Key takeaways
- An API lets software systems talk to each other; a REST API does it over HTTP using URLs and standard methods (GET, POST, PUT, DELETE).
- APIs power integrations: payment gateways, WhatsApp messages, CRMs, mobile apps and dashboards.
- For business owners, understanding APIs helps scope integrations and evaluate software.
When your website sends an order to a shipping company, adds a lead to your CRM, or a mobile app loads your products, an API is doing the work. You don’t need to code to understand them — and understanding them makes you better at planning digital projects.
A restaurant analogy#
You (the app) don’t walk into the kitchen (the database). You give an order to the waiter (the API) from a menu (the documentation). The waiter brings back what you asked for in a standard format. The kitchen can change how it works internally, as long as the menu stays the same.
How REST requests look#
| Method | Purpose | Example |
|---|---|---|
| GET | Read data | GET /api/products/42 |
| POST | Create | POST /api/orders with order details |
| PUT / PATCH | Update | PATCH /api/orders/105 status = shipped |
| DELETE | Remove | DELETE /api/cart/items/7 |
Responses usually come as JSON:
{
"id": 42,
"name": "Steel Almirah 4 Shelves",
"price": 18500,
"in_stock": true
}And with a status code: 200 OK, 201 Created, 400 Bad Request, 401 Unauthorized, 404 Not Found, 429 Too Many Requests, 500 Server Error — see HTTP status codes.
Authentication#
- API keys — simple secret tokens; must stay on the server.
- OAuth — users grant access without sharing passwords (e.g. “Sign in with Google”, connecting a Google Ads account).
- Session/JWT tokens — for logged-in users of your own app.
Need a hand with this?
Get a quick, honest review of your website’s SEO.
Common business integrations#
- Payments: Razorpay, Stripe, PayU.
- Messaging: WhatsApp Business Platform, SMS gateways, email services.
- CRM: Zoho, HubSpot, Salesforce.
- Shipping: Shiprocket, Delhivery.
- Accounting: Tally integrations, Zoho Books.
- Google: Search Console, Analytics, Maps, Sheets.
- AI: language model APIs for chatbots and automation (this site’s assistant can connect to one).
Webhooks: APIs in reverse#
Instead of your system asking “has the payment completed?” every minute, the payment provider sends a webhook (an HTTP POST) to your URL when it happens. Most modern integrations combine APIs and webhooks.
WordPress REST API#
WordPress includes a REST API at /wp-json/. It powers the block editor, headless front ends and mobile apps, and custom endpoints like the quick search and chatbot on this site. See Fetch API guide and headless CMS.
Questions to ask when scoping an integration#
- Does the other system have a documented API? REST, GraphQL or something older?
- What authentication does it need, and who owns the account?
- Are there rate limits or costs per call?
- Is data sync one-way or two-way? Real-time or scheduled?
- What happens when the API is down — retries, queues, alerts?
REST API FAQ#
REST vs GraphQL?#
REST uses many URLs with fixed responses; GraphQL uses one endpoint where clients request exactly the fields they need. Both are widely used.
Is an API secure?#
It can be, with HTTPS, authentication, authorisation checks, input validation and rate limiting.
Can you integrate my website with other tools?#
Yes — CRMs, payments, WhatsApp, dashboards and more. Tell me what you want connected.