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.

Connectors extend Power Automate and Power Apps to any API, usually authenticated through an Entra app registration and governed by DLP policies; the Graph-backed ones follow Graph API basics.

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.