Object to JSON String and Back: Serialize and Deserialize Explained

Oct 19, 2026 · 3 min read · Developer

Programmers say "serialize" and "deserialize" all the time. The ideas are simple. An object lives in your program's memory. You cannot save it to a file or send it over the internet as it is. So you turn it into text. That is serializing. Turning the text back into an object is deserializing.

In JavaScript

const user = { name: "Asha", age: 30 };
const text = JSON.stringify(user);   // '{"name":"Asha","age":30}'
const back = JSON.parse(text);       // { name: "Asha", age: 30 }

In Python the same jobs are json.dumps() and json.loads().

What JSON can hold

JSON understands strings, numbers, true and false, null, arrays and objects. Nothing else. That has some side effects when you stringify:

• Dates become plain text.
• Functions and undefined values are dropped.
• NaN and Infinity become null.

Common errors

Most "Unexpected token" errors come from the text not being real JSON. JSON is stricter than a JavaScript object. Keys must have double quotes. Single quotes are not allowed. Trailing commas are not allowed. Comments are not allowed.

The double-encoded string

Sometimes you parse a string and get another string back. This happens when the data was stringified twice. Parse it a second time and it becomes an object. Our tool detects this and tells you.

Pretty or small?

For reading, add spaces: JSON.stringify(obj, null, 2). For sending over a network, keep it small with no spaces.

Check it with a tool

Paste your object into the Object / JSON String converter on the Developer Converters page. It accepts normal JSON and also JavaScript-style objects with single quotes and unquoted keys, then gives you clean JSON. If the text is broken, it points to the line and column of the problem, so you do not have to hunt for a missing bracket.

Everything runs in your browser, so your data is not sent anywhere.

Frequently asked questions