An API (Application Programming Interface) is a defined interface — typically over HTTP for modern systems — that lets one software system request data or actions from another. Customer portals depend on APIs to read data from a business’s CRM (customer info), billing system (invoices), file storage (documents), product (usage data), and support platform (tickets).
Common API styles: REST (most prevalent, JSON over HTTP), GraphQL (single endpoint with flexible queries), and SOAP (legacy, XML-based). When evaluating portal platforms, check the API’s depth — can you read AND write all the data you need, or only read? Webhooks for event notifications are also key.
For portal integrations, define which system owns each field before writing code. The CRM might own contact details, the ERP owns orders and invoices, and the identity system owns login state. Without that ownership map, two-way synchronization creates conflicts and misleading portal data.
Also verify authentication, tenant scoping, pagination, rate limits, idempotency, versioning, sandbox access, and webhook retry behavior. A published API is useful only when it supports the complete customer workflow you need.