No signup Runs locally Standards-first

Private developer tools for JSON, APIs, and authentication

Format, validate, convert, and inspect your data locally. Nothing leaves your browser.

Paste JSON, a JWT, YAML, CSV, a UUID, a Unix timestamp, or an OpenAPI spec — we'll open the right tool

How It Works

Every tool follows the same three steps: paste your data, it's processed locally in your browser using standard Web APIs (no upload, no account), and you copy or download the result. Nothing you type into a tool is sent anywhere — see the Privacy Policy for specifics.

Search Tools — or press ⌘K / Ctrl K anywhere

JSON & Data

{ }JSON Validator / Formatter

Validate and beautify JSON

🩹JSON Repair

Fix trailing commas, single quotes, and more

🔀JSON Diff

Compare two JSON documents by path

🌳JSON Tree Viewer

Explore JSON as a collapsible tree

API & OpenAPI

↪cURL to Fetch

Convert cURL requests to browser JavaScript

📄OpenAPI Spec Validator

Check required OpenAPI v3 fields

⇆OpenAPI Diff

Classify breaking and additive API changes

👁️OpenAPI Viewer

Read endpoints, responses, servers, and schemas

Authentication & Security

🔑JWT Decoder / Generator

Decode, verify HS/RS/ES signatures, check claims

🗂️JWKS Inspector

Audit every key in a JWKS at once

🗝️JWKS to PEM Converter

Convert a JWKS entry to PEM

🔬PEM Key Inspector

Inspect an RSA/EC public or private key

Code Generation

🔷JSON to TypeScript

Generate TS interfaces from a sample

🐹JSON to Go

Generate Go structs from a sample

☕JSON to Java

Generate nested Java classes from JSON

♯JSON to C#

Generate typed C# models from JSON

Convert & Transform

⇄JSON ⇄ YAML Converter

Convert between JSON and YAML

📊CSV ⇄ JSON Converter

Convert between CSV and JSON

🔁XML to JSON

Convert XML elements, attributes, and repeated nodes

🔡Base64 Encoder / Decoder

Encode or decode text and files

Inspect & Debug

🛡️HTTP Header Analyzer

Check CORS, cache, cookies, and security headers

🧪Regex Tester & Library

Live testing + ready-made patterns

ENVEnvironment Variable Parser

Parse dotenv files and redact likely secrets

⏰Cron Expression Builder

Validate schedules and preview upcoming runs

Related Workflows — or build and share your own →

Cryonel API Guard

Your API shouldn't break silently

Register an OpenAPI spec and Cryonel API Guard watches it for you — re-checking, diffing every version against the last one, and classifying each change by severity instead of collapsing everything into one vague "changed."

🔴 Breaking 🟠 Potentially breaking 🟢 Non-breaking 📝 Docs-only

Why Cryonel?

Every tool on this page runs client-side, in your browser — nothing is uploaded to a server. We keep the interface clean, fast, and free of intrusive ads; no sign-up or credit card required. (Cryonel API Guard, our paid product, is the one exception — see Technical Transparency for exactly what it stores and why.)

Standards

Built against the published specs, not guesswork: JSON (RFC 8259), JWT (RFC 7519), OpenAPI Specification, and UUID (RFC 9562).