Log in
CaptainDNS

Propagation & diagnostics

Compare resolvers worldwide and inspect returned answers.

Email authentication

Tools to verify and validate your email authentication setup.

SPF syntax validator

Review include chains and DNS query limits before publishing changes.

SPF record inspector

Resolve the published TXT record, flag lookup limits and decode each mechanism.

DKIM syntax validator

Quickly check the syntax of your DKIM records.

DKIM record check

Resolve a selector and analyse the published DKIM TXT record.

DMARC syntax validator

Check rua/ruf destinations, alignment modes and the active policy before publishing.

DMARC record inspector

Resolve the published policy, surface diagnostics and confirm enforcement before switching to reject.

BIMI syntax validator

Validate BIMI tags, the logo fetch and the VMC certificate before publishing.

BIMI record inspector

Resolve the published BIMI record, inspect logo and VMC diagnostics in one place.

Email deliverability audit

Audit MX, SPF, DKIM and DMARC to confirm a domain is ready to send.

Mail header analyzer

Decode participants, authentication results and routing from raw headers.

DMARC record generator

Create compliant DMARC records with all policy and reporting options.

Text

Transform, encode and measure your content in seconds.

Text case converter

Convert any block of text to upper or lower case instantly.

Base64 encoder / decoder

Encode or decode any content in Base64 without leaving the browser.

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.

Images

Preview and validate your BIMI logos before publishing.

BIMI logo lookup

Inspect a BIMI logo URL—format, metadata and live rendering—before rollout.

Certificates

Inspect CSRs, BIMI logos and VMC certificates before you deploy.

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.

IP

Look up addresses, owners, reverse records and ranges.

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.

My IP address

Detect your IPv4/IPv6 addresses and their geolocation.

Text tools

Practical utilities for copy, payloads, and content hygiene

Discover lightweight helpers dedicated to text transformations. Whether you need to refactor copy, clean payloads, or check a snippet before publication, each tool keeps the workflow in the browser.

Text case converter

Switch entire paragraphs between lower and upper case instantly, without leaving the browser.

Base64 encoder / decoder

Encode or decode Base64 strings for API payloads, webhook bodies or DNS TXT records in seconds.

Slug generator

Turn any heading into a clean slug ready for CMS fields, URLs or anchors.

Word & character counter

Gauge copy length with real-time word and character totals, handy for emails, tickets or DNS record descriptions.

Why start with text helpers

Everyday tasks, automated

Copywriting, incident reports, change logs – many short tasks require rewriting the same text in a different casing or checking its length. Instead of relying on a local editor or ad hoc scripts, the tools apply the transformation in the browser. Nothing is stored server side once the API returns the result.

Need to unwrap a webhook body or prepare an Authorization header? The Base64 encoder/decoder runs the conversion through the API and returns only the processed payload, perfect for secrets, TXT records or integration tests.

Works with large snippets

The converter accepts multi-paragraph content. Textarea resizing and keyboard shortcuts (⌘+⏎ / Ctrl+⏎) let you trigger the conversion without touching the mouse. If the payload is too large, the interface immediately highlights it with a clear error message.

Count before publishing

Need to respect a subject line limit or confirm the size of a TXT record? The counter surfaces word and character totals instantly. It helps estimate reading time, stay within API quotas, or double-check message templates before they leave Drafts.

What comes next

More utilities will join this section: smart trimming helpers, transliteration shortcuts, and DNS-focused generators that do not fit in the existing suites. Each addition follows the same principles – instant feedback, accessible UI, and privacy by default.