240 channels across 312 clients is roughly four channels per client (their open tickets plus presence). If this ratio suddenly jumped to forty channels per client, that would point to a subscription leak in the front-end (channels not being cleaned up on ticket close), which inflates the writer’s broadcast fan-out without adding users.
3. The disconnect rate is benign. Four disconnects per minute at shift start is normal: agents refreshing, switching networks, reconnecting. The card to watch is the disconnect-rate sibling; a sustained spike there would mean clients are being dropped involuntarily, which connected-client count alone would not reveal because reconnects keep the headcount roughly flat.

Capacity framing:
  - Current: 312 / 500 = 62% of concurrent ceiling
  - Projected at 14:00 overlap: ~432 / 500 = 86%
  - Action trigger: sustained >85% means provision headroom now,
    because new subscribers above the ceiling are rejected silently.

1. Connected clients is a standing cost, not a momentary one. Unlike a query that finishes, each client occupies a slot for as long as the session is open. Capacity planning here is about peak concurrency, not throughput.
2. The ceiling is the real threshold. There is no fixed alert value because the meaningful limit is your plan’s concurrent-connection ceiling. Set your own sensitivity threshold in Vortex IQ at roughly 85% of that ceiling.
3. Read it with channels and disconnects, never alone. Connected-client count is stable under churn and blind to subscription leaks. The three Realtime cards together tell you whether the service is healthy, leaking, or unstable.

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Sibling cards

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Reconciling against the source

Project dashboard, then Reports, then Realtime for concurrent-connection and message charts over time. This is the authoritative managed-service view. Project dashboard, then Logs, then Realtime to inspect individual connect and disconnect events with client identifiers. Project Settings, then Billing, or your plan page to confirm the concurrent Realtime connection ceiling for your tier.

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Known limitations / FAQs

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Tracked live in Vortex IQ Nerve Centre