Developer tools that just work

Format and validate JSON & XML, compare two documents, convert Unix timestamps across time zones, decode JWTs, encode Base64 and more. Every tool runs entirely in your browser — nothing is uploaded.

100% client-sideNo sign-upFree & ad-lightWorks offline

Formatters

{ }

JSON Formatter

Pretty-print, minify, sort and validate JSON with clear, line-numbered error messages.

</>

XML Formatter

Indent, minify and check XML documents — including SOAP, RSS, SVG and config files.

Diff & Compare

≠

JSON Diff

A git-style unified diff of two JSON documents, pretty-printed and optionally key-sorted first.

≠

XML Diff

A git-style unified diff of two XML documents after both are re-indented consistently.

Converters

🕑

Epoch Converter

Convert between Unix time (seconds or milliseconds) and human dates in any time zone.

Encoders & Decoders

b64

Base64 Encode / Decode

Encode text to Base64 and decode it back, with full Unicode and URL-safe support.

URL Encode / Decode

Percent-encode and decode URLs, query strings and individual components.

JWT

JWT Decoder

Decode a JWT's header and payload and check expiry — without sending it anywhere.

Generators

UUID Generator

Generate cryptographically-random UUIDv4 or sortable UUIDv7 identifiers in bulk.

Hash Generator

Compute cryptographic hashes of text in MD5, SHA-1, SHA-256 and SHA-512.

Web & Network

((•))

Network Inspector

Open any site through a proxy and watch the API calls it makes — filter them and copy any request as cURL, right from your phone.

curl Runner

Paste a curl command, run it from a server, and see the status, headers and response body — with the JSON pretty-printed.

Database

Postgres Console

Connect to a PostgreSQL database, browse tables and run SQL from a self-hosted console.

MySQL Console

Connect to a MySQL database, browse tables and run SQL from a self-hosted console.

Kafka Console

List Kafka topics and stream messages live from a self-hosted console.

MQTT Console

Subscribe to MQTT topics and publish messages from a self-hosted console.

Why another set of online dev tools?

Most “format my JSON” sites bury a tiny textarea under trackers, pop-ups and full-screen ads, and quietly send your data to a server. DevToolbox is the opposite: each tool is a single fast page that does one job well, keeps your input on your machine, and stays readable on a phone.

Everything runs locally

Parsing, formatting, diffing, hashing and encoding all happen in JavaScript in your browser tab. You can open the network panel and confirm there are no requests carrying your data. That makes these tools safe for API responses, access tokens and config files.

Built for real workflows

Clear syntax errors with line numbers, structural diffs that ignore key order, time-zone-aware timestamp conversion, and copy/download on every result. Start with the JSON formatter, the epoch converter or the JWT decoder.