🥷 ToolNinja — Fast, Free Developer Tools
Free developer tools that run in your browser. No login.
Live at: toolninja.io
What is ToolNinja?
ToolNinja is a free, browser-based developer toolbox. Every tool processes your input locally in
the browser — what you paste into a tool isn't sent to our servers. No accounts required. (A few
tools, like the HTTP Request Builder and the README Badge Generator's live stats, make requests to
the APIs you point them at — that's what those tools do.)
What does involve a server:
- Ask Ninja (AI) — questions you submit, and an image if you attach one, are sent to
Anthropic's API to generate the answer. The paste detection that runs as you type stays in the
browser; we keep only anonymous counts, a short topic label and, when no tool fits, a one-line
summary of the tool you needed — never your question.
- Ratings and comments on tool pages are stored on our server (anonymously — no account, no IP
address; spam checks use a daily-rotating hash).
- Ads and analytics — the site shows Google AdSense ads, uses cookieless Vercel Analytics, and
loads Google Analytics only if you accept analytics cookies.
The privacy policy has the details.
🛠️ Tools (135 total)
Format
JSON Formatter · NDJSON / JSON Lines Formatter & Validator · Markdown Preview · SQL Formatter · HTML Formatter · Word Counter · SVG Optimizer · Image Compressor · Image EXIF Viewer & Remover · GraphQL Query Formatter · XML Formatter · List Sorter & Deduplicator · JavaScript / TypeScript Formatter & Minifier
Encode
Base64 Encoder/Decoder · URL Encoder/Decoder · JWT Decoder · Hash Generator · HTML Entity Encoder · Image to Base64 · Base58 Encoder / Decoder · Base32 Encoder / Decoder · Base62 Encoder / Decoder
Generate
Lorem Ipsum Generator · Password Generator · UUID Generator · ULID Generator · JSON to TypeScript · JSON to Zod Schema Generator · QR Code Generator · QR Code Scanner / Decoder · JWT Generator · Git Command Generator · Markdown Table Generator · Markdown Table of Contents Generator · Meta Tags Generator · Favicon Generator · Fake Data Generator · .gitignore Generator · JSON Schema Generator · Slug Generator · robots.txt Generator · XML Sitemap Generator · Barcode Generator · README Badge Generator · Open Source License Generator · GitHub Actions Workflow Generator · MCP Config Generator & Validator
Convert
Color Converter · Timestamp Converter · Number Base Converter · String Case Converter · JSON ↔ YAML Converter · IP / CIDR Calculator · CIDR Merge & IP Range to CIDR · VLSM Subnet Planner · Docker Run to Compose · Dockerfile Generator · CSV to JSON Converter · XML ↔ JSON Converter · Env File Tool · cURL to Code · URL Parser & Query String Builder · .htaccess to Nginx Converter · Meeting Planner · JSON to Markdown Table · SVG to JSX / React Component · Database Connection String Parser & Builder
Test
Regex Tester · Diff Checker · CRON Expression Tester · HTTP Request Builder · WebSocket Tester · SemVer Calculator & Range Checker · YAML / TOML / JSON Validator · Text Diff · XPath Tester · CSS Selector ↔ XPath Converter · JSON Diff Checker · JSON Patch (RFC 6902) Generator & Applier · IBAN Validator & Generator · Credit Card Test Number Generator · Payment Test Cards · Unified Diff / Patch Generator · UUID Parser · TypeScript 7 Migration Checker · Node.js Type-Stripping Checker · HTTP Header Inspector · CORS Error Debugger · JSONPath Tester · JSON Path Finder · User-Agent String Parser · Structured Output Schema Checker · Node.js 26 Upgrade Checker
Design
CSS Animations · CSS Flexbox Generator · CSS Grid Generator · CSS clamp() / Fluid Typography Calculator · CSS Unit Converter · Aspect Ratio Calculator · SVG Path Visualizer · CSS Custom Properties Auditor · CSS Gradient Generator · Color Palette Generator · Mermaid Diagram Editor · Image Color Palette Extractor · CSS Box Shadow Generator · CSS Specificity Calculator · Placeholder Image Generator · CSS Scrollbar Generator · CSS Scroll Carousel Generator
Security
AES / RSA Encryption · CSP Header Builder & Analyzer · JWT Key Pair Generator · SSH Key Generator · 2FA Live Code & TOTP Generator · HOTP Generator · 2FA Backup Codes Generator · package.json Script Inspector · HTTP Security Headers Checker · JWK ↔ PEM Converter · Secret / API Key Scanner · Password Strength Checker · JWK Thumbprint Calculator · Passkey / WebAuthn Playground · Bcrypt Hash Generator & Verifier · X.509 / PEM Certificate Decoder · SPF, DKIM & DMARC Checker · Google Authenticator Export Decoder
Accessibility
Color Contrast Checker · Color Blindness Simulator
Reference
HTTP Status Codes · Chmod Calculator · AI Token Counter & Cost Estimator · LLM API Cost Calculator · Unicode Explorer
✨ Why ToolNinja?
- Tools run in your browser — your input stays on your machine
- Zero setup — open a tool and start working, no account
- Built for depth — match tables, tree views, char-level diffs, WebCrypto
- Ask Ninja — paste anything to identify it, or ask which tool solves your problem
🏗 Tech Stack
| Layer | Choice |
|---|
| Framework | Next.js 14 (App Router) |
| Language | TypeScript (strict) |
| Styling | Tailwind CSS v3 |
| Fonts | Geist Sans + Geist Mono |
| AI | Anthropic SDK — Claude Haiku for Ask Ninja and comment moderation |
| Storage | Upstash Redis (via the Vercel integration) — ratings, comments, admin settings, rate limits |
| Ads | Google AdSense |
| Analytics | Vercel Analytics & Speed Insights; Google Analytics with consent |
| Alerts | Telegram bot for the admin (reviews, budget, sign-ins) |
| Tests | Vitest |
| Hosting | Vercel |
🚀 Run Locally
git clone https://github.com/aarza056/toolninja.git
cd toolninja
npm install
npm run dev
Open http://localhost:3000. Without environment variables the tools work
as normal; Ask Ninja falls back to local detection and storage uses an in-memory fallback.
Optional .env.local settings:
| Variable | Used for |
|---|
ANTHROPIC_API_KEY | Ask Ninja AI answers and comment moderation |
KV_REST_API_URL, KV_REST_API_TOKEN | Upstash Redis (set automatically by the Vercel integration) |
ADMIN_PASSWORD, ADMIN_SESSION_SECRET | /admin sign-in |
TELEGRAM_BOT_TOKEN | Admin alerts |
VERCEL_API_TOKEN (+ VERCEL_TEAM_ID for team projects, VERCEL_ANALYTICS_PROJECT if not toolninja) | Admin → Analytics and the Telegram /visitors commands |
NEXT_PUBLIC_GA_ID | Google Analytics (consent-gated) |
Checks: npm test, npx tsc --noEmit, npx next lint — CI runs all three on every push and pull request.
➕ Adding a New Tool
- Add an entry to
lib/tools.ts (slug, name, description, icon, category, keywords).
- Create
app/tools/<slug>/page.tsx — server component with generateToolMetadata("<slug>"),
<ToolJsonLd slug="<slug>" /> and <ToolSeoSection slug="<slug>" /> (copy an existing tool page).
- Create
app/tools/<slug>/<Name>Client.tsx ("use client" — the interactive tool). Put pure
logic in lib/<name>.ts and add a test for it in tests/.
- Add a hand-written title and description to
toolMeta in lib/metadata.ts.
- Add SEO content to
lib/tool-content.ts (about, useCases, tips, faq).
- Optional: add the slug to
LATEST_TOOL_SLUGS in lib/tools.ts (NEW badges, What's New popup)
and a release entry to lib/changelog.ts.
- Run
npm run readme:tools to refresh the tool list above.
The sitemap, /tools, the category hubs, /llms.txt and the search palette all read
lib/tools.ts, so they pick the new tool up automatically. /admin → Content health flags
anything missing.
📁 Project Structure
app/
layout.tsx → Root layout (sidebar, banner, Ask Ninja, analytics)
page.tsx → Homepage
tools/<slug>/ → Individual tool pages
ask/ → Ask Ninja page
admin/ → Owner dashboard (password + 2FA)
api/ → Ask Ninja, reviews, admin and Telegram endpoints
blog/ → Blog articles
sitemap.ts → Sitemap, generated from the registries
llms.txt/ → /llms.txt, generated from the tool registry
components/ → Shared UI (Sidebar, ToolLayout, CommandPalette, assistant/, admin/, reviews/)
lib/
tools.ts → Master tool registry
tool-content.ts → SEO content per tool
metadata.ts → Titles, descriptions, JSON-LD
kv.ts → Upstash Redis wrapper with an in-memory dev fallback
tests/ → Vitest unit tests for lib/
📄 License
MIT — free to use, modify and distribute.
🤝 Contributing
PRs welcome! Found a bug? Open an issue.
Want to add a tool? Follow the "Adding a New Tool" guide above.
Built with ❤️ and caffeine by @aarza056
