JSON vs XML – Key Differences for Salesforce Developers

Posted by Vinay Vernekar 13th November 2025

When you’re building integrations, the JSON vs XML debate usually pops up pretty early in the design phase. I’ve spent years connecting Salesforce to everything from modern AWS microservices to ancient on-premise ERPs, and honestly, the format you choose can make or break your debugging experience six months down the road.

Both are data interchange formats, but they serve different masters. If you’re working on a modern Salesforce API integration, you’ll probably lean toward JSON. But don’t count XML out just yet. It still has its place in the enterprise world, especially when strict data contracts are a requirement.

Breaking Down the JSON vs XML Comparison

Look, the biggest difference you’ll notice right away is how they look on the screen. JSON (JavaScript Object Notation) is built for speed and simplicity. It uses curly braces and brackets, which makes it feel like second nature if you spend your day writing JavaScript or Apex. It’s lightweight because it doesn’t waste space on closing tags.

XML (eXtensible Markup Language), on the other hand, is much more talkative. It uses tags for everything. While that makes the file size bigger, it also makes it incredibly descriptive. I’ve seen teams struggle with JSON when they need to include a lot of metadata, and that’s where XML actually shines. It’s designed to be a document, not just a data snippet.

Data Types and Validation

One thing that trips people up is how these two handle data types. JSON is pretty smart here. It knows the difference between a string, a number, and a boolean. If you pass a “true” value in JSON, the system knows it’s a boolean. In XML, everything is basically a string unless you have a schema (XSD) to tell the parser otherwise.

In my experience, if you need strict validation where the system rejects a message for having a decimal point in the wrong place, XML is still the king. JSON schemas exist, but they aren’t nearly as baked into the ecosystem as XML validation tools.

Choosing Between JSON vs XML for Your Project

So how do you actually decide? It usually comes down to what you’re connecting to. If you’re building a web app or a mobile tool, go with JSON. It’s faster to parse, uses less bandwidth, and every modern browser handles it natively. It’s the standard for RESTful services.

But if you’re dealing with older bank systems or government APIs, you’re going to see a lot of XML. This usually goes hand-in-hand with SOAP. If you want to understand that side of things better, check out my breakdown of SOAP vs REST to see how these formats fit into different architectural patterns.

Performance and Parsing

Here’s the thing: JSON is almost always faster to parse. Most modern languages have built-in libraries that can turn a JSON string into an object in a few lines of code. XML parsing is a bit more of a chore. You have to load the document tree, which can eat up memory if you’re dealing with massive datasets. If you’re worried about hitting heap limits in Salesforce, JSON is usually the safer bet.

Namespaces and Complexity

Does your data come from five different sources that all use the same field names? XML handles this naturally with namespaces. JSON doesn’t have a built-in way to do this, so you end up creating weird naming conventions like “source1_id” and “source2_id”. It works, but it isn’t as clean as the XML way of doing things.

Key Takeaways

  • JSON is the winner for web and mobile because it’s lightweight and easy for developers to read.
  • XML is better for complex enterprise documents that need strict validation and metadata.
  • JSON supports native data types like numbers and booleans, while XML treats everything as text.
  • XML is more verbose, which means higher bandwidth costs and slower parsing times.
  • Most modern JSON vs XML decisions are driven by the existing tech stack rather than personal preference.

Quick Example Comparison

Here is how a simple employee record looks in both formats. Notice how much extra “noise” is in the XML version.


// JSON Example
{
  "employee": {
    "name": "Jane Doe",
    "role": "Architect",
    "years_exp": 10
  }
}


<! - XML Example - >
<employee>
  <name>Jane Doe</name>
  <role>Architect</role>
  <years_exp>10</years_exp>
</employee>

The short answer for most Salesforce pros? Stick with JSON whenever you have the choice. It’s easier to debug, plays nicely with LWC, and keeps your payloads small. Only reach for XML when the external system demands it or when you’re doing heavy-duty document transformation that requires something like XSLT. Don’t overcomplicate things if you don’t have to.

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