Free Developer Tools — JSON, Base64, JWT & More

Lightning-fast utilities for JSON, Base64, JWT, regex, hashes and more. Every tool runs in your browser — your data never leaves your device.

100% Private Instant Works on Mobile Always Free

JSON & Data

JSON Formatter

Format, validate, minify and inspect JSON instantly in your browser.

YAML ↔ JSON

Convert between YAML and JSON with a single click.

CSV to JSON

Convert CSV/TSV data into JSON with header detection.

JSON to Types

Generate TypeScript, Go, Python, Rust and Java types from JSON.

Encoding & Hashing

Base64 Encode/Decode

Encode or decode Base64 text and files with auto-detection.

URL Encoder/Decoder

Encode, decode and parse URLs with a built-in query parameter editor.

Hash Generator

Generate MD5, SHA-1, SHA-256, SHA-384, SHA-512 hashes from text or files.

HTML Entity Encode/Decode

Encode and decode HTML entities — named, numeric, and hex.

Auth, Certs & Keys

JWT Decoder

Decode and inspect JWTs — header, payload, claims and expiry.

TLS Certificate Decoder

Decode PEM certificates locally — issuer, SANs, validity, fingerprints.

JWK ↔ PEM Converter

Convert RSA and EC keys between JWK and PEM, public or private.

Text & Code

Regex Tester

Test and debug regular expressions with real-time match highlighting.

Diff Checker

Compare two text blocks and see line and word differences.

CSS/JS Minifier

Minify CSS and JavaScript locally with size savings reported.

SQL Formatter

Format SQL for any major dialect with proper indentation.

Markdown Preview

Preview Markdown side-by-side with rendered HTML and GFM support.

Generators & Time

UUID Generator

Generate UUID v4 / v7 / GUIDs in bulk with one click.

Unix Timestamp Converter

Convert between Unix epoch timestamps and human-readable dates.

Cron Expression Generator

Build and decode cron expressions with next-run previews.

Lorem Ipsum Generator

Generate Lorem Ipsum placeholder text by words, sentences or paragraphs.

Timezone Converter

Compare a time across many timezones at once — IANA-aware, DST-correct.

Password Generator

Generate secure passwords or EFF-wordlist passphrases. Crypto-secure, client-side.

Network

HAR File Analyzer

Analyze HAR files with a waterfall, slowest requests and domain breakdown.

DNS Lookup

Look up A, AAAA, MX, TXT, NS, CAA and more — via DNS-over-HTTPS.

What's My IP

Public IP, country, and everything your browser exposes — one glance.

Reverse DNS Lookup

Look up PTR records for IPv4 / IPv6 with FCrDNS verification. Bulk mode supported.

Design & AI

Color Converter

Convert colors between HEX, RGB, HSL and HSV with a live preview.

LLM Token Counter

Count tokens and compare costs across Claude, GPT, Llama and Gemini.

WCAG Contrast Checker

Check color contrast for WCAG AA & AAA accessibility compliance.

Private by design

Every tool here runs entirely in your browser. Your data is never uploaded, stored or transmitted to our servers. That means faster results — and total privacy.

Built for developers

Whether you're debugging an API response, decoding a JWT, hashing a file or testing a regex, XpressDevTools gives you the right tool without sign-ups, ads in the workflow, or hidden limits.

Need image tools?

Check out XpressImgTools — our sister site for compressing, resizing, cropping and converting images.