How to Format and Validate JSON
A step-by-step walkthrough for formatting messy JSON, validating syntax, catching common parsing errors, and converting documents locally.
Understanding JSON Syntax & Validation
JSON (JavaScript Object Notation, RFC 8259) is the lingua franca of web APIs and configuration. While its syntax appears simple, strict parsing specifications cause frequent validation failures when data is modified by hand or copied from logs.
- Single quotes instead of double quotes (
'key') - Unquoted object property names (
id: 101) - Trailing commas after the final element or key
- Unescaped control characters in string literals
- Strings and object keys MUST use double quotes
- Numeric values must not contain leading zeroes
- Arrays and objects must have balanced matching brackets
- Boolean and null values must be lowercase literals
Step-by-Step Walkthrough
Paste or load raw JSON data
Copy your raw or unformatted JSON payload from an API response, config file, or clipboard into the input editor.
Inspect syntax errors and validation alerts
Check the syntax validator indicator. If the document is invalid, inspect the line and character indicators pinpointing missing quotes, trailing commas, or unbalanced braces.
Format with custom indentation or minify
Choose 2-space or 4-space indentation to pretty-print the document, or use Minify to strip all superfluous whitespace for production transport.
Explore the collapsible tree view
Switch to the Tree view to interactively inspect deep object hierarchies, expand or collapse nested nodes, and preserve high-precision numbers with lossless parsing.
Convert JSON to TypeScript, CSV, or YAML
Export your validated JSON data into strongly-typed TypeScript interfaces, clean tabular CSV rows, or human-friendly YAML configuration.
Avoid Silent Numeric Precision Loss
Standard JavaScript uses double-precision floats (IEEE 754) for numbers, meaning any integer larger than 9,007,199,254,740,991 (such as database snowflakes, Twitter IDs, or 64-bit timestamps) gets rounded and corrupted when parsed with standard JSON.parse(). The CODERCOPS JSON Formatter utilizes lossless parsing, ensuring that 64-bit IDs and high-precision scientific figures retain their exact representation through formatting and conversions.
// Frequently Asked Questions
Is formatting JSON online safe for private or customer data?
It is safe only if the tool runs 100% client-side. CODERCOPS JSON Formatter performs all parsing, validation, and conversion directly within your browser. No payloads are ever uploaded to a remote server.
Why won't my JSON parse?
JSON parsing fails on syntax errors such as unquoted object keys, single-quoted strings, or trailing commas after the last element. JSON requires double-quoted keys and strings, and does not allow trailing commas.
Why do large integers change value?
Large integers can parse successfully but lose precision once they exceed JavaScript's safe integer range (9,007,199,254,740,991). The formatter's lossless mode preserves the exact digits of 64-bit IDs and other high-precision numbers instead of rounding them.
How can I convert JSON to TypeScript types?
Use the TypeScript conversion tab inside the JSON Formatter tool. It analyzes property types across objects and arrays, automatically merging structures and generating typed interfaces.