I built a toolbox where your data never leaves the browser — 200+ tools, no servers

Like every developer, I have a graveyard of bookmarked "online tools." One site to format JSON, another to generate a password, a third to count words, a fourth to convert a timestamp. Each one slow, ad-heavy, and — the part that always bugged me — quietly posting whatever I paste to some server I know nothing about.

That last bit is the thing most people never think about. You paste an API response into a "free JSON formatter," and you have no idea whether that payload (tokens and all) just got logged on someone's backend. For a quick scratchpad tool, that's a weird amount of trust to hand a stranger.

So I built ToopTools — a collection of 200+ small utilities with one hard rule: everything runs client-side. Your data never leaves your browser.

The one constraint that shaped everything

The rule sounds simple, but it's actually a strong design constraint: if a tool can't run entirely in the browser, it doesn't get built.

That means:

• No backend processing. Formatting, encoding, hashing, converting — all of it happens in JS on your machine.
• No accounts, no database. There's nothing to store, because I never receive your input in the first place.
• Verifiable, not just promised. Open DevTools → Network tab, run any tool, and watch it stay empty. That's the whole pitch, and you can check it yourself instead of taking my word for it.

It's a nice property to be able to say "I literally cannot leak your data, because it never reaches me."

The stack

Nothing exotic, on purpose:

• Next.js for the app and per-tool pages
• Vercel for hosting
• Each tool is a self-contained client component — pure functions doing the actual work
• A personalized workspace where you can pin the tools you use most, so you're not re-searching "json formatter" every single day (this is the part I use the most myself)

Some of the tools devs seem to reach for

• JSON formatter / validator
• Base64 encode / decode
• Password generator
• Hash & UUID generators
• Case converter (camel / snake / kebab / etc.)
• QR code generator
• ...and a long tail of converters and calculators

What I'm still figuring out
A few things I'd genuinely love input on:

1. Discoverability of the workspace. Most people land on a single tool from search and never realize they can build a pinned workspace. How would you surface that without being annoying?
2. Which tools are actually worth adding next? I have a list, but I'd rather build what people reach for than guess.
3. Trust signaling. Is the "open your Network tab and check" framing convincing, or does it need something more concrete (like a visible "runs offline" badge)?

If you've built something similar, or you just have opinions on client-side-everything as an architecture, I'm all ears. And if you want to kick the tires: tooptools.com — no signup, and you can confirm the privacy claim in about ten seconds.

Happy to answer anything about the build in the comments. 👇