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JSON stays in your browser. We never send your input to a server.
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Pretty-print, then edit attributes by type.
JSON stays in your browser. We never send your input to a server.
Indent and check syntax. Copy the result in one click.
Add and remove nested String / Number / Boolean / Null / Map / List.
Put your JSON into the text area.
Hit Format for pretty output and a quick validation check.
Tweak values in the parameter editor, then copy when ready.
My JSON is a free browser tool to format, validate, and edit JSON.
Paste text and work with nested Maps and Lists more easily.
Syntax checks, formatting, and type-aware editing are included.
No signup or login — completely free.
Your data never leaves the device; nothing is sent to a server.
Even sensitive JSON can be inspected and edited locally.
JSON stands for JavaScript Object Notation. It is a lightweight data-interchange format: structured text that both people and programs can read and write. When someone searches “what is JSON,” the practical answer is usually this—a simple, language-agnostic way to represent objects, lists, and primitive values as text.
JSON is not a programming language. It is a convention for writing data. It grew out of JavaScript object literals, but Python, Java, Go, PHP, Ruby, C#, and many other languages ship first-class support for parsing and serializing JSON. That portability is why JSON became the default payload for so much of the modern web.
JSON’s history starts in the early 2000s. At the time, XML was a common choice for moving data between browsers and servers. XML is expressive and strict, but verbose—heavy to skim and easy to mistype when writing by hand.
Douglas Crockford and others popularized a JavaScript-inspired subset specifically for data exchange and called it JSON. During the AJAX era (Asynchronous JavaScript and XML), many apps used JSON payloads anyway. Front-end developers quickly preferred the shorter syntax and the natural fit with JavaScript objects.
The format was later standardized. On the IETF side, the line runs from RFC 4627 through RFC 7159 to RFC 8259 (The JavaScript Object Notation Data Interchange Format). ECMA International also defines JSON as ECMA-404. Today, “valid JSON” generally means conforming to these specs.
Browsers standardized JSON.parse and JSON.stringify, so teams stopped writing ad-hoc parsers. That ubiquity helped make JSON the lingua franca of web APIs, config files, and service-to-service messages.
JSON values are intentionally limited. The main types are:
{"key":"value"} with curly braces; keys must be strings[1, 2, 3] ordered collections in square bracketstrue / falseStandard JSON has no comments and no trailing commas. Keys must use double quotes. Break those rules and parsers fail—even if the text “looks almost like JSON.” That is why JSON formatting, validation, and pretty-printing are everyday developer chores.
REST and HTTP APIs almost always speak JSON for request and response bodies. The same is true for mobile apps, SPAs, and many microservice boundaries. GraphQL responses are typically JSON as well.
Configuration is another major use: package.json, tsconfig.json, and countless cloud or CI settings. JSON sits between human editing and machine parsing.
Logs, events, and analytics often use JSON Lines / NDJSON—one JSON object per line—because nested fields survive better than flat CSV in many pipelines.
With LLMs, structured outputs and tool-call arguments frequently arrive as JSON. Fixing broken JSON and making nested payloads readable has become even more common, not less.
XML shines for document markup, attributes, and namespaces. JSON focuses on shipping “bags of data” with a short syntax that maps cleanly to objects. YAML prioritizes human readability but has a wide surface area and surprising edge cases. CSV/TSV excel at tables and struggle with deep nesting. Pick the format that matches the job.
Minified one-line responses, deeply nested API payloads, and broken quotes from copy-paste all show up daily. A JSON formatter, syntax check, and type-aware editor speed up debugging and review. My JSON is a free browser tool for that workflow: paste, pretty-print, validate, edit, and copy—without uploading your data to a server.