JSON is the universal language of APIs, config files, and data exchange. But raw JSON — compact, unindented, all on one line — is nearly impossible to read, debug, or edit by hand. A single missing comma or trailing comma can break an entire API response, and finding that error in a minified block of text is maddening.
That is why we built our free JSON Tools suite. Paste any JSON and instantly format it with proper indentation, validate the syntax, minify it for production, convert it to TypeScript interfaces or Go structs, or explore it as an interactive tree — all in your browser, no signup required.
What Is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data format that is easy for humans to read and write and easy for machines to parse and generate. It was introduced by Douglas Crockford in the early 2000s and has since become the de facto standard for data exchange on the web.
JSON supports two primary structures:
- Objects: Unordered collections of name-value pairs, wrapped in curly braces
{} - Arrays: Ordered lists of values, wrapped in square brackets
[]
Values inside JSON can be strings, numbers, booleans (true or false), null, or nested objects and arrays. Unlike JavaScript objects, JSON keys must be double-quoted strings, and trailing commas are not allowed.
Why You Need a JSON Formatter
Almost every developer works with JSON daily — API responses, configuration files (package.json, tsconfig.json), database exports, and log files. Without formatting, JSON looks like this:
{"users":[{"id":1,"name":"Alice","active":true,"roles":["admin","editor"]},{"id":2,"name":"Bob","active":false,"roles":["viewer"]}],"meta":{"total":2,"page":1,"limit":10}}That is valid JSON, but good luck spotting an error or understanding the structure at a glance. A formatter transforms it into this:
{
"users": [
{
"id": 1,
"name": "Alice",
"active": true,
"roles": ["admin", "editor"]
},
{
"id": 2,
"name": "Bob",
"active": false,
"roles": ["viewer"]
}
],
"meta": {
"total": 2,
"page": 1,
"limit": 10
}
}The formatted version reveals structure, makes errors obvious, and allows you to reason about the data. But a modern JSON tool should do far more than just add whitespace.
What Our JSON Tools Suite Does
Most online JSON formatters stop at beautification. Ours goes further, because real developer workflows need more:
1. Format & Validate
Paste any JSON and click Format to get properly indented output with 2-space or 4-space indentation. If your JSON is invalid, the validator pinpoints the exact line and character where the error occurs — missing comma, unmatched quote, unexpected token, or trailing comma. No more guessing.
2. Minify
Remove all whitespace to produce the smallest possible JSON string. This is essential for production APIs where every byte counts, or when storing JSON in databases and localStorage with size constraints.
3. Convert to TypeScript
Paste a JSON object and get fully typed TypeScript interfaces with proper type inference: string, number, boolean, nested objects, and arrays. Each unique object shape gets its own exported interface. No more hand-writing types to match API responses.
4. Convert to Go Structs
Generate idiomatic Go struct definitions from any JSON, complete with PascalCase field names, correct Go types (string, int, float64, bool), and json:"fieldName" struct tags for unmarshaling.
5. Tree View
Explore deeply nested JSON through an interactive collapsible tree. Click arrows to expand or collapse objects and arrays. This is the fastest way to understand a large JSON document without scrolling through hundreds of lines.
How to Format JSON: Step by Step
- Copy your JSON: Grab the raw JSON from an API response, log file, or config file
- Paste into the editor: Open JSON Tools and paste into the textarea
- Click Format: Choose 2-space or 4-space indentation. The tool validates and beautifies instantly
- Copy the result: Select and copy, or use the copy button if available
If your JSON is invalid, the tool will highlight the error location and describe what is wrong — for example, "Unexpected token } at line 12, column 34" or "Trailing comma not allowed."
JSON Validation: Common Errors and Fixes
Invalid JSON is one of the most common causes of API failures and configuration errors. Here are the mistakes we see most often:
| Error | Invalid Example | Fix |
|---|---|---|
| Trailing comma | {"a": 1,} | Remove the last comma: {"a": 1} |
| Unquoted keys | {a: 1} | Quote the key: {"a": 1} |
| Single quotes | {'a': 1} | Use double quotes: {"a": 1} |
| Comments | {"a": 1 // comment} | Remove comments; JSON does not support them |
| Undefined | {"a": undefined} | Use null instead: {"a": null} |
| NaN / Infinity | {"a": NaN} | Use null or a string representation |
| Unescaped quotes in strings | {"msg": "He said "hi""} | Escape inner quotes: {"msg": "He said \"hi\""} |
| Missing comma between items | [1 2 3] | Add commas: [1, 2, 3] |
JSON Minification: When and Why
Minified JSON removes all unnecessary whitespace — spaces, line breaks, and indentation — to produce the smallest valid JSON string. This matters in several scenarios:
- API responses: Reducing payload size lowers bandwidth costs and improves response time, especially for mobile users
- localStorage / sessionStorage: Browser storage is limited (typically 5-10 MB). Minifying JSON before storing it maximizes available space
- Embedded config: When bundling JSON into JavaScript or HTML, minification reduces bundle size
- Database storage: Storing JSON in text columns is more efficient when minified
Our minifier strips all whitespace while preserving data integrity. The output is guaranteed to parse identically to the input.
JSON to TypeScript: Automatic Type Generation
One of the most tedious tasks in TypeScript development is writing interface definitions to match JSON API responses. Our converter automates this:
- Paste any JSON object or array
- Click Generate TypeScript
- Get properly typed
interfacedeclarations with inferred types
Example input:
{
"id": 42,
"name": "Project Alpha",
"active": true,
"tags": ["api", "docs"],
"owner": {
"id": 7,
"email": "alice@example.com"
}
}Generated output:
export interface Root {
id: number;
name: string;
active: boolean;
tags: string[];
owner: Owner;
}
export interface Owner {
id: number;
email: string;
}The converter handles nested objects, arrays of objects, mixed arrays, and optional fields. It produces clean, idiomatic TypeScript you can drop directly into your project.
JSON to Go Structs: Idiomatic Go Code
Go developers face a similar problem: converting JSON API responses into struct definitions with correct types and JSON tags. Our generator produces:
- PascalCase struct field names (exported by default)
- Correct Go types:
string,int,float64,bool,interface{}for mixed types json:"fieldName"tags for standard library unmarshaling- Nested structs for nested objects
Example input:
{
"user_id": 99,
"display_name": "Bob",
"settings": {
"theme": "dark",
"notifications": true
}
}Generated output:
type Root struct {
UserID int `json:"user_id"`
DisplayName string `json:"display_name"`
Settings Settings `json:"settings"`
}
type Settings struct {
Theme string `json:"theme"`
Notifications bool `json:"notifications"`
}JSON Tree Viewer: Explore Complex Documents
When you are working with large JSON files — think API schemas, database dumps, or configuration exports — even formatted JSON can be overwhelming. The Tree Viewer transforms JSON into a collapsible hierarchy:
- Objects are expandable nodes showing their keys
- Arrays show item count and expand to reveal elements
- Primitive values display inline with their type indicated
- Click any arrow to collapse a section and focus on what matters
This is especially useful for exploring unfamiliar APIs, inspecting webhook payloads, or reviewing exported data where you need to understand structure before writing code to process it.
JSON Cheat Sheet
Data Types
| Type | Example | Notes |
|---|---|---|
| String | "hello" | Double quotes only. Use \ to escape special characters |
| Number | 42, 3.14, -99 | No quotes. Supports integers, floats, and negatives |
| Boolean | true, false | Lowercase, no quotes |
| Null | null | Represents absence of value |
| Object | {"a": 1} | Unordered key-value pairs. Keys must be strings |
| Array | [1, 2, 3] | Ordered list. Values can be mixed types |
Escape Characters
| Sequence | Meaning |
|---|---|
\\ | Backslash |
\" | Double quote |
\n | Newline |
\t | Tab |
\r | Carriage return |
\b | Backspace |
\f | Form feed |
\uXXXX | Unicode character (e.g., A = A) |
Real-World Use Cases
- API development: Format and validate request/response payloads during development and testing
- Debugging: Paste error responses from APIs to quickly inspect structure and spot missing fields
- Type generation: Convert third-party API documentation examples into TypeScript or Go types for your project
- Config editing: Format
package.json,tsconfig.json, or cloudformation templates for readability - Log analysis: Pretty-print structured JSON logs to understand error traces and request flows
- Database exports: Inspect exported JSON dumps before importing or transforming them
- Webhook inspection: Paste webhook payloads into the tree viewer to understand event structure
- Production optimization: Minify JSON config files and API payloads to reduce size
Frequently Asked Questions
Is this JSON formatter free?
Yes, completely free. No signup, no usage limits, no API calls. Everything runs in your browser.
Does this tool send my data to a server?
No. All JSON formatting, validation, conversion, and tree viewing happens 100% client-side in your browser using JavaScript. Your data never leaves your machine. This makes it safe for sensitive data like API keys, personal information, and proprietary config files.
What is the difference between formatting and validating?
Formatting (beautification) adds indentation and line breaks to make JSON readable. Validation checks whether the JSON is syntactically correct according to the JSON specification. Our tool does both simultaneously — you get formatted output only if the input is valid. If it is invalid, you get a clear error message instead.
Can I convert JSON to other languages besides TypeScript and Go?
Currently we support TypeScript interfaces and Go structs, which are the two most commonly requested conversions. Python dataclasses, Rust structs, and Java classes are on our roadmap.
Does the TypeScript converter handle optional fields?
The converter infers types from the example JSON you provide. If a field appears in some objects but not others within an array, the converter will mark it as optional (field?: type). For maximum accuracy, provide a representative sample that includes all possible fields.
What is the maximum JSON size I can process?
The tool runs entirely in your browser, so the limit is determined by your device's memory. In practice, JSON files up to several megabytes work fine. For extremely large files (10+ MB), consider using a command-line tool like jq.
Can I sort JSON keys alphabetically?
Yes. In the Format & Validate tab, click the Sort Keys button to recursively sort all object keys alphabetically. This is useful for comparing two JSON objects or ensuring consistent output.
Try It Now
No signup, no installation, no server calls. Open JSON Tools, paste your JSON, and format it instantly. Validate syntax, minify for production, generate TypeScript or Go types, or explore with the tree viewer.
Looking for more free developer tools? Browse our full tools directory — including Cron Expression Generator, Regex Tester, and JWT Decoder.