Developer Tools

22 utilities for the everyday coding workflow — encoders, generators, decoders, formatters, hashing, regex testing, mock data, and more.

The dev utilities you don't want to install for

Every developer has a personal collection of "I just need to encode this base64 once" moments. You're debugging an API response that includes a JWT and you want to see what's inside it. You need to URL-encode a string before pasting it into a query parameter. You want to generate a UUID without opening a Python REPL. You want to test whether a regex matches what you think it matches. You want a few dozen rows of fake user data to seed a test. These are micro-tasks that interrupt your real work and aren't worth installing or configuring a CLI tool for.

The developer tools here are designed for these moments. Each one is a single page with input on top, output on bottom, and a button in the middle. They use the browser's native APIs where possible (Web Crypto for hashing, the JavaScript regex engine for matching, atob/btoa for base64) and pure-JS libraries where the browser doesn't have the operation natively. Nothing requires server-side processing; nothing sends your input anywhere. Open DevTools and watch the network panel — only static asset loads, never your data.

The set covers the common cases: URL Encode/Decode for query string manipulation, Base64 Encode/Decode for sending binary through text, JWT Decoder for inspecting tokens, Regex Tester for validating patterns against test strings, Hash Generator for SHA-1/256/512 of text, File Hash Verifier for checksumming downloaded files, UUID Generator for v4 random UUIDs, Password Generator for strong random passwords with configurable composition, Timestamp Converter for Unix ↔ ISO 8601, Number Base Converter for 2/8/10/16, SQL/XML/YAML Formatter for the respective formats, Data Format Converter for JSON↔YAML↔TOML↔XML round-trips, Mock Data Generator for realistic test data via faker.js, Cron Expression Builder for cron strings with plain-English descriptions, JSON Diff for semantic structural comparison, and Data URL Encoder for inline file embedding.

For text-shape transformations that aren't strictly developer-only (case conversion, slug generation, find/replace), see text tools. For CSS-specific builders, see design tools.

All developer tools

Data URL Encoder

Convert any file to a data: URL and decode back to a file

File Hash Verifier

Compute MD5/SHA hashes of any file and verify against an expected value

ZIP Compress / Extract

Bundle files into a ZIP or extract files from a ZIP — both directions in your browser

URL Encoder/Decoder

Percent-encode or decode URLs and query strings

HTML Entity Encoder/Decoder

Escape or unescape HTML entities like &, <, >

Password Generator

Generate cryptographically strong random passwords

Unix Timestamp Converter

Convert between Unix timestamps, ISO 8601 dates, and human-readable times

Number Base Converter

Convert numbers between binary, octal, decimal, hex, and any base 2–36

Regex Tester

Test JavaScript regular expressions against sample input with live match highlighting

JWT Decoder

Decode and inspect JSON Web Tokens (header, payload, signature)

SQL Formatter

Pretty-print SQL queries for PostgreSQL, MySQL, SQLite, MS SQL, and more

XML Formatter

Format, indent, and minify XML documents

YAML Formatter

Validate, format, and convert YAML to JSON

JSON ↔ YAML ↔ TOML ↔ XML Converter

Convert structured data between JSON, YAML, TOML, and XML

HTML / CSS / JS Beautifier & Minifier

Beautify or minify HTML, CSS, and JavaScript source

Text Diff

Compare two text blocks side by side with line, word, or character resolution

JSON Diff

Structural diff of two JSON documents — added, removed, and changed paths

Mock Data Generator

Generate realistic fake data (names, emails, addresses, dates, lorem) as JSON or CSV

Cron Expression Builder

Translate cron expressions to plain English and preview next fire times

HMAC Generator

Compute HMAC-SHA1/256/384/512 from a message and secret key. Verify webhook signatures.

Timezone Converter

Convert a wall-clock time between any IANA timezones with DST handled correctly

File Type Detector

Identify a file from its magic bytes — catch mislabeled extensions

Frequently asked questions

Why use these instead of CLI tools or VS Code extensions?

Three reasons. First, these work in any browser — useful on a borrowed machine, a Chromebook, or anywhere you don't want to install software. Second, the input/output is in a textarea you can copy from, which is sometimes more convenient than piping through a CLI tool. Third, they're zero-config — no terminal, no extension installation, no setup. For one-off operations during a debugging session, that matters more than you'd expect.

Is my data safe when I paste JWTs or sensitive strings?

Yes. All operations are JavaScript functions running in your browser. There are no server-side endpoints to leak the data. The JWT Decoder, in particular, never sends the token anywhere — it base64-decodes the header and payload locally. Verify in DevTools by watching the Network panel: paste a token, click Decode, and you'll see zero outgoing requests.

How accurate is the Regex Tester?

It uses the browser's native JavaScript regex engine — the same one your code uses. Any regex you test here will behave identically in JS at runtime. For other languages (PCRE in PHP, Python's re module, Go's RE2), the syntax mostly overlaps but has differences — JavaScript regex doesn't support possessive quantifiers, recursive patterns, or some Unicode property escapes. If you're writing a regex for a non-JS context, double-check the syntax against that language's docs.

What does the Hash Generator support?

Text input → SHA-1, SHA-256, SHA-384, SHA-512 using the browser's native Web Crypto API. MD5 isn't there because Web Crypto omits MD5 (it's considered cryptographically broken). For file hashing — including MD5 for downloaded installer verification — use the File Hash Verifier instead.

What's the difference between Hash Generator and File Hash Verifier?

Hash Generator hashes a text string you paste in. File Hash Verifier hashes a file you drop in. Different inputs, different use cases: the text version is for hashing API tokens, passwords (do not actually hash passwords for storage in client-side JS — use server-side bcrypt or argon2), or short strings; the file version is for verifying downloads against published checksums.

Does the JWT Decoder verify signatures?

No, and we say so on the tool page. Decoding and verifying are different operations. Decoding just base64-decodes the header and payload — useful for inspecting what a token claims. Verifying requires the public key and the original signature algorithm, neither of which is in the JWT itself. For verification, use a server-side library that has the public key.