JSON Forge — six JSON utilities in one browser tab.
Format, validate, diff payloads, decode JWTs, extract with regex, convert to CSV. Everything you need for API testing and JSON debugging — zero install, zero sign-up.
Six tools. Zero switching cost.
Format & Validate
Paste any JSON payload — minified, malformed, or deeply nested — and get back a formatted, syntax-highlighted tree. Validation errors show exact line and path.
Diff Two Payloads
Paste two JSON responses side-by-side and see added, removed, and changed keys highlighted. Essential for API regression testing when you need to catch schema drift between versions.
JWT Decoder
Paste any JWT and instantly decode the header, payload, and signature — without a secret key. Expiry shown as a human-readable timestamp. No server call, no token logging.
Regex Extraction
Run regex patterns against any JSON string to extract specific values, validate formats (emails, UUIDs, phone numbers), or build assertions for your automation scripts.
JSON to CSV
Flatten any JSON array to a CSV table — one row per object, headers auto-detected from keys. Useful for test data generation, API response analysis, and stakeholder reporting.
Schema Validator
Validate a JSON payload against a JSON Schema (draft-07). See which properties are missing, wrong type, or violate constraints — invaluable for API contract testing.
Where QA teams deploy JSON Forge.
API Response Regression
After deploying an API change, diff the response payload against a baseline snapshot. The Diff tool surfaces added or removed fields, type changes, and nested value shifts — before QA misses them in manual testing.
JWT-Based Auth Debugging
When an auth test fails, decode the JWT to inspect claims, expiry, and scope in the token. No external tool needed — decode directly in the browser without sending the token anywhere.
Test Data Preparation
Convert API response arrays to CSV for loading into test data files, spreadsheets, or data-driven test frameworks. Handles nested objects with key flattening.
Frequently asked questions.
Is JSON Forge completely free?
Yes — all six tools in JSON Forge are free with no account required. Open the page and start working immediately.
Does the JWT decoder send my token to a server?
No. JWT decoding happens entirely in your browser using JavaScript. No token data is transmitted to any server. Safe for use with real JWTs in development environments.
What does the JSON Diff tool highlight?
The Diff tool highlights added keys (green), removed keys (red), and changed values (yellow) between two JSON payloads. It performs a deep recursive comparison — detecting nested changes that string diff tools miss.
How does JSON to CSV handle nested objects?
Nested objects are flattened using dot notation — a nested key like user.address.city becomes user.address.city in the CSV header. Arrays within objects are serialized as strings.
What JSON Schema draft does the validator support?
The Schema Validator supports JSON Schema draft-07, which covers all common validation keywords: type, required, properties, additionalProperties, enum, pattern, minimum, maximum, and oneOf/anyOf/allOf.
Can I use regex extraction for UUID or email validation?
Yes. Run any regex pattern against your JSON string. The tool returns all matches with their capture groups — useful for validating ID formats, extracting email addresses from response bodies, or checking timestamp formats.
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