
AdGuard DNS (94.140.14.14): filtering, privacy, and Family mode
AdGuard DNS is a public DNS resolver that can block ads/trackers (and, in Family mode, adult content). Addresses, DoH/DoT/DoQ, and an action plan.
New tools
100% freeMTA-STS & BIMI hosting, DMARC & TLS-RPT monitoring
CaptainDNS hosts your MTA-STS policy and BIMI logo, and monitors your DMARC and TLS-RPT reports automatically. All free, no server required.
Google, Yahoo and Microsoft now require stronger email authentication. Protect your deliverability in just a few clicks.

AdGuard DNS is a public DNS resolver that can block ads/trackers (and, in Family mode, adult content). Addresses, DoH/DoT/DoQ, and an action plan.

1.1.1.1 is Cloudflare's public DNS resolver. Here's how to use it properly (addresses, DoH/DoT/ODoH, tests, pitfalls) and deploy it.

Quad9 (9.9.9.9) is a public DNS resolver focused on security and privacy: malware blocking, DNSSEC validation, and encrypted DoT/DoH options. Here's how to deploy it properly.

Add the CaptainDNS MCP server to ChatGPT and use 3 widgets to troubleshoot DMARC/DNS and analyze email headers without leaving the conversation.

Putting your logo in the inbox: what you actually need to configure in DNS for BIMI, and how to choose between VMC and CMC.

Gmail and Yahoo require a one-click unsubscribe via RFC 8058-compliant List-Unsubscribe headers. Here's the expected format, the server-side POST, and the compliance checklist.

IPv4 vs IPv6: address sizes, performance, security, NAT, DNS... Learn how to differentiate ipv4 and ipv6, what ipv6 vs ipv4 really means, the ipv4 and ipv6 difference for DNS, and how to keep both stacks coexisting.

Learn what Google Public DNS 8.8.8.8 is, how it works, its speed and reliability benefits, privacy drawbacks, how to configure it on Windows 11 or a router, and which alternatives (Cloudflare 1.1.1.1, OpenDNS, etc.) to consider.

Starting January 2026, Gmail will no longer continuously fetch messages from external mailboxes via POP ("Check mail from other accounts"). Impacts, timeline, and alternatives for Gmail and Google Workspace users and admins.
DNS Lookup
Choose a DNS record type to search for.
Propagation & diagnostics
Compare resolvers worldwide and inspect returned answers.
Keep history, monitor your zones and automate recurring checks.
Email authentication
Tools to verify and validate your email authentication setup.
Deliverability
IP tools
Quickly inspect an IP address or your own connection.
My IP address
Detect your IPv4/IPv6 addresses and their geolocation.
Reverse lookup
Resolve a PTR record and validate DNS consistency.
IP WhoIs
Identify the owner of an IP range and its contacts.
IPv4 netmask
Calculate network, broadcast and usable hosts for any IPv4 block.
IPv6 subnet calculator
Calculate IPv6 subnets, address ranges and reverse DNS entries.
Text
Transform and measure your content in seconds.
Text case converter
Convert any block of text to upper or lower case instantly.
Slug generator
Transform any sentence into an SEO-friendly slug in seconds.
Word & character counter
Measure the length of any text, with instant word and character counts.
Password generator
Generate strong random passwords and memorable passphrases instantly.
Developer
Encoding, hashing, regex and formatting for everyday dev work.
Base64 encoder / decoder
Encode or decode any content in Base64 without leaving the browser.
Hash Generator
Compute MD5, SHA-1, SHA-256 and SHA-512 hashes of any text.
URL encoder / decoder
Encode or decode text using percent-encoding (RFC 3986) right in your browser.
Regex Tester
Test a regular expression against text and visualize matches.
JSON / YAML Formatter
Format, validate and convert JSON and YAML in one click.
Web & Certificates
BIMI logos, VMC/CSR certificates and web page diagnostics.
BIMI logo lookup
Inspect a BIMI logo URL - format, metadata and live rendering - before rollout.
BIMI SVG converter
Convert any SVG to BIMI-compliant Tiny-PS format in seconds.
CSR parser
Inspect a CSR, extract subject details, fingerprints and requested SANs.
VMC inspector
Inspect a Verified Mark Certificate - issuer, validity and SAN coverage - before you publish BIMI.
Page size checker
Check if your page exceeds Google's 2 MB crawl limit.
Phishing URL Checker
Check if a URL is flagged as phishing or malware by 4 threat intelligence sources.