Free to Use · v1.0
JSONLab

The JSON
Laboratory

Format, validate, convert and decode JSON like a scientist. A fast, offline-first desktop tool built for developers.

🪟 Windows
🍎 macOS
🐧 Linux
JSONLab application screenshot
5
Output formats
Saved entries
0
Cloud dependencies
3
Desktop platforms
100%
Offline & private

Watch JSONLab do the work.

Format, convert and validate JSON in seconds — no setup, no internet, no friction.

JSONLab · Format & Translations demo

Every JSON tool you need,
in one lab.

From quick formatting to deep format conversion — JSONLab handles it without any setup, login, or internet connection.

🎨
Syntax Highlighting
Keys, strings, numbers, booleans and null values each get a distinct color via a built-in tokenizer for instant readability.
Validate & Auto-fix
Pinpoints errors by line and column. Auto-fix silently repairs trailing commas, single-quoted strings, and unquoted keys.
🔄
Multi-format Conversion
Convert JSON ↔ YAML, XML, TOML, and .properties in both directions. Preview any format before you copy or export.
📁
Import & Export Files
Import any supported file from disk; export any entry in any format with one click. Format auto-detected from extension.
🔍
Deep Search
Search across all saved entries by name, JSON key, or value — including deeply nested structures, with match badges.
🏠
Local-first Storage
Everything stored locally — no account, no cloud, no telemetry. Your data stays entirely yours, forever.

Built for clarity,
designed for speed.

🔑 JWT Decoder

Decode tokens
in one click.

Paste any JWT and instantly see the header, payload and signature decoded — with human-readable timestamps, expiry status and claim descriptions. No network calls. Ever.

  • Algorithm, type, key ID from header
  • All payload claims with descriptions (sub, iss, aud, exp…)
  • Timestamps as human-readable dates + relative time
  • Expired / valid / no-expiry status badge
  • Copy payload as formatted JSON
🔑
JWT Decoder · signatures not verified
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiI0MiIsIm5hbWUiOiJBZGEgTG92ZWxhY2UiLCJleHAiOjE3OTUwMDAwMDB9.c2lnbmF0dXJlX2hlcmU
✓ HS256 ⏱ Expires in 11 months
Header
alg "HS256"
typ "JWT"
Payload
sub "42"
name "Ada…"
exp 1795000000May 13 2026 · in 11 months

From paste to insight
in four steps.

1
Paste or Import
Paste JSON, YAML, XML, TOML or .properties — or import directly from a file on your disk.
2
Format & Validate
One click pretty-prints, validates, and highlights syntax. Auto-fix repairs common mistakes.
3
Convert & Preview
Switch to YAML, XML, TOML or .properties with a chip — live preview updates instantly.
4
Save & Recall
Name the entry and save it locally. Find it later in seconds with the deep search bar.

Love JSONLab? Buy us a coffee.

JSONLab is completely free to use. If it saves you time, consider supporting its development so we can keep building great tools for developers.

💳
PayPal
Email amit@thehobbyist.in
Donate via PayPal
📱
UPI  (India)
UPI QR Code
Scan with PhonePe, GPay, Paytm
or any UPI app

Check out our other apps

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Ready to use the lab?

Free to use, offline-first, no login required. Works on Windows, macOS and Linux.

Also available for macOS and Linux. Contact us at amit@thehobbyist.in for more download options.

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