I Built a JSON Formatter & Validator in the Browser (No Library)

📰 Dev.to · Devanshu Biswas

Learn how to build a JSON formatter and validator in the browser without using any libraries, and understand the process of parsing and re-stringifying JSON data

beginner Published 24 Jun 2026
Action Steps
  1. Parse JSON data using the JSON.parse() method to validate its syntax
  2. Re-stringify the parsed JSON data using the JSON.stringify() method with indentation to format it
  3. Use a textarea or input field to get user input and display the formatted JSON data
  4. Implement syntax highlighting to make the formatted JSON data more readable
  5. Handle errors and exceptions that may occur during the parsing and formatting process
Who Needs to Know This

Frontend developers and web developers can benefit from this tutorial as it provides a simple way to format and validate JSON data in the browser, making it easier to work with JSON data in web applications

Key Insight

💡 The browser's built-in JSON.parse() and JSON.stringify() methods can be used to validate and format JSON data, making it a simple and efficient process

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🚀 Build a JSON formatter and validator in the browser without libraries! 📄️

Key Takeaways

Learn how to build a JSON formatter and validator in the browser without using any libraries, and understand the process of parsing and re-stringifying JSON data

Full Article

Title: I Built a JSON Formatter & Validator in the Browser (No Library)

URL Source: https://dev.to/dev48v/i-built-a-json-formatter-validator-in-the-browser-no-library-4p4n

Published Time: 2026-06-24T14:51:50Z

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Posted on Jun 24

# I Built a JSON Formatter & Validator in the Browser (No Library)

[#webdev](https://dev.to/t/webdev)[#json](https://dev.to/t/json)[#javascript](https://dev.to/t/javascript)[#beginners](https://dev.to/t/beginners)

A JSON formatter sounds like a weekend project — and it is, because the browser does the hard part. Here's a live formatter + validator with syntax highlighting and real error locations, no library.

🧾 **Try it (paste JSON):**[https://dev48v.infy.uk/solve/day15-json-formatter.html](https://dev48v.infy.uk/solve/day15-json-formatter.html)

## [](https://dev.to/dev48v/i-built-a-json-formatter-validator-in-the-browser-no-library-4p4n#format-parse-then-restringify) Format = parse then re-stringify

```
const obj = JSON.parse(input); // validate (throws if invalid)
const pretty =
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