📋 Awesome Developer Tools
A curated list of 51 free, open-source developer tools on korpo.pro. No ads, no signup, no tracking. Just tools that work.
📧 Email & DNS
🌐 DNS Lookup
A, AAAA, MX, NS, TXT, CNAME, SOA records 📊 Email Health Report
MX/SPF/DKIM/DMARC audit with score 📧 Spam Score Checker
15+ spam signals analyzed 📡 Email Header Analyzer
Parse and explain all email headers 🛡️ DMARC Record Generator
Generate DMARC DNS records 📋 DMARC Report Parser
Parse XML aggregate reports 🔄 DNS Propagation Checker
Check DNS across global resolvers ↩️ Reverse DNS Lookup
PTR + forward-confirm check 🧪 Email Tester
Quick email deliverability test
A, AAAA, MX, NS, TXT, CNAME, SOA records 📊 Email Health Report
MX/SPF/DKIM/DMARC audit with score 📧 Spam Score Checker
15+ spam signals analyzed 📡 Email Header Analyzer
Parse and explain all email headers 🛡️ DMARC Record Generator
Generate DMARC DNS records 📋 DMARC Report Parser
Parse XML aggregate reports 🔄 DNS Propagation Checker
Check DNS across global resolvers ↩️ Reverse DNS Lookup
PTR + forward-confirm check 🧪 Email Tester
Quick email deliverability test
🌐 Web & SEO
🔍 SEO Meta Tag Analyzer
Title, description, OG tags, robots 📝 WHOIS Domain Lookup
Registrar, expiry, nameservers 🔒 SSL Certificate Checker
Expiry, issuer, SAN, chain validation 📡 HTTP Headers Checker
Security headers, CORS, caching 📊 HTTP Status Checker
Bulk URL status code checker 🔗 Redirect Chain Checker
Follow 301/302 hops, detect loops 🖼️ Meta Tag Preview
Preview OG cards + Twitter cards 🔗 Backlink Checker
Check who links to a URL 📍 IP Address Lookup
GeoIP, ISP, hostname, abuse contact 🛡️ IP Reputation Checker
Blacklist + abuse score
Title, description, OG tags, robots 📝 WHOIS Domain Lookup
Registrar, expiry, nameservers 🔒 SSL Certificate Checker
Expiry, issuer, SAN, chain validation 📡 HTTP Headers Checker
Security headers, CORS, caching 📊 HTTP Status Checker
Bulk URL status code checker 🔗 Redirect Chain Checker
Follow 301/302 hops, detect loops 🖼️ Meta Tag Preview
Preview OG cards + Twitter cards 🔗 Backlink Checker
Check who links to a URL 📍 IP Address Lookup
GeoIP, ISP, hostname, abuse contact 🛡️ IP Reputation Checker
Blacklist + abuse score
🛠️ Developer Utilities
📋 JSON Formatter
Format, validate, minify JSON 🔤 Base64 Encoder/Decoder
Encode and decode Base64 🔗 URL Encoder/Decoder
URL encode and decode text 🔐 Hash Generator
MD5, SHA-1, SHA-256, SHA-512 🧮 Subnet Calculator
CIDR, netmask, IP range 🔑 SSL Certificate Generator
Generate self-signed certs 📦 CSS/JS Minifier
Minify CSS and JavaScript 🖼️ Image to Base64
Convert images to Base64 data URIs 📝 Markdown to HTML
Convert Markdown to HTML 📖 Swagger Generator
Generate OpenAPI specs
Format, validate, minify JSON 🔤 Base64 Encoder/Decoder
Encode and decode Base64 🔗 URL Encoder/Decoder
URL encode and decode text 🔐 Hash Generator
MD5, SHA-1, SHA-256, SHA-512 🧮 Subnet Calculator
CIDR, netmask, IP range 🔑 SSL Certificate Generator
Generate self-signed certs 📦 CSS/JS Minifier
Minify CSS and JavaScript 🖼️ Image to Base64
Convert images to Base64 data URIs 📝 Markdown to HTML
Convert Markdown to HTML 📖 Swagger Generator
Generate OpenAPI specs
🎨 Design & Color
📊 Monitoring & Infrastructure
📋 Misc
🔗 UTM Link Builder
Build UTM links + shortener + click tracker 📋 Bulk WHOIS
Lookup 50 domains at once, CSV export ✅ Email Health Checklist
Free PDF lead magnet 🗺️ Sitemap Generator
Generate XML sitemaps 🚫 Blacklist Monitor
Monitor IPs/domains for blacklisting 💳 Crypto Payment Gateway
Accept BTC/LTC payments 📚 API Documentation
REST API for all tools
Build UTM links + shortener + click tracker 📋 Bulk WHOIS
Lookup 50 domains at once, CSV export ✅ Email Health Checklist
Free PDF lead magnet 🗺️ Sitemap Generator
Generate XML sitemaps 🚫 Blacklist Monitor
Monitor IPs/domains for blacklisting 💳 Crypto Payment Gateway
Accept BTC/LTC payments 📚 API Documentation
REST API for all tools
💡 Want your tool listed?
This is an open-source curated list. Email us to suggest a free developer tool.
All tools listed are free, open-source, and privacy-respecting. No ads, no tracking, no signup required.
🔧 For domain owners
📊 Professional Email Health Report
Get a detailed PDF audit with step-by-step fixes for your domain's email setup. Includes MX, SPF, DKIM, DMARC scores and recommendations.
Get Fix Report — €9 →