---
title: "Add an mTLS certificate authority"
canonical: "https://bird.com/docs/api/reference/create-workspace-mtls-certificate-authority"
---

# Add an mTLS certificate authority

`POST /v1/workspace/mtls-certificate-authorities`

Adds a certificate authority that issues client certificates for your workspace. The mTLS endpoint accepts a client certificate that chains to one of these certificate authorities. Your quota sets how many certificate authorities a workspace can have, at most two, so you can add a new one before you remove the old one. Adding one past the quota, or one that is already registered, returns 409. The certificate authority must issue certificates only to you. If it also issues them to others, set `expected_san` in the mTLS settings. If mTLS is not enabled for this workspace, this returns 422.

## Servers

- `https://{region}.platform.bird.com`: Regional API endpoint. Use the host for the region your organization is hosted in. Official Bird SDKs and the CLI select it automatically from your API key, so you rarely need to set it by hand.
  - `region`: `us1`, `eu1`. Default: `us1`. The region your organization's data is hosted in.
- `https://platform.bird.com`: Region-independent endpoint for authentication and account administration.
- `http://localhost:8080`: Local development.

## Authentication

Use one authentication option:

- `BearerAuth`: HTTP bearer authentication. Pass the API key as a bearer token in the `Authorization` header. Workspace
keys use `bk_{region}_*`; organization master keys use `bm_{region}_*`.
The prefix identifies the region and selects the
API endpoint. Official Bird SDKs and the CLI derive the region from the key.

- `CookieAuth`: Send `bird_session` in cookie. Session cookie set after signing in to the Bird dashboard. The cookie
value is an opaque session token; no session data is stored in the cookie
itself.

## Code samples

**cURL**

```sh
curl -X POST "https://us1.platform.bird.com/v1/workspace/mtls-certificate-authorities" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "certificate": "-----BEGIN CERTIFICATE-----\nMIIB...\n-----END CERTIFICATE-----\n"
  }'
```

Examples: [cURL](/docs/api/reference/create-workspace-mtls-certificate-authority.curl.md)

## Example response `201`

```json
{
  "id": "mtlsca_01krdgeqcxet5s7t44vh8rt9mg",
  "subject": "CN=Example Client CA,O=Example Inc.",
  "fingerprint_sha256": "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08"
}
```

## Header parameters

- `Idempotency-Key` (string, optional)

  Client-supplied key. On operations supporting request deduplication, a retained
  response is replayed for duplicate requests with the same key within the
  idempotency window (3 hours by default). This protection requires a workspace,
  organization, or staff-account scope. User-only and unscoped unauthenticated operations,
  streams, and operations with a separate replay contract do not use this
  response replay.

  On a supported operation, if idempotency protection is unavailable before execution, the API returns
  `503 IdempotencyUnavailable` (E01033) without executing this attempt. Retry with
  backoff using the same key and request. An operation that takes effect before
  its response is retained can still execute again on retry.

  Two distinct 409 errors signal misuse:

  - `request_in_progress` (E01004): The same key is currently being
    processed by a concurrent request. Wait briefly and retry. The lock expires within 30 seconds.
  - `idempotency_key_reuse` (E01005): The same key has already completed
    against a different request body or method. Generate a new key.

  Recommended key format is `<event-type>/<entity-id>` (for example `welcome-user/usr_abc123`).
- `X-Workspace-Id` (string, optional): Workspace context for the request. Required for dashboard authentication and master keys. Workspace keys and access tokens already identify their workspace; send that workspace or omit the header. A different one is rejected.
- `X-Organization-Id` (string, optional): Organization context for the request. Required for dashboard authentication. An API key or access token carries its own organization, so send either that organization or no header at all; a different one is rejected.

## Request body

- `certificate` (string, required): One PEM-encoded X.509 certificate.

## Response body

- `id` (string, required)
- `subject` (string, required): The distinguished name of the certificate authority.
- `fingerprint_sha256` (string, required): The SHA-256 fingerprint of the certificate, in lowercase hexadecimal.
- `not_before` (string, required): Start of the validity period of the certificate authority.
- `not_after` (string, required): End of the validity period of the certificate authority.
- `created_at` (string, required): When you added the certificate authority.

## Related resources

- [Should I use a Bird SDK or call the API directly?](/explained/platform/should-i-use-an-sdk-or-call-the-api-directly) (answer)
- [Build your first integration](/learn/paths/integration) (course)
- [Send your first email](/docs/get-started/send-your-first-email) (docs)

[Get an implementation brief](/learn/workspace?topic=api-basics)