25 focused tools · client-side

Small tools for
real development work.

Format JSON, inspect a JWT, test a regex, or check a domain. Inputs stay in your browser.

tools       25
articles    5
runs in     your browser
works       offline after first visit
sign up     never
ads         never
search      ⌘K

01Data & encoding9 tools

json

JSON

Format, validate, minify. Live errors with line and column.

 jwt

JWT

Decode header, payload, claims. Read-only, no verification.

 regex

Regex

Live tester with match highlights and capture groups.

 b64

Base64

Encode and decode. Optional URL-safe variant.

 url

URL encoding

encodeURIComponent and decode, with edge cases visible.

 md

Markdown

Live preview, side-by-side, copy as HTML.

 html

HTML entities

Encode & → & or back; full named-entity table.

 img

Image to Base64

Convert images to data URLs and back.

 yaml

YAML & JSON

Convert both ways. Errors reported with location.

02Generators & hashes4 tools

uuid

UUID

v4 (random) or v7 (time-ordered).

 hash

Hash

MD5, SHA-1, SHA-256, SHA-512. WebCrypto where available.

 lorem

Lorem ipsum

Words, sentences, or paragraphs. Adjustable length.

 pw

Password strength

Entropy, crack time, and warnings.

03Time, color, schedule3 tools

ts

Timestamp

Unix & ISO 8601 & human-readable, multi-timezone.

 color

Color

HEX, RGB, HSL, OKLCH conversion plus WCAG contrast.

 cron

Cron

Build, explain, and preview the next fire times.

04Network & compare3 tools

qr

QR code

Text or URL to SVG and PNG, four EC levels.

 cidr

CIDR / subnet

Network, broadcast, host range, binary view.

 diff

Text diff

Line-by-line LCS, side-by-side view.

05Design & assets2 tools

grad

CSS gradient

Linear or radial, multi-stop, copy CSS.

 fav

Favicon

Text, emoji, or image to all sizes plus manifest.

06Network checks4 tools

dns

DNS lookup

Inspect common DNS records for a domain.

 rdap

WHOIS / RDAP

Check registration dates, status, and nameservers.

 http

HTTP headers

Review response and security headers for a URL.

 tls

TLS certificate

Check certificate issuer, names, and expiry.

07Learn5 articles

read

JWT, explained

Structure, claims, and the four common pitfalls.

 read

UUID v4 vs v7

Why v7 is the right default in 2026.

 read

Regex by example

A working developer's reference, twelve patterns.

 read

CIDR, explained

Masks, subnets, host counts, and IPv6.

 read

Base64, explained

Why 4/3, padding, and the URL-safe variant.

Frequently asked

Is JustKit free?
Yes. Every tool is free, with no signup and no usage limits. Built and run by Auva Labs.
Where does my data go?
Nowhere. Every tool runs entirely in your browser. Your input is never transmitted to any server. (The page itself loads from our CDN, and fonts may load from a font CDN on first visit, but neither receives anything you type.)
Do I need to sign up or log in?
No. There are no accounts. Open the page, use the tool, leave.
Does JustKit work offline?
Yes. After the first visit, the service worker caches the assets so most tools keep working without a connection.
How do the security-related tools work?
SHA hashes use the browser-native WebCrypto API. The JWT decoder only reads a token and does not verify its signature; use a maintained library for application verification.
How do I report a bug or request a tool?
Email [email protected]. We read everything.