DEV Community: Johin Johny

How to Generate a UUID Online (And When You Should Use One)

Johin Johny — Thu, 19 Feb 2026 18:29:40 +0000

What Is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to identify information in computer systems. It looks like this:


550e8400-e29b-41d4-a716-446655440000

That is 32 hexadecimal digits displayed in five groups separated by hyphens, following the pattern 8-4-4-4-12. The total number of possible UUIDs is 2^128 — roughly 340 undecillion. The odds of generating two identical UUIDs are so low that you can treat them as unique without any coordination between systems.

UUID Versions: v1 vs v4
Not all UUIDs are created the same way.

UUID v1 (Time-Based)
Generated from the current timestamp and the MAC address of the machine. This means:

UUIDs are roughly sortable by creation time
Two UUIDs from the same machine will never collide
The MAC address is embedded, which can be a privacy concern

UUID v4 (Random)
Generated from random or pseudo-random numbers. This is the most commonly used version because:

No information about the machine or time is leaked
Simple to generate — just 122 random bits
Supported by every language and platform

When in doubt, use v4. It is the default in most libraries and the safest choice for general use.

When to Use UUIDs vs Auto-Increment IDs
Auto-increment IDs (1, 2, 3, ...) are simple and small. UUIDs are larger and random. Here is when each makes sense:

Use Auto-Increment IDs When:

You have a single database and never need to merge data
You need compact, human-readable IDs (like order #1042)
Storage efficiency matters (4 bytes vs 16 bytes per ID)

Use UUIDs When:
Distributed systems — multiple services or databases need to generate IDs independently without coordination
Security — you don't want users to guess valid IDs by incrementing (/users/1, /users/2)
Data merging — combining datasets from different sources without ID collisions
Offline-first apps — clients generate IDs before syncing to a server
Public APIs — UUIDs prevent enumeration attacks on your endpoints
Most modern applications use UUIDs for at least some of their identifiers, especially for resources exposed in URLs or APIs.

How to Generate UUIDs With ToolBox
Step 1: Open the UUID Generator
Go to ToolBox UUID Generator. The interface is straightforward — you will see generated UUIDs immediately.

Step 2: Generate UUIDs
Click to generate one or multiple UUIDs at once. Each UUID is a cryptographically random v4 identifier generated entirely in your browser using the Web Crypto API.

Step 3: Copy and Use
Click any UUID to copy it to your clipboard, or copy all of them at once. Use them in your database schemas, API payloads, configuration files, or anywhere you need unique identifiers.

UUIDs in Different Languages
Here is how you generate UUIDs programmatically in common languages:

JavaScript / Node.js


// Node.js (built-in since v14.17)

const { randomUUID } = require('crypto');

console.log(randomUUID());

// Browser

console.log(crypto.randomUUID());

Python


import uuid

print(uuid.uuid4())


import "github.com/google/uuid"

id := uuid.New()

PostgreSQL


SELECT gen_random_uuid();

Common UUID Mistakes
Storing as VARCHAR Instead of a UUID Type
If your database supports a native UUID type (PostgreSQL, MySQL 8+), use it. Storing UUIDs as VARCHAR(36) wastes space and is slower to index.

Using UUIDs as Primary Keys in MySQL with InnoDB
InnoDB stores rows in primary key order. Random UUIDs cause frequent page splits and poor write performance. If you must use UUIDs as primary keys in MySQL, consider UUID v7 (time-ordered) or store them as BINARY(16) with ordered generation.

Assuming UUIDs Are Secret
UUIDs are unique, not secret. Do not use a UUID as an authentication token or password reset link unless combined with other security measures. They are identifiers, not credentials.

Try It Free
Open ToolBox UUID Generator — generate cryptographically random UUIDs instantly in your browser. Free, private, no signup required.

Need to hash those UUIDs? Try the Hash Generator. Building an API that uses UUIDs? Generate mock responses with the API Mock Response Generator.

7 Things Developers Google Every Week (And How to Do Them Faster)

Johin Johny — Thu, 19 Feb 2026 13:58:19 +0000

Every developer has a set of micro-tasks they Google constantly. Format some JSON. Generate a UUID. Check a regex. Convert a timestamp. Each one takes 30 seconds — but the tab-hunting, ad-closing, and

cookie-banner-dismissing adds up.

I built ToolBox to put all of these in one place. 139 free tools, all running client-side in your browser. No signup, no tracking, no limits.

Here are the 7 tasks I used to Google multiple times a week, and how I handle them now.

1."json formatter online"

You get a blob of minified JSON from an API response and need to read it. Every developer has done this hundreds of times.

The problem with most JSON formatters: They upload your data to a server. If you're working with production data, API keys, or customer information, that's a non-starter.

What I do now: Paste it into ToolBox JSON Formatter. It formats, validates, and syntax-highlights instantly. Everything runs in the browser — nothing

leaves your machine.

Bonus: it auto-detects JSON on your clipboard when you visit the page.

2. "regex test online"

Regex is one of those things where the feedback loop matters more than anything. Writing regex in your code, running it, checking the output, tweaking, running again — that's painfully slow.

What I do now: ToolBox Regex Tester shows matches highlighted in real time as you type. No "Run" button. It also shows capture groups, match indices, and

count.

For more complex patterns, the Regex Playground has a library of 35+ common patterns (emails, URLs, IPs, dates) you can load with one click.

*3. "uuid generator"
*
Need a UUID for a database seed, a test fixture, or a config file? You Google it, land on a random site, copy one UUID, and close the tab.

What I do now: ToolBox UUID Generator generates cryptographically random v4 UUIDs using the Web Crypto API. Generate one or bulk-generate dozens. Copy

with a click.

*4. "base64 encode" / "base64 decode"
*
Encoding a JWT payload. Decoding a data URI. Checking what's inside a base64 blob in an email header. This comes up constantly.

What I do now: ToolBox Base64 Encoder/Decoder handles both directions instantly. Paste encoded text → get decoded output. Paste plain text → get base64.

For JWTs specifically, the JWT Decoder splits the token into header, payload, and signature with syntax highlighting.

*5. "diff checker online"
*
Comparing two config files. Checking what changed between two versions of a function. Verifying a copy-paste didn't miss anything.

What I do now: ToolBox Diff Checker shows a side-by-side diff with line numbers, color-coded additions and deletions. It's the most-used tool on the site —
for good reason.

It also works great for verifying that two texts are identical. Paste both sides, and if there's no diff, you know they match exactly (including invisible characters like trailing spaces).

6. "timestamp converter" / "unix timestamp to date"

Every API returns timestamps differently. Unix seconds, milliseconds, ISO 8601. You need to convert between them constantly.

What I do now: ToolBox Timestamp Converter converts between Unix timestamps (seconds and milliseconds), ISO 8601, and human-readable dates. It also
shows the current timestamp live, which is handy when you need "right now" as a Unix timestamp.

7. "password generator"

Setting up a new service, creating test accounts, rotating credentials. You need a strong random password and you need it now.

What I do now: ToolBox Password Generator generates cryptographically strong passwords with configurable length, character sets, and exclusion rules.
It also shows password strength analysis and estimated crack time.

Since it runs client-side, the generated password never touches a server. That matters when you're generating credentials for production systems.

Why client-side matters

Most online tools upload your input to a server, process it, and send back the result. That means your JSON with API keys, your regex test strings with customer data, your passwords — all of it hits

someone else's server.

Every tool on ToolBox runs 100% in your browser. Open DevTools, check the Network tab — you won't see any data being sent. For the few tools that need external APIs (like the Grammar Checker or

Translator), you bring your own API key.

*The full list
*
ToolBox has 139 tools across 7 categories:

Text — Word counter, case converter, Lorem Ipsum, text diff, find & replace
Developer — JSON formatter, regex tester, hash generator, JWT decoder, cron parser
Converter — Base64, color converter, JSON to CSV, timestamp, unit converter
Generator — UUID, password, QR code, color palette, dummy data
Image — Compressor, cropper, EXIF viewer, image effects, device mockups
Web — Meta tag generator, SEO analyzer, DNS lookup, SSL checker, CSP generator
Design — Box shadow, gradient, flexbox, grid, typography scale, neumorphism

Check it out at toolbox-kit.com. Everything's free, no signup required.

What's the task you Google most often? I might have already built a tool for it — drop it in the comments.

I built 130+ free developer tools that don't track you, show ads, or require signup

Johin Johny — Sun, 15 Feb 2026 16:53:12 +0000

I've been a developer for a while now, and one thing has always annoyed me: every time I need to format some JSON, decode a JWT, or generate a password, I end up on a different site. Each one has cookie banners, newsletter popups, ads covering half the screen, and some even want me to create an account just to Base64-encode a string.

So I built ToolBox — a free collection of 130+ browser-based tools for developers and designers. No signup. No tracking. No ads. Everything runs client-side.

🧰 What's in it?
Developer Tools: JSON Formatter, Base64 Encoder/Decoder, JWT Decoder, Regex Tester, Diff Checker, SQL Formatter, Code Formatter (Prettier-powered), Hash Generator, AES Encryption, HTTP Request Builder, and more.

Design Tools: CSS Flexbox/Grid Generators, Box Shadow Builder, Gradient Generator, Color Contrast Checker, CSS Animation Builder, Font Pairing, Glassmorphism & Neumorphism generators.

Converters: JSON to YAML, XML to JSON, CSV to JSON, Markdown to HTML, Color Converter, Unit Converter, Currency Converter, Image Format Converter.

Generators: Password Generator, QR Code, Color Palette, Placeholder Images, Favicon Generator, Meta Tag Generator, Privacy Policy Generator, Dummy Data Generator.

Web & SEO: DNS Lookup, SSL Certificate Checker, Website Speed Test, Broken Link Checker, Open Graph Preview, SEO Analyzer, Redirect Chain Checker.

Image Tools: Image Compressor, Image Cropper, EXIF Data Viewer, PDF Merge & Split, SVG to PNG.

Plus: Cheat sheets for Git, Regex, HTML, CSS, and JavaScript.

⚡ What makes it different?
There are plenty of online tool sites. Here's why I built another one:

100% Client-Side: Your data never leaves your browser. When you paste a JWT token or format sensitive JSON, it's processed locally. Nothing hits a server. (Verify it in the Network tab!).

No Accounts: I don't want your email. You open the tool, use it, and leave.

Works Offline: It's a PWA with a service worker. Once you've visited a tool, it works without internet.

Cmd+K Everything: A command palette lets you search across all 131 tools instantly.

Smart Paste: Paste a JWT anywhere on the site, and it suggests opening the JWT Decoder. Paste JSON, it suggests the JSON Formatter. It auto-detects the content type.

Tool Chainer: Pipe the output of one tool into another. Base64 decode → JSON format → copy. Without opening three tabs.

🛠 The Tech Stack
Next.js (App Router, static generation)

React 19 + TypeScript

Tailwind CSS v4 with dark mode

Umami for privacy-friendly analytics (no cookies)

Sentry for error tracking

Libraries: Prettier, Leaflet (Maps), pdf-lib, and more.

Every page is statically generated at build time. No server-side rendering, no database, no backend. The site scores 100/100 on Lighthouse.

✨ Some features I'm proud of
Split View (Ctrl+Shift+S): Open two tools side by side. Handy when you're converting between formats.

Workspace Scratchpad (Ctrl+.): A multi-tab notepad that slides in from the right to stash text while working.

Snippets Manager (Ctrl+Shift+.): Save frequently used code snippets with syntax highlighting.

Input History: Every tool remembers your last 10 inputs. Click the clock icon to restore any of them.

GitHub Gist Integration: Save any tool output directly to a GitHub Gist.

📊 The Numbers
131 tools across 8 categories
18+ blog posts & 5+ cheat sheets

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$0 to use

🔗 Try it
Site: Toolbox

If you have tool suggestions, there's a request page on the site, I'd love to hear what tools you use most and what's missing!