SaaS & Engineering

API (Application Programming Interface)

Standard way for one application to communicate with another — the foundation of modern SaaS integrations.

APIs let one software talk to another in a structured way. RESTful APIs (HTTP-based, JSON-formatted) dominate modern SaaS. Authentication via API keys, OAuth 2.0, or JWT tokens.

For Indian SMBs, APIs enable: WhatsApp Business → CRM, Razorpay → bookings, Tally → ecom, Calendly → CRM. Without APIs, every integration is manual data entry.

APIs are typically priced per call (per 1K calls) or as part of a SaaS plan. Rate limits prevent abuse. Webhooks (the inverse of API calls — server pushes data to you) are increasingly common.

India context

Indian SaaS adoption hinges on API ecosystem. Founders pick tools that have APIs over those that don't, even if features are inferior — APIs allow customization. Tools without APIs become trapped silos that stop growing.

Examples

  • A salon booking system uses WhatsApp API to send confirmations + Calendar API to block slots.
  • A D2C ecom uses Razorpay API to charge + Shiprocket API to ship + WhatsApp API to update.

FAQ

What's the difference between API and webhook?

API: you call them. Webhook: they call you. APIs are pull-based; webhooks are push-based. Modern integrations use both.

Are APIs always paid?

Most SaaS provide APIs as part of paid plans. Some are free up to a usage threshold. A few charge per call.

What's an API key vs OAuth?

API key: simple, like a password. OAuth: scoped, refreshable, more secure for user-permissioned access. OAuth standard for user-data flows.

Related concepts

webhookRESTOAuthJWTrate limitSDK

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Related glossary entries

Webhook — Mechanism where one app pushes real-time event data to another via HTTP POST — the inverse of an API call.OAuth 2.0 — Industry-standard protocol for delegated access — lets users grant apps limited access to their data without sharing passwords.JWT (JSON Web Token) — Compact, self-contained way to securely transmit information between parties as a JSON object — used widely in SaaS authentication.SDK (Software Development Kit) — Pre-packaged tools, libraries, code samples, and documentation that helps developers integrate with a specific platform.

More in SaaS & Engineering

WebhookOAuth 2.0JWT (JSON Web Token)SDK (Software Development Kit)Shopify (India)
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