I'm a solo developer from Seoul, and over the past few months I built ClickVolt — a URL safety scanner. But the tools I ended up using the most are the 3 free developer tools I added along the way.
All of them are 100% free, no signup required, no usage limits.
1. Repo vs Repo — GitHub Repository Comparison
Ever struggled to choose between two similar libraries? This tool lets you compare any two GitHub repos side by side.
What it shows:
- Stars, forks, open issues, watchers
- Primary language, license
- Latest release version and date
- Average weekly commits (4-week and 12-week)
- 52-week commit activity chart
I pre-loaded popular matchups like React vs Vue, Next.js vs Remix, Express vs Fastify, Prisma vs Drizzle ORM, and more.
Why I built it: I kept opening two GitHub tabs and manually comparing numbers. Figured I'd automate it.
2. Repo Radar — Open Source Tool Explorer
Browse popular open source tools across 20 categories: Frontend, Backend, Fullstack, CSS, Auth, ORM, API, Testing, UI Components, State Management, Deployment, AI/ML, and more.
Each category shows 5-15 popular repos ranked by stars, with one-click comparison.
3. Deploy Checker — Production Readiness Audit
→ clickvolt.app/tools/deploy-check
Enter any URL and get a readiness check across 4 categories:
- Security: SSL/HTTPS, security headers (CSP, HSTS, etc.)
- SEO: Title, meta description, heading structure
- Social: Open Graph tags, Twitter Card
- Performance: Response time, page size, compression, caching
I use this before every deployment to catch missing headers or broken OG tags.
Tech Stack
- Framework: Next.js 16 (App Router)
- Language: TypeScript
- Styling: Tailwind CSS v4 + shadcn/ui
- Database: Supabase (PostgreSQL)
- AI: Claude API (for URL scanner's page summaries)
- Hosting: Vercel
The Main Product
The core product is a URL safety scanner — paste any link, get a safety score (0-100), AI summary of what the page does, and a wrapped safe link you can share. Free: 5 scans/day.
Lesson learned: Free tools that solve small, everyday problems are the best marketing for your main product.
I'd love feedback — which tool do you find most useful? Any features you'd want added?
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