Free JSON, Cron and Regex Tools in Your Browser

Pick the job

JSON Format & validate Pretty-print, minify, or confirm a payload before you ship it. Cron Build a schedule Write or decode a cron expression in plain English. Regex Test a pattern Live matches against sample text, with clear empty and error states. Convert JSON → CSV Flatten arrays into a downloadable spreadsheet file. Encode Base64 & URL Encode or decode text locally — UTF-8 safe. Time & IDs Timestamps & UUIDs Unix time ↔ human date, or mint random v4 UUIDs in bulk.

How it works

Open a tool — one page, one job. No account wall.
Paste or type — input stays in this tab; nothing is uploaded to our servers.
Run the action — Format, Convert, Generate, Encode — the primary button does the work.
Copy or download — take the result and leave. Closing the tab drops the text.

Why Fieldkit

No signup

Every tool is usable the moment the page loads. No forced account to format a line of JSON.

Runs in your browser

The JavaScript that formats or parses runs locally on your machine. Offline works after the page has loaded.

One page, one job

Each instrument does exactly one thing well — without burying the action under popups.

Funded by ads, not walls

Display advertising keeps the tools free. No tool's functionality is limited or gated behind ads.

Most "free tool" sites bury a simple conversion under trackers, forced signups, or ten seconds of interstitial ads. Fieldkit does one thing: give you a working instrument, on one page, that runs entirely in your browser. No account, no upload, no rate limit.

All tools

JSON · 001

JSON Formatter & Validator

Paste messy JSON, get it formatted, minified, or validated instantly.

Open tool → CRON · 002

Cron Expression Generator

Build and decode cron schedules in plain English.

Open tool → REGEX · 003

Regex Tester

Test patterns against sample text with live match highlighting.

Open tool → CONVERT · 004

JSON to CSV Converter

Flatten JSON arrays into a downloadable CSV file.

Open tool → ENCODE · 005

Base64 Encode / Decode

Convert text to and from Base64 instantly, with full UTF-8.

Open tool → TIME · 006

Timestamp Converter

Unix timestamp to human-readable date, and back.

Open tool → ID · 007

UUID Generator

Generate random v4 UUIDs in bulk, with format options.

Open tool → URL · 008

URL Encoder / Decoder

Percent-encode text for URLs, or decode it back.

Open tool → COLOR · 009

Color Converter

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

Open tool →

When to use / When not to use

Use Fieldkit for quick, local jobs: pretty-printing a JSON log line, checking a cron string, smoke-testing a regex, flattening a small JSON array to CSV, encoding a string, converting a timestamp, minting a few UUIDs, or checking a color value. Prefer it when you do not want an account and the input can stay in the tab.

Do not use Fieldkit as a substitute for your editor, CI, or production libraries; for multi-megabyte datasets; for secrets you must never put in a browser tab; or when you need server-side history, team sharing, or guaranteed offline packaging. Ads need a network; the instruments themselves run in-page after load.

FAQ

Do I need an account?

No. Every tool works as soon as the page loads. There is no login, no email capture, and no forced signup before Format, Convert, Generate, or Encode.

Is what I paste uploaded?

No. Tools run as static JavaScript in your browser. Text you paste is processed locally and is not transmitted to Fieldkit servers for formatting or conversion. Closing the tab drops the text.

Will the tools work offline?

After the page has loaded, the instruments keep working without a network connection. Ads and any third-party scripts may not. A full refresh without network will not re-download the page assets.

How is the site funded?

Fieldkit is free and supported by display advertising. No tool's functionality is limited or gated behind ads. There is no paywall on Format, Convert, Generate, or Encode.

Which browsers are supported?

Current evergreen browsers (recent Chrome, Firefox, Safari, and Edge) are the target. The tools use ordinary web APIs such as JSON.parse, TextEncoder, and crypto.getRandomValues. Very old browsers without those APIs may fail silently or show incomplete UI.

Which tools are available?

JSON Formatter & Validator, Cron Expression Generator, Regex Tester, JSON to CSV Converter, Base64 Encode/Decode, Timestamp Converter, UUID Generator, URL Encoder/Decoder, and Color Converter. Each lives under /tools/… and is linked from the home page tool grid.

Can I use the output commercially?

Yes. Results you produce with these client-side tools (formatted JSON, cron strings, UUIDs, encoded text, and so on) are yours to use in commercial projects. Fieldkit does not claim ownership of your input or output. The site itself remains under its own branding and is not a white-label product you redistribute as your own hosted service.

What about cookies and ads?

Display ads may set or read cookies and similar storage via Google AdSense and related partners. That is separate from the tool logic, which does not need your paste to leave the tab. Details are in the Privacy Policy. Ad blockers can hide units; the instruments still run.

JSON, cron and regex done — without signup or upload