# I Built JSON Formatter Kit — A Free, Privacy-Focused Developer Toolkit

If you've worked with APIs, backend development, configuration files, or debugging, you've probably had to deal with JSON that looks like this:

{"user":{"id":12345,"name":"John","email":"[e-mail]","roles":["admin","developer"]},"active":true}

It's valid JSON, but it's not particularly pleasant to read.

Usually, the next step is opening a JSON formatter, copying the data, finding a validation tool, checking an error, and then switching to another website when you need to convert the data into another format.

I wanted to make that workflow simpler.

So I built JSON Formatter Kit — a free collection of browser-based tools for developers.

What is JSON Formatter Kit?

JSON Formatter Kit started with a simple idea:

Put the small developer utilities we use every day in one place.

The main tool is a JSON Formatter and Validator, but the project has grown into a broader developer toolkit.

The website currently includes tools for:

• JSON formatting and validation
• JSON viewing and exploration
• JSON comparison and diff
• JSONPath testing
• JSON editing
• JSON sorting
• JSON ↔ CSV conversion
• JSON ↔ XML conversion
• JSON ↔ YAML conversion
• JSON Schema generation
• JSON → TypeScript
• JSON → Python
• JSON → Go
• JSON ↔ Java
• JavaScript formatting
• TypeScript formatting
• PHP formatting
• Java formatting
• GraphQL formatting
• XML tools
• YAML tools
• HTML tools
• CSS tools
• Base64 encoding/decoding
• URL encoding/decoding
• HTML escaping
• JWT decoding
• UUID generation
• Regex testing
• Timestamp conversion
• SQL formatting

There are currently 173 tools available across different categories.

Why another JSON formatter?

There are already plenty of JSON formatting websites.

So I wasn't trying to simply build another page with a textarea and a "Format" button.

I wanted to solve a few problems that I personally find annoying when using online developer tools.

1. Privacy

One of the biggest design decisions was to process data directly in the browser.

When you paste JSON into the formatter, parsing, validation, formatting, and tree visualization happen locally in your browser. The site states that the JSON isn't uploaded to a server.

This is particularly useful when working with:

• API responses
• Configuration files
• Debugging data
• Internal development data
• Large JSON documents
• Data that shouldn't be casually uploaded to third-party services

There is no requirement to create an account just to format JSON.

2. Better error messages

One of the most frustrating parts of working with JSON is finding out that something is invalid without knowing exactly what went wrong.

For example:

{
  "name": "John",
  "age": 30,
  "skills": ["C#", "JavaScript",]
}

The trailing comma makes this invalid JSON.

Instead of simply saying:

Invalid JSON

the formatter identifies the location of the syntax problem and provides an explanation and suggested fix.

The goal is to make the tool useful not only for formatting JSON, but also for debugging JSON.

3. Code view and tree view

Formatted JSON is useful, but sometimes you need to understand the structure of a large document.

JSON Formatter Kit provides a tree explorer where you can expand and collapse objects and arrays, search through keys and values, and inspect individual nodes.

You can also copy JSON paths and values from the tree.

For example, instead of searching through thousands of lines for:

customer.orders[12].items[3].price

you can navigate the structure visually.

4. Large JSON files

Another area I wanted to focus on was handling larger JSON documents.

The application uses background processing and virtualized rendering so that large documents don't require rendering everything into the page at once.

The current implementation supports files up to 200 MB per file, with the site noting that files in the tens-of-megabytes range work well on modern laptops.

That's useful when dealing with:

• Large API responses
• Exported datasets
• Logs
• Configuration dumps
• Database exports

5. Preserving numbers and formatting

There is another subtle problem with JSON tools.

Consider a large integer:

{
  "id": 9223372036854775807
}

Depending on how a tool parses JSON, large numbers can potentially lose precision.

JSON Formatter Kit is designed to preserve numbers, decimals, and string escapes rather than silently rewriting them while formatting. According to the site's documentation, formatting changes whitespace rather than the underlying values.

That distinction matters when JSON contains IDs, financial values, timestamps, or other data where changing the representation could be problematic.

More Than a JSON Formatter

Although JSON is where the project started, I didn't want to stop there.

Developers constantly move between different formats.

For example, you might receive:

API → JSON → TypeScript interface

or:

JSON → CSV → Excel

or:

JSON → YAML → Configuration

Instead of searching for a different website every time, the goal of JSON Formatter Kit is to provide those utilities in one place.

JSON Converters

The site includes converters such as:

• JSON to CSV
• CSV to JSON
• JSON to XML
• XML to JSON
• JSON to YAML
• YAML to JSON

These are particularly useful when working with APIs, configuration files, data exports, and integrations.

Generate Code From JSON

Another category I'm particularly interested in is turning data into code.

For example, a JSON response can be used to generate structures for languages such as:

• TypeScript
• Python
• Go
• Java

There is also a JSON Schema generator.

This can save developers from manually creating models when working with API responses.

Developer Tools Beyond JSON

The project is gradually becoming a general-purpose developer toolkit.

There are tools for:

Code formatting

• JavaScript
• TypeScript
• PHP
• Java
• GraphQL

XML

• XML Formatter
• XML Validator
• XML Viewer
• XML Minifier

YAML

• YAML Formatter
• YAML Validator
• YAML Viewer

HTML

• HTML Formatter
• HTML Viewer
• HTML Validator
• HTML Minifier

CSS

• CSS Beautifier
• CSS Minifier
• SCSS → CSS
• CSS → SCSS

Encoding

• Base64 Encode/Decode
• URL Encode/Decode
• HTML Escape
• JSON Escape/Unescape

Developer utilities

• JWT Decoder
• UUID Generator
• Regex Tester
• Timestamp Converter
• SQL Formatter

The idea is to make the site useful even when the task isn't specifically related to JSON.

Everything Runs in the Browser

One of the principles behind the project is:

If a tool doesn't need a server, don't use a server.

For many of these utilities, processing can happen entirely inside the browser.

That provides a few benefits:

• No account required
• No file upload required
• Faster processing for many operations
• Better privacy
• Reduced server infrastructure
• Tools can continue working offline after loading

For the main JSON formatter, the site specifically states that parsing, validation, formatting, and tree visualization happen in the browser.

A Small Example

Suppose an API returns:

{"id":1001,"name":"Alice","department":"Engineering","projects":[{"name":"API","status":"active"},{"name":"Dashboard","status":"completed"}]}

Instead of manually adding indentation, you can paste it into JSON Formatter Kit and get:

{
  "id": 1001,
  "name": "Alice",
  "department": "Engineering",
  "projects": [
    {
      "name": "API",
      "status": "active"
    },
    {
      "name": "Dashboard",
      "status": "completed"
    }
  ]
}

You can then switch to the tree view, search the document, copy values or paths, sort object keys, or download the formatted JSON.

Keyboard Shortcuts

For developers who prefer staying on the keyboard, the formatter also includes shortcuts.

For example:

Ctrl + Enter          Format JSON
Ctrl + Shift + Enter  Minify JSON
Ctrl + O              Open a file
Ctrl + S              Download output
Ctrl + Alt + C        Copy output
Ctrl + F              Search
Ctrl + Z              Undo
Alt + 1 / 2 / 3       Code / Tree / Stats

These are small features, but they make the tool much faster to use when you're working with JSON repeatedly.

What I'm Trying to Build

The long-term idea isn't just:

"another JSON formatter."

I want JSON Formatter Kit to become a developer toolbox that you can bookmark and return to whenever you need a quick utility.

Instead of searching:

JSON formatter
JSON validator
JSON to CSV
JWT decoder
UUID generator
Base64 decoder
Regex tester
SQL formatter
XML formatter

the idea is to have these utilities available from one place.

The focus is on making each tool:

• Fast
• Simple
• Free
• Privacy-friendly
• Easy to understand
• Useful without registration

What's Next?

The project is still evolving.

I'm continuing to improve existing tools, add new developer utilities, improve performance for large files, and make the overall experience better on desktop and mobile.

There are also plenty of possible tools I'd like to add based on what developers actually need.

If you use developer tools regularly, I'd love to hear what utilities you think should be included.

Maybe there's a small repetitive task you perform every day that could be turned into a simple browser tool.

Try It

If you work with JSON, APIs, configuration files, or other developer data, you can try the toolkit here:

👉 https://jsonformatterkit.com/

It's free to use, and the main JSON tools run directly in your browser.

If you try it, I'd be interested to hear what you think — especially which tools you find useful and what you'd like to see added next.

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Built for developers, by developers — one small tool at a time.