What Is PortJar?
PortJar is a free, browser-based network engineering toolkit that solves a problem every developer and sysadmin knows: you have 8 single-purpose sites bookmarked, half of them paywalled, the other half buried under ads, and you're context-switching between them for tasks that take 30 seconds each.
PortJar puts 29 of those tools in one place — DNS lookup, WHOIS, port checking, TLS/SSL inspection, SPF/DMARC validation, CIDR/subnet calculator, hash generators, Base64 encoders, regex testers, and more. No signup, no install, no ads blocking your workflow.
The Tool Set
The 29 tools span five categories:
- DNS & IP: DNS lookup, reverse DNS, IP geolocation, BGP/ASN lookup, WHOIS
- Connectivity: Port checker, ping, traceroute, HTTP headers inspector
- TLS/Security: SSL/TLS certificate inspector, cipher checker
- Email: SPF record lookup, DMARC checker, MX record inspector, blacklist check
- Utilities: CIDR/subnet calculator, Base64 encoder/decoder, hash generator (MD5/SHA), regex tester, URL encoder
Client-side tools — CIDR, hash, regex, encoders — run entirely in your browser, nothing sent to a server. Server-side tools — DNS, WHOIS, port, TLS, SPF — run with SSRF guards and tiered rate limiting: first 10 requests free, then paced. Clean JSON output on everything.
The UX Case
The value proposition isn't any individual tool — it's the consolidation. Network debugging rarely requires just one lookup. You check DNS, then TLS, then SPF, then port availability — four different sites if you're using the typical bookmark stack. PortJar keeps you in one tab, one interface, one search pattern. The context-switch cost is real and PortJar eliminates it.
Each tool page ships approximately 4KB of route JS on top of a 102KB shared runtime — lean for a Next.js app, and it shows in load times.
Technical Stack
Built on Next.js 15 + React 19 + Tailwind CSS, tested with Vitest. Everything is statically rendered except the API routes that call upstream services. This matters for performance — tool pages load fast because they're pre-rendered, not server-rendered on every request.
Pricing
| Tier |
Cost |
Limits |
| Free |
$0 |
First 10 server-side requests free, then rate-limited. Client-side tools unlimited. |
Entirely free. No paid tier, no freemium gate. Rate limiting on server-side tools is the only constraint — and client-side tools (CIDR, hash, regex, encoders) are completely unlimited.
Who It Is For
Network engineers and sysadmins who run frequent DNS, port, and TLS checks as part of daily workflow. Developers debugging email deliverability, SSL issues, or API connectivity. DevOps and platform engineers who need quick subnet calculations and IP routing lookups. Security practitioners doing lightweight recon — port scanning, TLS cipher checking, blacklist lookups.
Limitations
Rate limiting: Server-side tools allow 10 free requests before pacing kicks in. For heavy users this may be a friction point — though client-side tools are fully unlimited.
No API: PortJar is a UI toolkit, not an API service. Teams wanting to integrate these checks into pipelines or scripts will need to use dedicated API services like SecurityTrails, Shodan, or MXToolbox.
Early stage: 29 tools is a strong start but the public roadmap signals more to come — expect the tool set to evolve.
No account/history: No login means no saved results, no history, no team sharing. Every session starts fresh.
Verdict
PortJar is exactly what it says: a free network toolkit that eliminates the bookmarks folder. The consolidation of 29 tools into one clean, fast, no-signup interface is the product — and it delivers. The rate limiting on server-side tools is a real constraint for power users, and the lack of an API limits pipeline use cases. But for the daily workflow of DNS lookups, TLS checks, SPF validation, and subnet math, PortJar is the tab you leave open and stop thinking about.