Sysadmin Tools

Free, fast, no-login utilities for IT professionals. No tracking, no accounts, no nonsense. Just the tools you actually use at 2am when something is on fire.

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How exposed is your site?

Get a free security grade (A–F) for any domain in seconds. We check TLS, DNS, email authentication, and exposed ports — then hand you a shareable badge.

Audit your site now

Sysadmin Tools earned a security grade of A, 94 out of 100

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DNS Lookup

Query authoritative DNS servers for any domain. Supports A, AAAA, MX, TXT, NS, CNAME, SOA, PTR.

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Subnet Calculator

Calculate network, broadcast, host range, and wildcard mask for any IPv4 or IPv6 CIDR.

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What Is My IP

See your public IPv4 and IPv6 address, reverse DNS, ISP, and approximate location.

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DMARC / SPF / DKIM

Look up any domain's email authentication records. Check DMARC policy, SPF, and DKIM at common selectors.

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HTTP Headers Checker

Inspect response headers, redirect chains, and security headers (HSTS, CSP, X-Frame-Options) for any URL.

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SSL/TLS Checker

Look up any server's SSL/TLS certificate: subject, issuer, validity, SANs, full chain, and SHA-256 fingerprint.

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Open Ports

Look up what service usually listens on a given port, then quick-scan your own box for open ports. Local probe runs against your IP only — no third-party targets.

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WHOIS Lookup

Look up the registration record for any domain — registrar, creation and expiry dates, status codes, and authoritative nameservers.

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DNS Propagation

Check whether a DNS record has propagated globally. Queries your domain against 8 public resolvers at once.

About this site. Built by IT folks, for IT folks. DNS lookups run server-side via dig. Subnet math runs in your browser. Your IP is detected from the request headers — we don't log it. Questions or feedback? Open an issue on GitHub.