FJ Tools

JSON Formatter

Validate and pretty-print JSON with syntax highlighting. 100% client-side.

JSON Formatter

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About JSON Formatter

JSON Formatter is a fast, privacy-first browser utility that helps developers, data analysts, and technical writers validate, format, and inspect JSON without sending data to any server. It is optimized for performance and large payloads while keeping the user interface simple and accessible. Paste your JSON on the left, tweak indentation, and see a validated, pretty-printed result on the right. The tool uses the browser's native JSON parser providing instant feedback and helpful error messages for malformed input.

Key features

  • Client-side validation – no uploads, no storage.
  • Pretty-print with configurable indentation (0–8 spaces).
  • Copy formatted JSON with one click.
  • Clear and lightweight UI for mobile and desktop.
  • Works offline in supported browsers (PWA-enabled builds).

Why use this JSON Formatter?

JSON is a ubiquitous data format used across web APIs, configuration files, and data interchange. When JSON is compacted or minified, it becomes hard to read and debug. Our JSON Formatter restores readability and helps identify structural errors quickly. Because the tool runs entirely in the browser, it reduces privacy concerns and avoids the latency associated with server-based formatters.

Examples & usage tips

Use the formatter when copying API responses into documentation, preparing mock data for tests, or when sharing JSON snippets in issue trackers and chat applications. Changing the indentation helps match project style guides (2 spaces for JavaScript projects, 4 spaces for many JSON configs). If your JSON is very large, consider increasing your browser's available memory or using the built-in format incrementally to avoid freezing on low-memory devices.

FAQ

Is my JSON uploaded to a server?

No. All processing happens locally in your browser. Nothing is sent to our servers.

What file sizes are supported?

The practical maximum is limited by your browser and device memory. Typical modern desktops handle multi-megabyte JSON blobs; mobile devices may be lower. For extremely large files, consider chunking or using a desktop utility.

How does this help SEO?

This page includes detailed, crawlable content about the JSON Formatter, descriptive metadata, and JSON-LD structured data so search engines understand the tool and index it for relevant queries like "json formatter", "pretty print json", and "validate json online".

High-value keywords

json formatter, json pretty print, validate json, online json formatter, json validator, pretty json