Practical Tools
for Developers & Engineers

JSON formatters, regex testers, Base64 encoders for frontend devs.
Cloud cost calculators, GPU estimators, SRE tools for infrastructure teams.

All free. All client-side. No signup. No tracking. Just tools that work.

All Tools

91 Free Tools for Developers & Engineers

Privacy-first browser tools for everyday dev tasks. No signup. No tracking. All client-side.

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Research Briefings

Latest Research

Field-tested engineering investigations — the tax behind every cloud bill, the math behind every outage.

Show 11 More Briefings (Jul 1–26)
2026-07-02jslet Research

UUID v4 Collision Probability at Scale

2.71 quintillion UUIDs for a 50% collision chance. The math says never. Every documented production collision traces back to a bad entropy source.

Why Engineers Use jslet

Built by Engineers, for Engineers

We're the people who get paged at 3 AM. These are the calculators we reach for ourselves — research-backed, client-side, zero barrier to entry.

🔒100% Client-Side

All calculations run in your browser. No data ever leaves your machine. No server-side processing, no logs, no tracking.

🔬Research-Backed Models

Every formula is documented and sourced. We cite our data — Imperva, Cloudflare, Akamai, IEEE, and academic papers.

Zero Barrier to Entry

No registration. No email wall. No pricing page. Just tools that work the moment you land.

🛠️Built by Engineers

We're the people who get paged at 3 AM. These are the calculators we reach for ourselves.

Napkin Math That Survives Production

Take Your Engineering to the Next Level

51 calculators encoding the back-of-the-envelope heuristics we use to avoid provisioning disasters — GPU OOMs, egress billing shocks, RAID rebuild windows that exceed MTTDL.