Introduction
Everytime your app shows you live weather, or tracks your order, it's powered by an API call. An API call is something how software applications communicate and exchange data. For instance, thinking of sending a digital request “Hey, can I take a day off” and getting a response in return.
Whether you’re syncing contacts from your CRM to a marketing tool or fetching product inventory from an e-commerce store, API calls are what makes it all happen. In this blog let's discuss how they work, why it is important, and how to use API calls wisely.
What Is an API Call?
API stands for Application Programming Interface, a set of rules that lets applications communicate or exchange data. An API call is a request made by application to another to access information or services. When an application requests information from another application, it sends an API call to that application server.
For instance, when your application needs latest user data from HubSpot
Steps involved in API call are:
- The API gets a request for information from the program. This "request" might be a basic search, an effort to log in, or anything more.
- The API checks to see whether the request is legitimate and then sends it to an outside application.
- The external software sends a response to the API, which then sends the data back to the program that asked for it.
Why is API call important?
API calls are very important for applications. Without API calls, apps are unable to exchange data or communicate together seamlessly. Here’s are some of the reasons which it is important:
- API calls help to get instant requests and receive data like live updates, notification, etc.
- API calls are important for integration, whether it is syncing contacts between a CRM and email marketing tools.
- API call helps to save time and reduce errors, by linking apps through APIs.
- APIs ensure data flows smoothly, creating a seamless experience across multiple platforms.
- It also allows the dev team to build on existing apps, add new features or connect to third-party tools.
How Does an API Call Work
Whenever two applications need to communicate or exchange data, they do it using API. API call is the process of sending and receiving API calls, or requesting information.
To enable information exchange between APIs, the dev team needs to provide clear API documentation. This documentation outlines the types of requests the API accepts, the intended use cases, and any specific requirements such as supported protocols, data, schemas, and security measures that third parties must adhere to.
API calls let APIs share functionalities without needing to rewrite code from scratch each individual application. They make it easy to replicate features across multiple platforms and enable seamless data requests from other apps, services and providers. Without APIs, thi kind of interoperability and efficiency would be much harder to achieve.
Here’s what happens behind the scenes when an API call works:
Client sends a request.
The client (which might be a web app, mobile app, or server) submits a request to the API endpoint to start the process. This request usually has:
The API endpoint's URL
- The HTTP method, such as GET, POST, PUT, DELETE, etc.
- Headers, such content type or authentication tokens
- Optional data payload (in most cases, POST or PUT requests)
Server receives the request
The request goes to the server that hosts the API. The request goes via this layer first if there is an API gateway or load balancer. The gateway is in charge of routing, rate limiting, and checking security.
Authentication
The API checks the client's identity by methods such API keys, OAuth tokens, or JWTs. If the client doesn't have permission, the server sends back an error message (such 401 Unauthorized).
Request routing & validation
API routes the request to the appropriate controller or function based on URI and HTTP method. We check the request data to make sure it is in the right format and has all the necessary parameters.
Business Logic execution
The API does the business logic that has to be done. This might be asking database questions, accessing other APIs or services, processing data, or doing math.
Database
If needed, the API can interact with the database or an external service to get data or create, update, or delete data.
Response construction
After data or action is processed, API processes respond. This step usually involves formatting the data into a structured format like JSON or XML.
Response sent back to client
The API provides the response back to the client with an HTTP status code that shows what happened (for example, 200 OK, 404 Not Found, or 500 Internal Server Error).
Client processes the response
The client gets the answer and does something with it, such as showing the user data, changing the UI, or starting other actions.
Real-Life Examples of API Calls
Let's see how payment processing works using an API call that happens in Stripe.
You’re shopping online and ready to pay for your order. When you enter your credit card details and hit “Pay”, here’s what happens is API calls with payment gateway like Stripe.
Client send payment request
Your mobile app or browser collects your payment info like card number, expiry, CVV) securely. When you submit the payment, your app sends an API request to Stripe’s payment API endpoint. This request process includes:
- Payment amount
- Currency
- Card details (encrypted or tokenized for surety)
- Order metadata (order ID, customer info)
Authentication & validation
Stripe's API checks the API key or token given by the e-commerce site to make sure the request is real. It also checks the format of the payment data to make sure it is full and proper.
Fraud & risk checks
Stripe runs automated fraud detection and risk assessment algorithms on transactions to prevent unauthorized or suspicious payments.
Transaction authorization
Stripe uses the banking system to communicate the transaction information to the card network (like Visa or Mastercard) to make sure the card is legitimate and has enough money. Stripe and the banks talk to each other securely using API calls to do this.
Payment confirmation
Once the bank authorizes the transaction, Stripe sends a success response back to your app’s API call, including a unique transaction ID and status. If banks decline due to insufficient funds, invalid cards, etc, Stripe returns an error response explaining why.
Order processing
When your app receives the success response and proceeds to confirm the order, update inventory and display a confirmation message to you.
Webhook notification
Stripe also sends a webhook (a kind of API call) to the e-commerce backend to let it know about the payment status in real time. This keeps the order system in sync even if the app was closed or disconnected.
Why API Calls Matter in Apps and Websites
APIs are the hidden engines which work behind which provide users to interact with clean interfaces on apps and websites, it’s the API calls that quietly perform the hard work in the background.
Here are some reasons why API calls are so important for the performance, functionality, and scalability of digital products:
Enable real-time functionality
API calls allow apps and websites to collect or send data instantly. Whether it's loading a user’s instagram feed, checking bank balance or getting live news all this happens via API requests in real time.
For instance, when you search for a product in Myntra, your query triggers an API call to fetch related listings and displays it as results within milliseconds.
Connect multiple services together
You can’t see an app work in isolation. API calls make it easier to connect multiple services, such as payment gateways, CRM tools, etc. so this helps them to focus on scaling their product then building additional services for their products.
For instance, e-commerce like Myntra or Nykaa integrates with Stripe via API calls to process payments and with Shiprocket via API to handle logistics without building those systems from the ground up.
Save time and cost
Rather than building features from scratch, the dev team uses API to reuse features offered by other platforms which help them to save time, cut down errors and speed up the process.
For instance, instead of building its own login system for their product, SaaS apps can use Google login APIs and deploy the authentication in minutes.
Improve user experience
APIs help apps to work faster and provide interactive and customized solutions for your needs. They help load dynamic content, autofill forms, display user-specific dashboards, and make UX seamless.
For instance, to give a personalized experience Netflix uses APIs to personalize your homepage based on your viewing history, pulling in data from recommendation systems in the backend.
Support automation and scalability
APIs provide businesses to automate workflows and scale operations without increasing manual overhead.
For instance, Whenever a user signs up on a website, an API call can automatically create a contact in HubSpot, trigger a welcome email from Mailchimp, and add the user to a Slack channel for onboarding. All this happens instantly and automatically via background API calls.
Third-party integrations
If your apps offer an API, others can build on top of it. This allows you to expand an ecosystem of integrations, enhancing the value of your product.
For instance, Shopify’ API allows third-party developers to build apps for its app store, driving ecosystem growth and customer retention.
Enable secure data exchange
API calls are structuredized and can be secured with tokens, encryption, and permissions which makes it a safer way to exchange data between systems.
For instance, banking apps use encrypted API calls to fetch account balances without exposing sensitive details to front-end interfaces.
What Tools Use API Calls?
API calls are widely used by every modern digital tool or service. Whether you are using a website or mobile app or running a business application, API calls are happening in the background.
Here are some of the common tools that use API calls?
Social media platforms
Social media apps like Instagram, Facebook, etc use API calls to connect apps, fetch data, and allow sharing.
Example:
Facebook API, lets apps post on your timeline, access profile info (with permission), or log in with Facebook.
Twitter API used to fetch tweets, post updates, or analyze trends.
Instagram API used to schedule posts, pull engagement data, and manage messages.
Payment gateways
Whenever users are paying online, API calls securely send your payment info and get confirmation.
Example
Stripe will process payments, refunds, and billing info via API calls.
PayPall APIs handle transactions, account info and subscriptions.
Razorpay Or Square APLs are used for handling e-commerce payments, UPI, wallets, etc.
Communication tools
Messaging or communications tools like Slack’s APIs allow apps to send instant messages, alerts, and communication.
Example
Twilio API sends SMS, WhatsApp messages or makes voice calls. Uber uses this API to send driver and order notifications.
Slack API used by many apps to send messages, create channels, or set alerts inside a Slack workspace.
Discord API powers bots that manage communities, post alerts or respond to user commands.
CRM and marketing platforms
CRM and marketing applications will use APIs to sync contacts data, update sales pipelines, and automate and automate marketing.
Example
HubSpot API automatically adds leads from forms, sync deals with eternal apps or triggers email campaigns.
Companies use the Salesforce API to fetch customer records, push lead updates or connect with other tools like Google Sheets or Mailchimp.
Mailchimp API used to manage email lists, send newsletters or track campaign performance in real-time.
E-commerce platforms
Online stores need constant updates between inventory, shipping payment, and order systems all powered by APIs.
Example:
Shopify API used to add or remove products, manage inventory, track order, or build custom storefronts.
WooCommerce API helps to sync with shipping partners, send order data to CRMs or update product availability.
AI and automation tools
Automation providers rely almost 100% on APIs to move data between apps and trigger workflows.
Example
Zapier API calls to hundreds of apps to automate tasks, like adding contacts from a form to Google Sheets.
Klamp.io is an embedded iPaaS that uses API connectors to integrate SaaS platforms without code.
What Happens If an API Call Fails?
If an API call fails, the server sends back an error response, usually with status code and message that tells the app something went wrong. apps handle failures with error messages, retries, or fallback options to keep the user experience smooth.
Here’s what might happen in your apps:
- The screen might not load.
- Data doesn't show up.
- Features don’t work.
- An error message pops up.
Conclusion
API calls play an important role in modern apps and websites. They help to connect different services, fetch data, and make real-time actions possible. Understanding how they work and what happens when they fail helps you in building a smoother. More reliable user experience.
FAQ
What happens during an API call?
During an API call one application sends a request to another to access data or perform an action. Server will process the request, verify permission and send it back to Client to continue workflows.
What does an API call look like?
An API call is a request made by a client (such as an app or server) to an API to perform an operation like retrieving data, updating a record, or triggering a process. It basically consists of a request sent over HTTP or HTTPS.
Structure of API Call:
[HTTP Method] [Endpoint URL] HTTP/1.1
Host: [API Host]
Headers: [Key: Value]
Body: [Optional - usually JSON]
Is every app-to-app communication an API call?
No, every app-to-app communication is an API call. While APIs enable apps to communicate with other apps, other communication methods exist. An API call is a specifically refers to a request made to an Application Programming Interface (API), which is a software intermediary
What is the difference between an API and an API call?
API ( Application Programming Interface ) is a set of rules or protocols which allows different software applications to communicate with each other and exchange data. But an API call is a specific request or command sent from one app to another, using an API to access a specific service.
Are API calls safe to use in apps?
Yes, API calls are safe to use in apps, but only if implemented securely.