Free DNS & Sysadmin Tools

Standalone utilities that don't need a full domain scan: build and validate records, generate keys, check propagation, and more. Everything below runs client-side or through this same no-account, no-tracking backend.

Last updated: September 10, 2026

DNS & Email

Build and validate the DNS records that make your outbound mail authenticate cleanly, plus general DNS lookups and propagation checks.

SPF Record Builder

Build a valid SPF record mechanism-by-mechanism, with a live RFC 7208 lookup-count meter so you catch a permerror before it ships.

📖 Guide

DKIM Key Pair Generator

Generates an RSA-2048 (or Ed25519, where your browser supports it) key pair locally. The private key never leaves your browser, formatted for a selector._domainkey TXT record.

📖 Guide

DMARC Record Checker & Builder

Checks what policy a domain currently publishes, and builds a new v=DMARC1 record field-by-field with the safe none → quarantine → reject rollout built in.

📖 Guide

BIMI Record Generator

Builds the default._bimi TXT record for your logo, and flags when DMARC isn't enforced strictly enough for it to actually apply.

📖 Guide

MTA-STS & TLS-RPT Generator

Generates the _mta-sts and _smtp._tls TXT records plus the mta-sts.txt policy file your enforcement mode needs.

📖 Guide

Parked Domain & Wildcard Anti-Spoofing Generator

Generates the SPF, Null MX, DMARC and wildcard DKIM records that stop a parked domain — or unused subdomains under an active one — from being spoofed.

📖 Guide

Global DNS Propagation Checker

Queries a record across a dozen independent public resolvers spread across the US and Europe to confirm a change has actually propagated.

📖 Guide

Network & Infrastructure Utilities

General-purpose networking calculators and connectivity checks.

IPv4 / IPv6 Subnet & CIDR Calculator

Network/broadcast address, netmask, wildcard mask, and usable host count from CIDR notation, for both IPv4 and IPv6.

📖 Guide

SSL/TLS Certificate Deep Inspector

Full chain validation, negotiated protocol/cipher, key strength, SAN coverage, and a downloadable expiry reminder.

📖 Guide

Port & Mail Server Connectivity Tester

Open/closed checks on 25, 465, 587, 143, 993, 110, 995, 21, 22, 80, 443 (plus a custom port) with banner and STARTTLS detection.

📖 Guide

Web & Server Security Diagnostics

Checks aimed at the web-facing side of your infrastructure, not just mail.

HTTP Security Headers Analyzer

Grades HSTS, CSP, X-Frame-Options, Referrer-Policy, Permissions-Policy and X-Content-Type-Options on any URL with an A-F score.

📖 Guide

Deep Scan: Attack Surface & Exposure Audit

A heavier audit: TLS protocol depth, cookie/CSP hygiene, known-vulnerable JS libraries, and a sweep for accidentally exposed .git/.env/backup files and leaked API keys or PII.

Subdomain Takeover Checker

Scans common subdomain names for a dangling CNAME to a third-party platform (GitHub Pages, S3, Heroku, Netlify, Vercel and more) that could be silently hijacked.

📖 Guide

CAA Record Checker & Builder

Checks which certificate authorities a domain has authorized to issue for it, with an RFC 8659 parent-domain walk, and builds a new record if you don't have one yet.

📖 Guide

Typosquatting & Lookalike Domain Checker

Generates common typo and homoglyph variants of a domain, omissions, transpositions, hyphenation, TLD swaps, and checks which ones are actually registered.

📖 Guide

SEO & Search Visibility

Checks aimed at whether search engines can actually find and index what you've published.

Site Indexing Audit

Crawls any site and scores it on SEO, GEO (AI answer-engine readiness), AEO (featured snippets), and Google's own indexing criteria — HTTP status, noindex signals, canonical tags, and content depth.

Identity & System Administration

General sysadmin utilities that don't fit neatly under DNS, but come up constantly alongside it.

JWT Debugger & Decoder

Decodes a JWT's header, payload and timestamps entirely in your browser. Nothing is sent anywhere.

📖 Guide

Htpasswd & Password Entropy Generator

High-entropy password generation with a bit-entropy readout, plus bcrypt, APR1-MD5, and SSHA htpasswd hashing.

📖 Guide

Cron Expression Builder & Explainer

Converts crontab syntax to plain English and back, for scheduling backup/maintenance jobs.

📖 Guide

Guides

Plain-language reference for every DNS record type this site checks, how to set each one up, and how to troubleshoot it.

DNS & Email Record Guides

A full reference covering every record type on this site, plus a step-by-step roadmap tying it all together. Eighteen guides in all.