🛠️ 51 Free Developer Tools That Save You Hours Every Week
No ads. No signup. No credit card. Just tools that work.
Last updated: May 2026 · Jump to full list ↓
Every developer has a collection of bookmarks for quick tasks — checking DNS records, formatting JSON, looking up WHOIS data, generating hashes. You bounce between 8 different sites, close 3 popup ads, and waste 15 minutes on what should take 30 seconds.
Korpo.Pro puts 51 free developer tools in one place. No ads. No signup walls. No tracking. And if you need advanced features — Pro API access, PDF health reports, monitoring alerts — we offer those too, paid with crypto (BTC/LTC).
Here's the full toolkit:
📧 Email & Deliverability Tools
Score your domain's email setup (MX/SPF/DKIM/DMARC/blacklists) in seconds. 100-point scale with specific fix recommendations.
Analyze 15+ spam signals — trigger words, headers, authentication, blacklists. See exactly why emails land in spam.
Paste raw email headers, get a full breakdown: Received chain (every hop), SPF/DKIM/ARC results, 25+ fields explained.
Create professional HTML email signatures with photo, social icons, and custom colors. Works with Gmail, Outlook, Apple Mail.
Get a professional PDF audit of any domain's email setup. €9 one-time, crypto payments. Includes score card, DNS breakdown, and remediation steps.
🌐 DNS & Domain Tools
Query A, AAAA, MX, TXT, NS, CNAME, SOA records. Supports ANY type lookup.
PTR lookup + forward-confirm verification. Spot mismatched rDNS.
Check DNS records across 15 global resolvers. See propagation status worldwide.
Get registrar, creation/expiry dates, nameservers, and registrant info.
Paste up to 50 domains, get a table with expiry dates, registrars, and CSV export.
IP geolocation, ISP, ASN info. Check your VPS or any IP.
Check if an IP is on abuse lists, spam databases.
CIDR → network, broadcast, netmask, usable hosts, IP class.
🔒 SSL & Security Tools
Inspect cert issuer, expiry, SANs, TLS version, and chain validity.
Generate self-signed certs (RSA 2048/4096) with custom CN, org, validity.
Monitor cert expiry, get email alerts at 30/14/7 days. €5/mo.
Cryptographic-strength passwords. Entropy display, length 8-64, character sets. Uses secrets module.
MD5, SHA-1, SHA-256, SHA-384, SHA-512. Instant hashing with copy-to-clipboard.
📈 SEO & Web Tools
Meta tags, headings, links, images, schema — full on-page SEO audit.
Generate OG, Twitter Card, and standard meta tags with previews.
See how any URL renders in Google, Facebook, and Twitter cards.
7 schema types: Organization, Article, Product, FAQ, Breadcrumbs, HowTo, LocalBusiness.
Discover backlinks, domain authority estimation, anchor text analysis. €9/mo.
Crawl any site up to 200 pages and generate standards-compliant XML sitemaps.
Build UTM-tagged URLs with short link generation and click tracking.
Follow 301/302/303/307/308 redirects, detect loops, show full chain.
Bulk URL status code checker. See which endpoints are up/down/redirecting.
Security headers, CORS, caching — full response header analysis.
⚙️ Developer Tools
Format, validate, and beautify JSON. Download output button.
Bidirectional conversion: JSON→CSV and CSV→JSON.
Encode/decode text to/from Base64. Copy+download output.
Upload any image, get base64 data URI for embedding in HTML/CSS.
Percent-encode or decode URLs and query strings.
Convert Markdown to HTML with live preview. Supports fenced code, tables.
Minify and beautify CSS or JavaScript. See byte savings.
Generate QR codes from text/URL. Download as PNG. Configurable size + error correction.
HEX, RGB, HSL, CMYK instant conversion. Harmony palette generator.
WCAG AA/AAA compliance. Check text/background contrast ratios with live preview.
Download a complete FastAPI+Jinja2 starter kit with auth and crypto payments.
Build OpenAPI 3.0.3 specs interactively. YAML/JSON export. €7/mo.
Capture full-page screenshots of any URL. 4 viewport sizes. Free 100/month.
📊 Monitoring & Alerts
Monitor URLs every 5 minutes. Email alerts when down. Free 5 URLs.
SHA-256 checksum detection. Alert when any page changes. €7/mo.
Track DNS record changes. Alert on MX/SPF/DKIM modifications. €7/mo.
WHOIS expiry tracking with progressive alerts at 90/60/30 days. €7/mo.
If you don't check in, your alerts fire. Cron job monitoring. €5/mo.
Check 8 DNSBLs. Monitor IPs and domains for blacklisting. €9/mo.
🎯 Other Free Tools
Create free bio pages with custom links, avatar, and accent colors.
Customizable GDPR cookie banners. Copy/paste HTML+CSS+JS.
Self-host a professional status page for your services.
Accept BTC/LTC payments. xpub-based (no private keys). Self-hosted.
⚡ Start Using All 51 Tools Now
No ads. No signup. No credit card. Just tools that work.
Want the full audit? Get the €9 PDF report ·
Power user? Pro API — €9/mo
Crypto-native: BTC/LTC accepted · No bank, no KYC
📊 Professional Email Health Report
Liked this article? Put it into practice — get a personalized email deliverability audit for your domain.
Get Fix Report — €9 →