Developer

15 Free Online Developer Tools You'll Actually Use

6 min read Updated 30 June 2026

Every developer keeps a scratch tab open for the small jobs: pretty-printing a JSON blob, decoding a JWT to see why auth is failing, double-checking a regex before it ships. The problem is that a lot of those "quick" online developer tools want an account, throw a paywall at you after a few uses, or quietly upload whatever you paste to a server you've never heard of. That's a bad trade when the thing you pasted is a production token or an internal payload.

Tooldrop's developer tools at /dev take the opposite approach. They're free with no sign-up and no usage limits, and most of them run entirely in your browser — your data never gets uploaded. Below are the ones you'll reach for most, what each does, and when it's the right tool to grab.

The tools

1JSON Formatter (/dev/json-formatter) — Beautifies, minifies and validates JSON with friendly error messages, the first thing to reach for when an API response is an unreadable single line or won't parse.
2JSON to CSV Converter (/dev/json-to-csv) — Turns a JSON array of objects into RFC 4180-compliant CSV (and back again), perfect for dropping API data into Excel or Google Sheets without writing a script.
3Base64 Encode / Decode (/dev/base64) — Encodes text to Base64 or decodes it back, UTF-8 safe so emoji and accents survive, handy for data URIs, config values and quick payload inspection.
4URL Encoder / Decoder (/dev/url-encoder) — Percent-encodes or decodes URLs and query strings with both component and full-URI modes, for when a parameter is breaking your links or you need to read an encoded redirect.
5JWT Decoder (/dev/jwt-decoder) — Decodes a JSON Web Token's header and payload so you can inspect claims and expiry while debugging auth, with everything decoded locally so the token never leaves your machine.
6Regex Tester (/dev/regex-tester) — Tests JavaScript regular expressions against sample text with live match counts, capture groups and clear error messages, so you can nail a pattern before pasting it into code.
7Hash Generator (/dev/hash-generator) & UUID Generator (/dev/uuid-generator) — Generate SHA-1/256/384/512 hashes for checksums and fingerprints, or one-click cryptographically random version-4 UUIDs for test data and new records, all via the Web Crypto API.
8Number Base Converter (/dev/number-base-converter) & Timestamp Converter (/dev/timestamp-converter) — Convert numbers between binary, octal, decimal and hex, and turn Unix timestamps (seconds or milliseconds) into readable UTC and local dates and back — the quick answers for a bitmask or an epoch in a log.
9Cron Expression Helper (/dev/cron-expression) — Translates a 5-field cron expression into a plain-English sentence with handy presets, so you can confirm a schedule means what you think before it hits production.
10Color Converter (/dev/color-converter) — Converts colors between HEX, RGB and HSL with a picker and per-format copy buttons, for translating a design value into whatever your stylesheet needs.
11CSS Gradient Generator (/dev/gradient-generator) & CSS Box Shadow Generator (/dev/box-shadow-generator) — Build linear and radial gradients or dial in box-shadow offset, blur, spread and inset with a live preview, then copy ready-to-paste CSS for backgrounds, buttons, cards and modals.
12HTML Entity Encoder & Decoder (/dev/html-entities) & Color Contrast Checker (/dev/contrast-checker) — Escape unsafe characters (& < > " ') into entities or reverse them, and check the WCAG contrast ratio between two colors with AA/AAA pass-fail — two fast safety checks for clean markup and accessible UI.

Try it now — it's free

Runs in your browser. No upload, no sign-up.

Browse the tools

What makes these online developer tools worth bookmarking

The pitch for any utility site is convenience, but convenience usually comes with strings attached. Tooldrop's developer tools cut those strings in three ways.

First, they're genuinely free: no sign-up, no account wall, and no daily or character limits to bump into halfway through a task. Open the page and use it.

Second, most of them run privately in your browser. Tools like the JWT Decoder, Regex Tester, Hash Generator and JSON Formatter do all their work in client-side JavaScript, which means the token, log line or payload you paste never gets uploaded to a server. That's the difference between safely inspecting a production JWT and leaking it. Many of these pages even keep working offline once they've loaded.

Third, they're built to be instant. Results update as you type or paste, there's a one-click copy on the outputs, and there's nothing to install or configure.

How to pick the right tool for the job

A quick mental map helps. For data wrangling, the JSON Formatter, JSON to CSV Converter, Base64 and URL Encoder cover the bulk of everyday parsing, escaping and exporting.

For debugging and security work, reach for the JWT Decoder when auth misbehaves, the Regex Tester before you commit a pattern, and the Hash Generator or UUID Generator when you need fingerprints or fresh identifiers.

For the in-between conversions that always seem to come up — an epoch timestamp in a log, a hex value, a cron line nobody can read — the Timestamp Converter, Number Base Converter and Cron Expression Helper each answer one question fast.

And for front-end polish, the Color Converter, CSS Gradient Generator, CSS Box Shadow Generator, HTML Entity tool and Color Contrast Checker turn fiddly CSS and accessibility checks into a copy-paste. The whole set lives under /dev, so it's worth bookmarking that one page.

Frequently asked questions

Are these developer tools really free with no sign-up?

Yes. Every tool under /dev is free to use with no account required and no daily or character limits. You open the page and start working — there's nothing to install and no paywall waiting after a few uses.

Is my data uploaded when I use the JWT decoder or other tools?

No, not for the in-browser tools. Utilities like the JWT Decoder, Regex Tester, JSON Formatter, Base64 and Hash Generator do all their processing locally in your browser using client-side JavaScript, so your tokens, payloads and text never leave your device. That makes them safe for production tokens and internal data, and many keep working even offline once loaded.

Which developer tool should I use to debug a failing login?

Start with the JWT Decoder at /dev/jwt-decoder to inspect the token's header and payload — check the claims and the expiry first. If the issue is in how a value was encoded, the Base64 and URL Encoder tools help you read it, and the JSON Formatter makes any embedded JSON readable.

Do the CSS tools give me code I can paste straight into a stylesheet?

Yes. The CSS Gradient Generator and CSS Box Shadow Generator both show a live preview and output a ready-to-paste declaration with one-click copy, while the Color Converter gives you HEX, RGB and HSL values to drop in wherever your stylesheet needs them.