I built 19 free developer tools because the existing ones are terrible
Source: Dev.to
Introduction
Every developer has the same ritual: you need to format some JSON, so you Google “json formatter online.” The top results are usually cluttered with banner ads, cookie consent popups, newsletter modals, and outdated layouts. You paste your JSON, click format, and it works—but the experience feels dirty.
I got tired of that, so I built JSON Knife – a collection of 19 fast, clean, and free developer tools with no ads, no sign‑ups, and no popups. All tools run entirely in the browser; your data never leaves your machine.
Try them here:
Tool List
| Tool | What it does |
|---|---|
| JSON Formatter | Beautify, minify, syntax highlighting |
| JSON Validator | Find exactly where your JSON is broken |
| JSON Diff | Compare two JSON objects side by side |
| JSON ↔ YAML | Convert between JSON and YAML |
| JSON ↔ CSV | Convert flat JSON arrays to CSV and back |
| JSON ↔ TOML | Convert between JSON and TOML |
| Regex Tester | Live matching with group extraction |
| SQL Formatter | Format and minify SQL with dialect support |
| JWT Decoder | Inspect JWT header and payload |
| Cron Generator | Visual builder with human‑readable explanations |
| Docker Compose Builder | Build docker-compose.yml visually with templates |
| Mermaid Editor | Create diagrams with live preview |
| Git Commands | Searchable reference with workflow templates |
| Base64 | Encode and decode |
| URL Encode | Encode and decode URL strings |
| UUID & Hash | Generate UUIDs and compute SHA hashes |
| Epoch Converter | Unix timestamps ↔ human dates |
| Color Converter | HEX, RGB, HSL, HSB with contrast checker |
| HTML Entities | Encode and decode HTML entities |
Key Benefits
- Zero server calls – all processing happens client‑side.
- Instant feedback – Svelte 5’s reactivity updates results as you type, without debouncing or extra “format” buttons.
- Lightweight – each page loads only the code it needs; the whole site loads in under a second on a cold cache.
- Privacy‑first – no backend, no database, no analytics tracking keystrokes.
My Most‑Used Tools
- Cron Generator – visual builder eliminates guesswork about day‑of‑week indexing and step syntax.
- Docker Compose Builder – templates for common services (Postgres, Redis, Nginx, Node) generate correctly indented YAML.
- JSON Diff – quickly spot added, removed, or changed keys between API responses.
SEO Strategy
Each tool page targets a specific search query (e.g., “JSON formatter online”, “Cron expression generator”). Dedicated meta tags, SEO content blocks, and sitemap entries give every tool its own “net” for organic traffic. The meta description consistently reads “No ads, no popups. Free.” – the most effective copy I’ve written.
Development Process
- First version: a single JSON formatter.
- Iteration: added validator, then YAML converter, and kept expanding.
- Time per tool: 1–3 hours; the Mermaid editor was the most complex, the Base64 encoder the simplest (≈20 minutes).
- Tech stack:
- Framework: SvelteKit with
adapter-static(fully pre‑rendered) - Styling: Tailwind CSS 4
- Hosting: Cloudflare Pages (free tier)
- Backend: None – all client‑side JavaScript
- Framework: SvelteKit with
Build Stats
- Build time: ~2 seconds
- Bundle size: each page loads only its required code
- Total hosting cost: $0/month
Monetization (Optional)
While JSON Knife is free, the bottom of each page includes small cards linking to my paid products:
- SvelteUI Pro – premium Svelte 5 component library
- SvelteShip – SaaS starter template for SvelteKit
- MetaScrape – URL metadata extraction API (free tier available)
These act as a gentle funnel without hard selling.
Future Plans
I’m planning to add more tools based on community demand, such as:
- Markdown preview
- JSON Schema validator
- CIDR/subnet calculator
.envfile editor
If you have a daily‑use tool that’s hidden behind ads or popups, let me know!
Get Started
Explore the full suite at . All tools are free, open‑source, and built with a focus on speed, privacy, and a clean user experience.