What Is an API and How Does It Work?

What it applies to

Websites that need to communicate with external services — CRMs, payment processors, analytics platforms, authentication systems, or any third-party data source.

How an API call works

• The browser or server sends an HTTP request to an API endpoint — a specific URL that accepts that type of request (e.g., GET /users or POST /leads).
• The request includes any required data (in the URL, headers, or request body) and an authentication token to verify the caller's identity.
• The API processes the request and returns a response — typically in JSON format — containing the requested data or a confirmation of the action taken.
• The front-end JavaScript reads the response and uses it to update the page without a full reload.

Common web integrations via API

• CRM: A contact form submits to HubSpot or Salesforce via their API, creating a new lead record automatically.
• Payment: Stripe's API processes card payments and returns a success or failure response to the checkout page.
• Authentication: Auth0 or Supabase APIs handle user login, token validation, and session management.
• Analytics: GA4 Measurement Protocol API sends server-side events that aren't captured by the browser tag.

In Webflow

Webflow's native Logic and Webhooks features allow no-code API connections. For more complex integrations, use Webflow's REST API with tools like Make or Zapier, or custom JavaScript embedded in Webflow's custom code fields.