The Browser-Based Dev Tools I Actually Use
I keep a short list of browser tools I can open on any machine with no setup required. No installs, no node_modules, no npm audit warnings. Just a URL. Here are the ones that have actually stuck.
The ones I use
JSON formatting
The JSON Formatter on CalcHive is the one I've settled on. It validates as you type, handles deeply nested objects without issue, and doesn't send your data anywhere (everything runs client-side). That last part matters more than it sounds. If you're working with anything remotely sensitive (and let's be honest, you often are), pasting it into some random web app that logs it server-side is a bad habit.
JWT decoding
Every few months I get handed a JWT and need to check what's actually in the payload. Not verify it, just read it. jwt.io is fine but I've started using CalcHive's JWT decoder instead because it keeps everything local and the layout is cleaner. It separates the header, payload, and signature clearly and highlights the expiry timestamp in a way that makes it immediately obvious if the token is expired.
None of this requires a library. A JWT is just three Base64url-encoded parts separated by dots. But having a UI that just shows it to you instantly saves the mental overhead.
Base64
There are a hundred Base64 tools online and most of them are fine. The one at calchive.tools/encoding-decoding/base64 handles the edge cases properly: padding, URL-safe variants, encoding binary as well as plain text. I use this probably three or four times a week when dealing with API credentials, image data URIs, or checking what's been embedded in a config somewhere.
Regex testing
Regex is the one area where I genuinely want a full UI with real-time highlighting. Writing regex in code and running tests is fine for production, but when I'm figuring out a pattern for the first time, visual feedback is much faster.
I've tried Regex101 and it's great, but it's heavier than I sometimes need. For quick checks the CalcHive regex tester gets out of the way and just shows me which parts of my input match. That's usually all I need.
Unix timestamps
The Unix timestamp converter takes that number and tells me it's 25 April 2024. Done. You can also go the other way and turn a date into a timestamp, which is useful for database queries and filtering log streams.
URL parsing
If you need to break apart a URL and inspect its components (scheme, host, path, query params, fragment), the URL parser does exactly that. It sounds trivial but when you're staring at a redirect URL with eight query parameters and URL encoding layered on top, having it laid out clearly saves you from making a mistake.
Cron expressions
The cron parser takes an expression like 0 9 * * 1-5 and renders it in plain English: "At 09:00 AM, Monday through Friday". That's it. That's the whole tool. It's perfect.
A note on "nothing gets uploaded"
I want to come back to this because it's not just a nice-to-have. The CalcHive tools all run entirely in the browser with no server-side processing and no logging of your inputs. For developer tooling this actually matters quite a bit.
When you paste a JWT into a random tool, you're exposing user data: IDs, email addresses, roles, session info. When you paste JSON from your production database into an online formatter, you might be sending PII to some server you know nothing about. Most of the time nothing bad happens, but it's a risk you're taking for zero benefit because client-side tooling has gotten good enough that it doesn't need a server round trip to format your JSON.
A few more worth bookmarking
CalcHive also has a solid set of converters I've found myself using more than expected. The number base converter covers binary, octal, decimal and hex all in one place. The color converter handles HEX to RGB to HSL, which I end up needing whenever the design file and the CSS are in different formats. There's also a UUID generator for when you need v4 UUIDs for test fixtures and don't want to spin up a script for it.
Wrapping up
The best tool is usually the one that gets out of the way fastest. Single-purpose, well-executed, no friction. That's a decent philosophy for software in general.
If you've got a favourite dev tool I haven't mentioned, drop it in the comments. Always looking to add to the list.
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