Format & validate JSON

Check whether a JSON file is syntactically valid and produce a clean, consistently indented copy without uploading it to a conversion service.

Drop files here or choose themProcessed locally in your browser when supported.

What this tool actually does

Format & validate JSON parses the content as structured data or text before generating the output. JSON, XML, CSV, TSV, Markdown and damaged text are not treated as arbitrary strings where changing a filename would be enough.

How the result is verified

Whenever the format allows it, the generated result is parsed or validated again. Quoted fields, delimiters, XML/JSON structure and text encoding are handled with format-specific checks to reduce outputs that look plausible but cannot be read correctly by the next application.

Limits and fidelity

Limits protect the browser from disproportionate files, rows, columns or cell sizes. The conversion preserves information the destination can represent but does not invent types, relationships or meaning missing from the source. Review critical datasets before replacing the original.

When to use this workflow

Use this workflow when a system requires another representation of the same data, when syntax needs validation or when text displays broken characters. For legal, financial or production-critical information, keep the original and compare a representative sample before relying on the transformed file.

Privacy and final verification

Keep the original file until the output has been reviewed in the destination application or portal. Supported workflows process locally in the browser and enforce bounded size and complexity limits. For Format & validate JSON, verify that the generated format preserves the properties that matter for your use case. For important data, compare a representative sample and confirm that format, content and quality meet the actual requirement before replacing the source file. Also open the generated file in the destination application when compatibility, colour, transparency, layout or compression matters.

What is verified

The complete document is parsed as JSON before output. Invalid syntax is rejected instead of silently rewriting uncertain data.

Safety limits

10 MB input and 12 million decoded characters. Processing happens locally in the browser.

Numeric precision protection

Formatting rejects numeric values that JavaScript would round, including unsafe integers and decimals that cannot be represented exactly in the output. Use a text-preserving workflow when original numeric lexemes must remain unchanged.

Why valid JSON can still be unsafe to reformat

JSON allows deeply nested arrays and objects, but adding indentation at every level can multiply the output size. This formatter stops at 128 nesting levels and 100,000 object/array containers; output is capped at 25 million characters. A syntax check alone would not prevent a browser from exhausting its memory.

How to check the formatted file

Before download, the result is parsed again and its JSON values are compared with the input after parsing. Duplicate property names and decimal numbers that would change through JavaScript numeric conversion are rejected. Formatting can change whitespace and the textual spelling of equivalent numbers; it does not preserve original bytes. For tabular exports use JSON to CSV, which applies additional CSV-specific safety checks.

Example: nested configuration

A configuration such as {"api":{"retry":2,"enabled":true}} becomes readable with two-space indentation. If a service requires exact source bytes or signatures, do not reformat a signed document. For malformed JSON, fix the syntax at its source instead of assuming indentation can repair it.