Everyday developer tools,
without the clutter
Format JSON, test a regex, decode a JWT or generate a UUID in seconds. Every tool runs entirely in your browser, so the data you paste stays on your device.
Formatting & Data
Clean up, validate and compare structured text.Encoding & Decoding
Move data between the formats that browsers, URLs and APIs expect.Generators & Security
IDs, passwords and checksums made with your browser's own cryptography.Text Utilities
Count, convert and tidy everyday writing.Converters
Translate times and colours between formats.No tool matches that search. Suggest one?
Why use MeiMoi?
Private by design
There is no backend that processes your input. Formatting, hashing and decoding all happen with your browser's own JavaScript engine.
Fast on any device
Pages are plain HTML with a few kilobytes of JavaScript. They load quickly on a phone and keep working if your connection drops.
Explained, not just provided
Each tool comes with a short guide covering how it works, common mistakes and when to use something else.
Free, no account
No sign-ups, usage limits or watermarks. Open a page and use it.
Latest from the blog
All articles →How Long Should a Password Be in 2026?
What password entropy means, why length beats complexity, how attackers actually crack passwords, what current NIST guidance says, and practical lengths for different accounts.
UUID v4 vs v7: Which One Should Your Database Use?
Random UUID v4 versus time-ordered UUID v7: how they are built, why v7 makes better primary keys, when v4 is still the right choice, and how they compare to auto-increment IDs.
Unix Timestamps, Time Zones and the Seconds-vs-Milliseconds Bug
How Unix time works, why storing UTC saves you pain, the classic seconds/milliseconds mix-up, daylight saving traps and the year 2038 problem.
About these tools
MeiMoi started as a personal collection of small utilities. Like most developers, we kept searching for "json formatter" or "base64 decode" several times a week and landing on pages full of pop-ups, or worse, pages that quietly send whatever you paste to a server. Pasting an access token or a customer record into a site like that is a real risk.
So we built the tools we wanted: quick to load, honest about what they do, and private by default. Each one is a single static page. When you click Format or Generate, the work is done by your browser, using standard web APIs like JSON.parse, TextEncoder and the Web Crypto API. You can open your browser's developer tools and watch the network tab: no requests are made with your data.
We also try to explain the "why" behind each tool. Knowing the difference between encodeURI and encodeURIComponent, or why Base64 is not encryption, prevents more bugs than any tool can fix. If something is unclear or wrong, or there's a tool you'd like to see, let us know.