DevToolBox
Developer tools that make zero network calls. Verifiable.
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DevToolBox - Developer tools that make zero network calls. Verifiable.

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Most online developer tools have a dirty secret: they send your pasted data to servers. Analytics endpoints, "improvement" APIs, or just... somewhere. DevToolBox is different. Every tool runs 100% in your browser. Not "we promise" — verifiably. Open your Network tab while using any tool. Nothing fires.

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Maker here! The origin story: I caught a popular JSON formatter POSTing my pasted content to a third-party analytics endpoint. After that, I decided to build my own tools where I could *verify* that data stays local. The architecture is simple: pure JavaScript for all computations, no backend, no API calls. The hosting is static files on a CDN. Even if I wanted to steal your data, the code literally has no mechanism to send it anywhere. **7 tools at launch:** • JSON Formatter & Validator • Regex Tester (real-time highlighting) • Base64 Encoder/Decoder (UTF-8 aware) • JWT Decoder (expiry checker) • Hash Generator (MD5 → SHA-512) • URL Encoder/Decoder • Color Converter (HEX/RGB/HSL) **Why it's different:** • Zero network calls (verify in DevTools) • Installable as a PWA (works offline) • No signup, no account, no tracking • Sub-90KB per page load • $0/month to run Next up: Cron Expression Builder, Timestamp Converter, and a JSON Diff tool. Voting on what comes first in the comments!

How does this hold up for the heavier tools like JSON-to-cSV converters with massive datasets, or does performance start to dip once you get past a few MB?

Checked the Network tab while running a base64 decode and a JSON formatter, and yeah, nothing fired. Love seeing the privacy promise actually hold up under inspection.

The verifiable part is what sold me—actually opening the Network tab and seeing zero requests is such a clean way to earn trust instead of just asking for it.

how do you keep tools updated with new web APIs without some kind of background sync, or is it all manual bumps when something breaks?

The "open your Network tab" proof is such a simple move and it does more for trust than any marketing copy could. Love seeing tools that respect the developer using them.