Simple online tools for developers

Fast. Clean. Private. No sign-up required.

Available Tools

M

Markdown Editor

Write and preview Markdown with live rendering

{ }

JSON Formatter

Format, validate, and beautify JSON data

Y

YAML Validator

Validate and convert YAML to JSON

B64

Base64 Encoder

Encode and decode Base64 strings

API

API Tester

Test APIs with validation and cURL support

JWT

JWT Debugger

Decode and inspect JWT tokens

ID

UUID Generator

Generate and validate UUIDs (v1, v4, v7)

CRN

Cron Builder

Build and preview cron expressions

Why callstack.cloud?

Lightning Fast

No heavy frameworks. Just fast, efficient tools.

100% Private

Everything runs in your browser. No data leaves your device.

Clean UI

Distraction-free interface. Focus on what matters.

Free Forever

Core tools are free. No sign-up. No ads.