---
title: "Subscribe or unsubscribe a contact from a topic"
method: POST
path: "/api/v1/topics/{id}/subscriptions"
tags: ["Topics"]
---

# Subscribe or unsubscribe a contact from a topic

`POST /api/v1/topics/{id}/subscriptions`

## Request

- Base URL: `https://api.sendly.now`
- URL: `https://api.sendly.now/api/v1/topics/{id}/subscriptions`
- Auth: one of:
  - HTTP bearer
  - API key in cookie `better-auth.session_token`
  - OAuth 2 (authorization code, authorization URL `https://app.sendly.now/api/auth/oauth2/authorize`, token URL `https://app.sendly.now/api/auth/oauth2/token`, scopes: `topics:write`)

The two directions behave differently, and the asymmetry is deliberate: consent needs proof, withdrawal of consent does not.

`subscribed: true` does NOT subscribe anyone. It parks the contact at `pending` and returns a `confirmation_url`; nothing is mailed on this topic until somebody opens it. There is no parameter to skip that step. A caller asserting a subscription is not evidence that the mailbox holder agreed — anyone can type an address into a form — and treating the assertion as consent is the exact failure double opt-in exists to prevent. Sendly does not send the confirmation email; you do, from your own verified domain, because it is your relationship with the contact and your sending reputation.

`subscribed: false` records the opt-out immediately. Requiring somebody to confirm that they want to stop is a dark pattern, and it is also the fastest route to a spam report.

Requires the `topics:write` scope — Create and edit topics, and change what your contacts are subscribed to — this decides who your campaigns reach.

## Path parameters

- `id` string, uuid, required: Resource id.

## Request body

- TopicSubscribeV1
  - `contact_id` string, uuid, required
  - `subscribed` boolean, required: True asks to subscribe, which starts a DOUBLE OPT-IN: the contact is parked at `pending` and a confirmation link is sent. There is no way to skip that from the API — a subscription an API caller asserts is not evidence the mailbox holder agreed, and treating it as consent is exactly what double opt-in exists to stop. False records an unsubscribe, which takes effect immediately.

## Response `200`

The resulting subscription

- TopicSubscriptionV1
  - `confirmation_url` string, nullable, required: Present only when this call started a double opt-in. Sendly does NOT send the confirmation email — you do, from your own verified domain, because it is your relationship with the contact and your sending reputation. The subscription stays `pending`, and is NOT mailed, until someone opens this link.
  - `confirmed_at` string, date-time, nullable, required
  - `contact_id` string, required
  - `status` 'pending' | 'subscribed' | 'unsubscribed', required: `subscribed`: mail them about this. `unsubscribed`: do not. `pending`: a confirmation link was sent and has NOT been clicked — never treat this as consent, which is the whole point of double opt-in.
  - `topic_id` string, required

## Other responses

- `401`: `invalid_api_key` or `invalid_session` — missing or invalid credentials.
- `403`: `scope_missing`, `project_access_denied`, or `project_disabled`.
- `404`: `resource_not_found` — no topic with this id belongs to the authenticated project.
- `422`: `validation_error` — query, path, or body parameters did not match the schema.
- `429`: `rate_limited` — see `Retry-After` and the `RateLimit` headers.
- `500`: `internal_error`.

---

[API](https://skmtc.dev/sendly/apis/sendly-api.md) · [All operations](https://skmtc.dev/sendly/apis/sendly-api/llms.txt) · [OpenAPI document](https://skmtc.dev/sendly/apis/sendly-api/revisions/ce7cfb7f7c7e?raw)