Curated list of the leading open‑source Customer Relationship Management platforms that provide robust, well‑documented APIs (REST/JSON, GraphQL, SOAP, etc.) for seamless integration and custom development.
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A fully‑featured fork of SugarCRM offering a comprehensive REST API, extensive webhooks, and SDKs for PHP, JavaScript, and Java.
Part of the Odoo ERP suite; provides a JSON‑RPC/REST API, XML‑RPC endpoints, and an extensible ORM for Python developers.
Lightweight CRM with a modern REST API, OAuth2 authentication, and built‑in API explorer for rapid prototyping.
Feature‑rich CRM built on Vtiger; offers a fully documented REST/JSON API, batch operations, and webhook support.
Classic open‑source CRM with a robust SOAP and REST API, plus a developer portal with SDKs for PHP, Node.js, and Java.
Non‑profit focused CRM offering a REST API, JSON‑API, and extensive hooks for Drupal, Joomla, and WordPress integrations.
Modular suite with a simple REST API, enabling CRUD operations on contacts, leads, and opportunities.
Enterprise‑grade CRM featuring a powerful REST/JSON API, GraphQL endpoint, and a built‑in workflow engine for developers.
Gamified CRM platform that provides a clean REST API, OAuth2 support, and extensible service layers for custom apps.
Ruby on Rails based CRM with a minimalist REST API, JSON responses, and easy integration via Rails engines.
Low‑code CRM offering a fully documented GraphQL and REST API, role‑based access control, and webhook capabilities.
Java‑centric CRM with a comprehensive SOAP and REST API, JAX‑RS support, and OSGi modular architecture.
Open‑source ERP with a built‑in CRM; exposes a JSON‑RPC/REST API and Frappe framework hooks for deep customization.
B2B‑focused CRM delivering a robust REST API, Symfony‑based service container, and extensive data import/export tools.
All‑in‑one groupware with a CRM component; offers a REST/JSON API, WebDAV, and CalDAV support for integrated workflows.
Java‑based CRM/ERP platform featuring a clean REST API, OpenAPI spec, and a low‑code UI builder for rapid extensions.
Open‑source marketing automation with CRM capabilities; provides a REST API, webhooks, and OAuth2 for campaign integration.
Lightweight, PHP‑driven CRM offering a straightforward REST API, JSON responses, and easy plug‑in architecture.
Self‑hosted version of Bitrix24 with a well‑documented REST API, webhooks, and extensive JavaScript SDK for custom apps.
Modular CRM framework built on Laravel; offers a RESTful API, Laravel Passport OAuth2, and event‑driven extensions.