Privacy: JSON Tools That Don't Leave Your Browser

JSON, JWT, and Base64 tools that process every byte locally in your browser tab — no upload endpoint, no server-side logs of pasted payloads.

When you land here

You're about to paste a webhook payload, an API sample, or a JWT into a formatter and you're not sure if it stays on your machine. Every tool on this hub runs entirely in your browser — no upload endpoint exists. Use these for production samples, customer data, or anything you wouldn't paste into a random search box.

Repair JSON locallyValidate JSON locallyView JSON as a tree locallyDecode a JWT locally (claims, not signature verification)Base64 encode/decode locally

What 'local' means here

The repair, validation, format, minify, copy, and diff actions run entirely on the page. The tool does not have an upload endpoint and does not need one. Still remove secrets before pasting examples anywhere — the local guarantee covers this site, not your browser extensions or the next tab.

Sensitive JSON in local tools (blog)Validate JSON before API requests (guide)Fix JSON online — local workflowHow to decode a JWT (without verification)Decode Base64 strings and JWT payloadsBase64 is encoding, not encryption

Why this matters

Several JSON-tooling incidents in recent years have shown that paste-to-format sites can log payloads, leak them through ad networks, or pass them through vulnerable parsers. The reference column tracks the incidents and the bugs.

Online JSON formatter data leak (Snyk research)Fedify JSON-LD signature bypassjq NUL-byte validation bypass (CVE)jq path-depth CVE in JSON pipelinesYAML parser stack-overflow depth limit

Recommended path

If you treat pasted JSON as confidential, walk the stack in this order.

  • 1. Tool: / — repair invalid JSON locally.
  • 2. Guide: /guides/validate-json-before-api-requests — the local validation workflow.
  • 3. Blog: /blog/sensitive-json-local-tools — what 'local' actually buys you.
  • 4. Reference: /news/online-json-formatter-data-leak — the incident that motivates the local-first design.
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. JSON Formatter, Validator, Viewer: Pick the Right Tool
  4. Repair LLM JSON Output: Handling Almost-JSON from AI
  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