JSON Playground

What Is a JSON Playground?

JSON is the default language of APIs, configuration files and data exchange. It is simple enough to read by hand and strict enough that a single stray character breaks an entire document. A JSON playground exists to answer three questions quickly: is this valid, what does it contain, and where exactly is the problem?

Validation You Can Trust

Rather than approximating the specification with a regular expression, this tool uses the browser's own JSON.parse. That means the verdict here matches the verdict from any compliant parser — including the one in the service that rejected your payload. Strict JSON allows objects, arrays, strings, numbers, booleans and null, with double-quoted keys and no trailing commas. Comments are not part of the format.

When parsing fails, browsers report a character offset, which is nearly useless in a 4,000-line file. The playground converts that offset into a line and column by counting newlines up to the failure point, so the message tells you where to look.

Structure Statistics

Valid documents are walked recursively to produce a small profile: total keys, number of objects, number of arrays, maximum nesting depth and null count, plus the byte size both minified and pretty-printed. These numbers are practical, not decorative:

• Depth predicts trouble with flatteners, database columns and UI rendering.
• Key count hints at whether a payload is a record or a bulk export.
• Minified vs pretty size shows exactly what whitespace costs on the wire.
• Null count flags optional fields that consumers must handle defensively.

Safe Path Queries

Extracting one value from deep structure is a constant need. The path field accepts dot and bracket notation — plan.seats, tools[1].slug, meta.tags[0] — and resolves it by walking the parsed object step by step. There is no eval, no expression parser and no dynamic code execution, which keeps the feature completely safe even with untrusted input.

Everyday Uses

Debugging an API response that a client rejects. Reviewing a configuration file before deploying it. Confirming a field exists at the exact path a mobile app expects. Prettifying a minified payload from network logs so a colleague can read it. Measuring how much bandwidth pretty-printing would add to a high-traffic endpoint. Checking whether a nested array contains the number of items a report claimed.

Why Local Processing Is the Right Default

API payloads routinely contain tokens, customer names, order details and internal identifiers. Pasting that into a service that posts it to a server creates a data-handling problem where none needed to exist. Here, every step happens in your browser, so the sensitive content never leaves your device — and the tool keeps working when you are offline.

Privacy

Parsing, formatting, analysis and path lookups run entirely in the browser. Your document is stored only as a local draft in this browser and is cleared by the Reset button.

Transform data programmatically in the JavaScript Runner, query tabular data with the SQL Runner, or convert formats using the JSON to CSV Converter.

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