🔘 JSON Boolean – True/False Values in JSON Explained (2025 Guide)

🧲 Introduction – What is a Boolean in JSON?

In JSON (JavaScript Object Notation), a boolean is a data type that holds one of two values: true or false. Booleans are used to represent binary states—such as on/off, yes/no, enabled/disabled—making them essential for decision-making in data structures, APIs, and configurations.

🎯 In this guide, you’ll learn:

• What boolean values are in JSON
• How to write valid booleans
• How JSON booleans are used in real examples
• How they are handled in JavaScript and other programming languages

✅ JSON Boolean – Format and Syntax

JSON only allows two boolean values:

• true
• false

📌 Syntax Rules:

• Must be written in lowercase (true, false)
• No quotes around the value (unlike strings)
• Cannot be spelled with capital letters (True, False are invalid)
• Cannot use numbers like 1 or 0 as a substitute

🧪 Example – JSON Object with Booleans

{
  "isActive": true,
  "isAdmin": false,
  "subscribed": true
}

🔍 Explanation:

• "isActive": true → The user is active
• "isAdmin": false → The user is not an admin
• "subscribed": true → The user has an active subscription

⚙️ JSON Boolean in JavaScript

When you parse a JSON string containing booleans in JavaScript, they are automatically converted to native JavaScript boolean types.

✅ Example:

const json = '{ "loggedIn": true, "premiumUser": false }';
const user = JSON.parse(json);

console.log(user.loggedIn);     // Output: true
console.log(typeof user.loggedIn); // Output: boolean

🔍 Explanation:

• JSON.parse() converts the JSON string into a JavaScript object
• Boolean values remain true or false, not converted to strings

🚫 Invalid JSON Boolean Examples

Here are some common mistakes that cause invalid boolean values in JSON:

{
  "flag": "true"     // ❌ Invalid – value is a string, not a boolean
}

{
  "enabled": True     // ❌ Invalid – JSON booleans must be lowercase
}

✅ Corrected Version:

{
  "flag": true,
  "enabled": false
}

📌 Summary – Recap & Next Steps

Booleans in JSON are simple and powerful. They let you represent two-state values clearly and reliably across different programming environments.

🔍 Key Takeaways:

• JSON booleans can only be true or false (no quotes)
• Always write them in lowercase
• Do not use "true" as a string or 1/0 as a substitute
• They automatically map to native booleans in JavaScript and most languages

⚙️ Real-world use:

JSON booleans are widely used in user settings, feature toggles, authentication states, and API flags like "success": true.

❓ FAQ – JSON Boolean

❓ What values are valid booleans in JSON?
✅ Only two: true and false. Both must be lowercase and unquoted.

❓ Can I use "true" as a boolean in JSON?
❌ No. "true" is a string, not a boolean. It will be parsed as text.

❓ Are 1 and 0 valid booleans in JSON?
❌ No. JSON does not allow using integers as boolean values.

❓ How do JSON booleans behave in JavaScript?
✅ They become native true or false boolean values when parsed with JSON.parse().