Power Platform custom connectors

Power Platform ships hundreds of pre-built connectors for Microsoft 365 services, Azure, Dynamics 365, and major third-party SaaS apps. When the system you need isn't covered, custom connectors let you wrap any REST API as a Power Platform connector — making it usable from Power Automate flows, Power Apps, and Copilot Studio agents.

What a custom connector is

A custom connector is essentially a manifest for a REST API described in OpenAPI (Swagger) format with Power Platform-specific extensions:

• Authentication — how the connector authenticates (API key, OAuth, basic auth, no auth).
• Operations — endpoints the connector exposes (Get-customer, Create-order, etc.).
• Parameters — what each operation accepts.
• Responses — what each operation returns.
• Triggers — events the connector can subscribe to (for Power Automate).

Once registered in a Power Platform environment, the connector appears in the connector list alongside built-in connectors — users select it, fill in actions, build flows or apps.

Common use cases

Wrap an in-house API

Your company has internal services exposing REST APIs. Build a custom connector and Power Platform users can call those services without writing code:

• Customer-management API.
• Internal pricing service.
• Custom workflow system.

Wrap a third-party API without a built-in connector

Many SaaS apps don't have built-in Microsoft connectors but expose REST APIs. Wrap them yourself.

Add authentication or transformation to an existing API

Sometimes the built-in connector exists but doesn't support a specific auth method or response transformation. A custom connector wraps the API with your specific requirements.

Building a custom connector

The typical flow:

1. Have a REST API with documented endpoints.
2. Provide an OpenAPI definition — or use the Power Platform connector designer to define operations manually.
3. Configure authentication — OAuth 2.0, API key, basic auth.
4. Define actions in the connector designer.
5. Define triggers (for Power Automate) if the API supports webhooks.
6. Test with the built-in test tool.
7. Share the connector with the environment's users.

Configured in the Power Platform admin centre or Power Apps maker portal → Custom connectors.

Authentication

The most-used auth types:

• OAuth 2.0 — the API supports OAuth. Configure client ID, secret, scopes; users authenticate with the API the first time they use the connector.
• API key — single key shared across the connector. Users may or may not see the key.
• Basic — username and password.
• No auth — public APIs.

OAuth is the modern norm; configure carefully.

Connection references

A connection reference is the runtime mapping of a connector to a specific account or credential. Multiple users of the connector each have their own connection reference (their own OAuth token, their own API key).

For shared / service-account scenarios, service principal authentication lets the connector authenticate as an identity rather than a user.

Premium classification

Custom connectors are premium connectors in licensing terms — users invoking a custom connector need Power Platform Premium licensing (per-user, per-app, or pay-as-you-go).

This catches some organisations off-guard: build a useful custom connector and find that scaling it to many users requires premium licences across the board.

Connector certification

Microsoft offers a connector certification process for ISVs publishing connectors to all Power Platform customers. Once certified, the connector appears in the public catalogue alongside Microsoft's first-party connectors. For internal-only connectors, certification isn't necessary.

Limitations

• Response size — connectors have response-size limits; very large API responses may need pagination.
• Latency — connector overhead adds milliseconds to API calls.
• Retry behaviour — connector retry policies apply per call.
• API rate limits — the underlying API's rate limits apply; connectors don't magically scale.

Operational considerations

• Connector ownership — assign an owner per connector.
• Documentation — describe each operation, especially edge cases.
• Version management — when the underlying API changes, update the connector definition.
• Monitor usage — see who's using which connector via the CoE Toolkit.

For organisations building meaningful Power Platform solutions on top of internal or third-party APIs, custom connectors are essential. The investment in defining the connector is one-time; the connector is then reusable across every Power App, flow, and agent in the environment.