JSON Formatter, Validator, Viewer: Pick the Right Tool

Compare formatter, validator, viewer, minifier, and diff side by side, with the order to chain them when you're reviewing an API payload.

Which tool for which task

Five JSON tools cover most review work. Formatter for human-readable indentation, validator for strict syntax checking, viewer for exploring large payloads as a collapsible tree, minifier for over-the-wire compactness, diff for comparing two versions semantically.

Format/repair invalid JSONValidate JSON syntax strictlyOpen a JSON tree viewerMinify JSONDiff two JSON files (key order ignored)

Formatter vs repair vs validator

A strict formatter rejects the input on the first syntax error and stops. A smart-repair formatter tolerates common almost-JSON mistakes and then formats the cleaned text. A validator only checks — it doesn't rewrite. Pick by what the input looks like.

Formatter vs repair — what's the differenceHow to format JSONHow to validate JSONPretty-print vs formatHow to minify JSONJSON format examples

Tree viewer vs flat formatter

When the JSON is more than a few screens, a tree viewer beats a flat formatter — you collapse what you don't care about and focus on the part under review. The viewer also makes mismatched bracket pairs obvious.

Viewer vs formatter — when to use whichJSON tree viewer walkthroughCompare two JSON filesValidate JSON before API requests

The specs your tools enforce

Strict validators implement RFC 8259 and ECMA-404. JSONPath tools implement RFC 9535. JSON canonicalization (for signatures) is RFC 8785.

RFC 8259 — JSON standardRFC 9535 — JSONPath standardRFC 8785 — JSON canonicalizationECMA-404 second edition

Recommended path

Use the tools in this order when you're reviewing an unknown JSON payload.

  • 1. Tool: /json-viewer — explore the shape as a tree.
  • 2. Guide: /guides/json-formatter-vs-json-repair — choose strict format vs repair.
  • 3. Blog: /blog/json-viewer-vs-json-formatter — workflow tips.
  • 4. Reference: /news/rfc-8259-json-standard — the grammar your validator enforces.
Open JSON FixCompare JSON changes

JSON repair guides

Topic hubs

  1. JSON Parse Errors: Read the Message, Jump to the Fix
  2. Fix Invalid JSON: From 'What's Wrong' to a Clean File
  3. Repair LLM JSON Output: Handling Almost-JSON from AI
  4. Privacy: JSON Tools That Don't Leave Your Browser
  5. JSON Interop: YAML, CSV, XML, JWT, Schema

Specific guides

  1. How to Decode Base64 Strings (and JWT Payloads)
  2. URL Encoding: Percent-Encode Query Parameters and Paths
  3. Convert YAML to JSON (and Avoid Indentation Errors)
  4. Convert JSON to CSV: Flatten an Array of Objects
  5. Convert JSON to XML: Root Elements, Attributes, and Arrays
  6. Escape JSON as a String Literal (and Decode Double-Encoded JSON)
  7. Fix Trailing Comma in JSON
  8. Fix Single Quotes in JSON
  9. Fix Unquoted Keys in JSON
  10. Repair LLM JSON Output
  11. Fix JSON Parse Error: Expected Property Name
  12. JSON vs JS Object Literal: The Key Differences
  13. Validate JSON Before API Requests
  14. JSON Formatter vs JSON Repair
  15. Fix JSON Unexpected Token Errors
  16. JSON to JavaScript Object Converter