MJJ Tools

Name: MJJ Tools
Author: Jacky Chen

Under review

Free online tools for converters, math, and developers

Provides 160+ free online calculators, converters, and developer utilities such as JSON formatters and regex testers, all processed privately in the browser without registration.

Built by Jacky Chen · Productivity · Developer Tools · Education · Free

Coming soon on Launch Llama Tools

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Jacky Chen (Joined Nov 2026)

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Provides 160+ free online calculators, converters, and developer utilities such as JSON formatters and regex testers, all processed privately in the browser without registration.

About

MJJ Tools is a collection of free online calculators, converters, and developer utilities. Its categories include Daily Tools, Developer Tool, Math Tool, Academic Tool, Finance Tool, Gaming, Translation, and Security. Users can format JSON, test regular expressions, encode or decode Base64, and generate QR codes directly from a web browser. No account is required to use the tools. A My Favorites list helps users return to frequently used utilities.

Key Features

Run 160+ free calculators, converters, and generators directly in the browser
Format, validate, and decode JSON, Base64, YAML, and JWT data
Test regex patterns and convert curl commands into code in multiple languages
Generate cron expressions, UUIDs, QR codes, and barcodes
Calculate mortgage payoffs, board feet, and voltage drop
Save frequently used tools to a My Favorites list

Use Cases

Convert cooking measurements such as grams to tablespoons or Fahrenheit to Celsius for recipes
Debug regex patterns or decode JWT tokens while building software
Estimate a mortgage payoff or prorate rent for personal finance decisions

From the founder

Who it's for

“For developers and students who need free browser utilities.”

About me

“I maintain free tools for everyday calculations and developer tasks.”

— Jacky Chen, founder of MJJ Tools

Who it is for

Software developers who need regex testers, JSON formatters, and cron generators
Students who need AP score, GPA, and grade curve calculators
Home cooks and DIY builders who need kitchen conversion and construction calculators

Pricing

MJJ Tools is free to use. See the website for details.

FAQ

What is MJJ Tools?

Provides 160+ free online calculators, converters, and developer utilities such as JSON formatters and regex testers, all processed privately in the browser without registration.

How does MJJ Tools work?

Who is MJJ Tools for?

MJJ Tools is designed for a range of users, including: • Software developers who need regex testers, JSON formatters, and cron generators • Students who need AP score, GPA, and grade curve calculators • Home cooks and DIY builders who need kitchen conversion and construction calculators

What can you do with MJJ Tools?

With MJJ Tools you can: • Convert cooking measurements such as grams to tablespoons or Fahrenheit to Celsius for recipes. • Debug regex patterns or decode JWT tokens while building software. • Estimate a mortgage payoff or prorate rent for personal finance decisions.

Is MJJ Tools free?

Yes. MJJ Tools is free to use. See the website for details.