The Ultimate List of 51 Free Developer Tools — No Ads, No Signup, No BS

There are thousands of "free developer tools" lists out there. Most are SEO spam — pages that list 200 tools but haven't actually tested any of them. Half the links are dead. The other half require signup.

We took a different approach: we built the tools ourselves. All 51 of them run on korpo.pro. No third-party dependencies that could break. No signup walls. No email capture before you see results. Just tools that work.

Here's the complete list, by category:

📧 Email & DNS (9 tools)

Everything you need to diagnose email deliverability. Check your MX records, SPF, DKIM, DMARC, blacklist status, and more.

• Email Checker — Full deliverability audit with scoring
• Email Health Report — Professional PDF report for €9
• Spam Score Checker — 15+ spam signals analyzed
• Email Header Analyzer — Parse and explain all headers
• DMARC Record Generator — Generate DMARC DNS records
• DMARC Report Parser — Parse XML aggregate reports
• DNS Lookup — A, AAAA, MX, NS, TXT, CNAME, SOA
• DNS Propagation Checker — Check DNS globally
• Reverse DNS Lookup — PTR + forward-confirm

🌐 Web & SEO (10 tools)

Audit any website. Check SEO meta tags, SSL certificates, HTTP headers, redirect chains, and backlinks.

• SEO Meta Tag Analyzer — Title, description, OG tags
• WHOIS Domain Lookup — Registrar, expiry, nameservers
• SSL Certificate Checker — Expiry, issuer, chain
• HTTP Headers Checker — Security headers, CORS
• HTTP Status Checker — Bulk URL status codes
• Redirect Chain Checker — Follow 301/302 hops
• Meta Tag Preview — Preview OG + Twitter cards
• Backlink Checker — Who links to a URL
• IP Address Lookup — GeoIP, ISP, hostname
• IP Reputation Checker — Blacklist + abuse score

🛠️ Developer Utilities (10 tools)

Everyday tools that save you from opening ten tabs. JSON, Base64, URL encode, hashing, and more.

• JSON Formatter — Format, validate, minify
• Base64 Encoder/Decoder — Encode and decode
• URL Encoder/Decoder — URL encode/decode text
• Hash Generator — MD5, SHA-1, SHA-256, SHA-512
• Subnet Calculator — CIDR, netmask, IP range
• SSL Certificate Generator — Self-signed certs
• CSS/JS Minifier — Minify CSS and JS
• Image to Base64 — Convert to data URIs
• Markdown to HTML — Convert MD to HTML
• Swagger Generator — OpenAPI specs

🎨 Design & Color (2 tools)

• Color Picker — HEX, RGB, HSL conversion
• Contrast Checker — WCAG AA/AAA ratios

📊 Monitoring & Infrastructure (5 tools)

• Dead Man's Switch — Cron job monitoring
• Website Change Monitor — Detect page changes
• DNS Record Monitor — Track DNS changes
• SSL Expiry Reminders — Never miss renewal
• Status Page Hosting — Public status pages

📋 Misc (5 tools)

• UTM Link Builder — Links + shortener + tracker
• Bulk WHOIS — 50 domains at once, CSV export
• Email Health Checklist — Free PDF lead magnet
• Sitemap Generator — XML sitemaps
• Blacklist Monitor — IP/domain monitoring

📋 View All 51 Tools →