What is JSON?

Matthew Edgar | October 14, 2025

What is JSON? Is it JavaScript? Is it just for schema? How do we read JSON? A brief recap…

Is JSON JavaScript?

JSON is derived from JavaScript but it isn’t JavaScript. It is a language independent. It stands for JavaScript Object Notation and it is really the last two word to focus on: this is a way to notate objects of data.

Unlike JavaScript, JSON does not need to be run or executed. It is plain text. So, AI bots that can’t execute JavaScript can still read JSON. Think of a JSON as formatted text.

On a webpage, schema in JSON is included in a script tag. To distinguish this from regular JavaScript, this tag uses a type attribute to explain what it is.

<script type="application/ld+json">
...json code here...
</script>

The most popular use case for JSON in SEO is schema. However, JSON is widely used on APIs. It is also used to send requests for the MCP and Agent2Agent protocols.

How to Read JSON

JSON is meant to be human readable. That doesn’t mean it is intuitive. Here is a quick overview if how to read JSON…

— Key – This is an identifier and is enclosed in double quotes.

— Value – This is the data assigned to the key.

In the example, foo is the key and bar is the value.

{
 "foo": "bar"
}

Types of Values

We can have different types of values assigned to a key:

— String – Text data in double quotes

"color": "red"

— Number – Numeric values, either integer or decimal, without quotes

"price":23.45

— Object – You can nest JSON in JSON, enclosed by curly braces

"env": {
  "DEBUG": "true",
  "PORT": "8080"
 }

— Array – A list of values in square brackets

 "args": ["server.py", "--verbose"]

— Boolean – Either true or false, no quotes

"active": true

— Null – An empty value is set to null, no quotes

"reviewCount": null

Different Types

Last thing – there are different types of JSON. MCP/A2A use JSON-RPC while schema uses JSON-LD. Both follow the same basic syntax but there are slight differences…

JSON-RPC defines a specific message structure for requests and responses (like requesting data from an API). RPC stands for Remote Procedure Call.

JSON-LD uses a “@context” to map JSON properties to external vocabularies (like schema). LD stands for Linked Data.

Pronunciation

One more tidbit: The inventor, Douglas Crockford, intended for it to be pronounced like the name “Jason” but you can also say “jay-SAWN”.