create and manage subscribers via the Kit (formerly ConvertKit) v4 API
domain: developers.kit.com · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
POST email_address (and optional first_name, fields) to https://api.kit.com/v4/subscribers — this upserts by email, updating first_name if the subscriber already exists
Authenticate with either an X-Kit-Api-Key header (personal/server use) or an OAuth2 bearer token (applications)
Reference custom fields by their field key (not display label) inside the fields object, or the call returns 422
List subscribers with GET /v4/subscribers, using created_after/created_before/updated_after/updated_before filters (v3's from/to/updated_from/updated_to no longer exist)
Unsubscribe via POST /v4/subscribers/:id/unsubscribe (by id only — look up the id via ?email_address= first if you only have an email)
Known gotchas
v4 dropped page/offset pagination entirely in favor of cursor-based before/after params
v4 API keys are not compatible with v3 endpoints and vice versa
Passing an unrecognized custom field key returns a 422 rather than silently ignoring it
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