HubSpot

HubSpot API provides comprehensive access to CRM, marketing, sales, and service hub features.

OAuth 2.0 is the primary authentication method with private app tokens also available. The API offers excellent documentation with interactive API explorer and Postman collections.

Rate limits are 100 requests per 10 seconds for OAuth apps. Official SDKs available for Python, Node.js, Ruby, and PHP. Supports webhooks for real-time updates and has over 30,000 integrations.

Ideal for marketing automation, CRM integration, and building custom business solutions. Free tier available with generous limits.