I Built 30 Free Browser-Based Linux & DevOps Tools — Here's What I Learned

#linux #devops #webdev #opensource

Every time I needed to calculate a subnet, generate a cron expression, or decode a JWT, I'd end up on some ad-infested site that wanted me to sign up, install an extension, or — worst of all — send my data to their server.

So I built LinuxTools.app — 30 free tools that run entirely in your browser. No sign-up. No tracking. No data leaves your machine.

Here's what I built and what I learned along the way.

What's Inside

The tools are organized into three categories:

🐧 Linux Tools (15)

These are the ones I use daily as a sysadmin:

Chmod Calculator — Visual permission calculator. Toggle rwx checkboxes, see the numeric value update in real-time. Way faster than doing the math in your head.
Cron Expression Generator — Build cron jobs visually with a preview of the next 5 execution times. No more guessing if */5 * * * * means every 5 minutes or every 5th minute.
SSH Config Generator — Build ~/.ssh/config visually. Add hosts, keys, tunnels, and proxy jumps without remembering the syntax.
Nginx Config Generator — Generate configs for reverse proxy, SSL termination, redirects, and more.
Systemd Unit File Builder — Create service files visually instead of copy-pasting from StackOverflow.
UFW / iptables Rule Generator — Build firewall rules without memorizing flags.
Server Hardening Checklist — Step-by-step security checklist with actual commands.

Plus: File Permission Converter, Linux Command Cheat Sheets, Shell Script Library, Vim/Nano shortcuts, Package Manager Comparison, Disk Usage Visualizer, Process Explorer, and Performance Analyzer.

☁️ Cloud & DevOps (5)

Subnet Calculator — CIDR notation, network/broadcast addresses, host ranges
Dockerfile Generator — Pick base image, add packages, expose ports, generate
Kubernetes YAML Generator — Deployments, services, ingress configs
Terraform Snippet Generator — AWS/GCP/Azure resource templates
Cloud Cost Calculator — Estimate costs across providers

🔧 Utilities (9)

Base64 Encoder/Decoder
JSON/YAML/TOML Converter
Regex Tester — Real-time match highlighting
Git Command Builder — Pick what you want to do, get the command
SSL Certificate Checker
UUID Generator — v1/v3/v4/v5 with bulk generation
JSON to .env Converter — AWS Secrets Manager / Vault JSON → dotenv
JWT Encoder/Decoder — Inspect headers, payloads, verify HMAC signatures
Network Tools — DNS lookup, WHOIS, reverse DNS, HTTP headers, and more

🛡️ NetOps — Network Reconnaissance

I also built a NetOps section with a self-hosted API backend:

Traceroute, Ping, MTR
DNS Lookup, Reverse DNS
WHOIS, GeoIP, ASN Lookup
Nmap scan, HTTP Headers, Page Links
Subnet Calculator

All powered by a FastAPI backend in Docker with local MaxMind GeoIP databases — zero external API dependencies.

The Tech Stack

Frontend:  Next.js 15 (static export) + TypeScript + Tailwind CSS
Backend:   Python FastAPI (Docker) — for network tools only
Fonts:     Inter (body) + JetBrains Mono (code) + Bebas Neue (display)
Hosting:   Self-hosted on a VPS behind Cloudflare
Deploy:    rsync + Docker Compose

Why Static Export?

Most tools are pure client-side JavaScript. No server needed for chmod calculations or cron parsing. Static export means:

Fast — HTML served directly by nginx
Cheap — No server-side rendering costs
Private — Data never leaves the browser
Reliable — No backend to go down

The only exception is the NetOps tools (ping, traceroute, nmap) which obviously need a server. Those run in a Docker container with a FastAPI backend.

Lessons Learned

1. Client-side tools are underrated

Most "online tools" unnecessarily send your data to a server. A chmod calculator doesn't need a backend. A JWT decoder doesn't need your token sent over the wire. Running everything client-side is faster, more private, and simpler to deploy.

2. The hardest part is the UI, not the logic

Calculating file permissions is trivial. Making a UI that's intuitive enough that someone can figure it out in 3 seconds — that's the actual challenge.