API Overview | Close | Developer API Documentation

Base URL: https://api.close.com/api/v1

Close uses industry-standard REST conventions with predictable URL structures, standard HTTP methods, and JSON request/response bodies.

Authentication

All API requests require authentication. Two methods are supported:

API Keys — Best for scripts, internal tools, and server-side integrations. Use HTTP Basic Auth with your API key as the username and an empty password.
OAuth 2.0 — Best for user-facing integrations.

Concept	Description
Leads	Companies or organizations — the primary object in Close. Contain contacts, tasks, opportunities, and activities.
Contacts	Individual people within a lead.
Opportunities	Potential deals tracked through pipeline stages.
Activities	Calls, emails, notes, SMS, meetings, and other interactions logged on leads.
Custom Fields	Store arbitrary data on leads, contacts, opportunities, and custom activities.

All requests use JSON (Content-Type: application/json).
PUT requests behave as patches — send only the fields you want to update. See Fields.
List endpoints support pagination via _skip/_limit or cursor-based pagination.
Use the _fields parameter to control which fields are returned and improve performance.
Rate limits apply to all endpoints. Handle 429 responses with exponential backoff.

Webhooks — Subscribe to events and receive POST notifications when data changes.
Event Log — Query the last 30 days of changes to any object.

Code	Meaning
`200`	Success
`201`	Created (newer endpoints)
`400`	Bad request — check your parameters
`401`	Unauthorized — invalid or missing credentials
`404`	Not found
`429`	Rate limited — back off and retry

See HTTP Response Codes for the full list.

Note: This spec is currently considered experimental and does not contain 100% coverage of request/response schemas.