How does work REST API Integration Between Salesforce and Third-Party Applications | Salesforce REST API example

One of the greatest strengths of Salesforce is its ability to integrate with third-party applications through REST API. Whether you’re connecting with a custom web app, an ERP, a payment gateway, or a marketing platform REST API enables smooth two-way communication.

In this article, you’ll learn how to:

Authenticate into Salesforce from a third-party app.
Send a REST API request from the external app to Salesforce
Display Salesforce data on your own UI using HTML + JavaScript

🔁 Integration Workflow

Authenticate using OAuth 2.0 and get an access token.
Use the token to call Salesforce REST API endpoints.
Fetch or push data to/from the external application.

💻 HTML + JavaScript Code Example (Read from Salesforce)

⚠️ Ensure you have a valid accessToken and instanceUrl.

👉 Download Free Ebook →

👉 Get Free Course →

```
  <!DOCTYPE html>
```
```
<html>
```
```
<head>
```

  <title>Salesforce Third-Party Integration</title>

```
</head>
```
```
<body>
```
```
  <h2>GET Contacts FROM Salesforce</h2>
```

  <button onclick="fetchContacts()">Fetch Contacts</button>

```
  <div id="response"></div>
```
```
 
```
```
  <script>
```
```
    async FUNCTION fetchContacts() {
```

      const accessToken = "YOUR_ACCESS_TOKEN";

      const instanceUrl = "https://yourInstance.salesforce.com";

```
 
```

      const response = await fetch(`${instanceUrl}/services/data/v59.0/query?q=SELECT+Id,FirstName,LastName+FROM+Contact+LIMIT+5`, {

```
        method: "GET",
```
```
        headers: {
```

          "Authorization": `Bearer ${accessToken}`,

          "Content-Type": "application/json"

```
        }
```
```
      });
```
```
 
```

      const RESULT = await response.json();

      document.getElementById("response").textContent = JSON.stringify(RESULT, NULL, 2);

```
    }
```
```
  </script>
```
```
</body>
```
```
</html>
```

✅ Conclusion

REST API allows third-party applications to communicate with Salesforce in real-time, making it ideal for automation, real-time dashboards, or CRM synchronization. With proper authentication and API calls, you can fetch or manipulate any Salesforce object easily.

In the next tutorial, we’ll show how to push data from a third-party app to Salesforce using POST method.

FAQ (Frequently Asked Questions)

How does the REST API work in Salesforce?

Each resource in REST API is identified by a named Uniform Resource Identifier (URI) and is accessed using standard HTTP methods (HEAD, GET, POST, PATCH, DELETE). REST API is based on the usage of resources, their URIs, and the links between them. You use a resource to interact with your Salesforce org.

How does Salesforce integrate with other applications?

The integration tool will connect to Salesforce using APIs and authentication. Connections to target apps must also be configured. With connections in place, data fields must be mapped between Salesforce and external objects. This mapping ensures data aligns correctly on syncing.

What is the difference between connect REST API and REST API in Salesforce?

Connect REST API differs from REST API in multiple ways, including: Data is structured for rendering on websites and mobile devices. Returned information is localized to the user's time zone and language. Changed values that are tracked in a feed are returned as value-pair representations.

Vijay Kumar

Hi, This is Vijay Kumar behind the admin and founder of w3web.net. I am a senior software developer and working in MNC company from more than 8 years. I am great fan of technology, configuration, customization & development. Apart of this, I love to write about Blogging in spare time, Working on Mobile & Web application development, Salesforce lightning, Salesforce LWC and Salesforce Integration development in full time. [Read full bio] | | The Sitemap where you can find all published post on w3web.net

How does work REST API Integration Between Salesforce and Third-Party Applications | Salesforce REST API example | Tech W3Web Salesforce Tutorial