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CaptainDNS

Email Diagnostics

Tools to verify and validate your email authentication setup.

SPF
DKIM
DMARC
DMARCbis
BIMI
MTA-STS
TLS-RPT
DANE / TLSA

Deliverability

Email deliverability auditMail header analyzerEmail testerIP Blacklist CheckerDomain Blacklist CheckerSPF FlattenerDKIM Selector FinderSMTP/MX Tester

Secure & Monitor

Record generators, policy hosting and continuous monitoring.

Network & Web

Network tools, web page analysis and certificates.

IP Tools

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.

Certificates & BIMI

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.

Web

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.

Redirect Checker

Analyze HTTP redirect chains

Domain Redirect

Redirect your domains with automatic HTTPS and 301/302 redirects.

HTTP Uptime Monitor

Monitor your sites with scheduled HTTP checks and email alerts.

Status Pages

Publish a public status page grouping your HTTP monitors.

Developer Tools

Text utilities and tools for everyday dev work.

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.

Webhooks: coming soon

Webhooks let CaptainDNS push events to your systems in real time, without having to poll the API. They are under development for V2 of the public API and are not yet available in production. This page explains the plan and the alternatives to use in the meantime.

Status

  • V1 (current): webhooks not available.
  • V2 (planned): event emission, HMAC signature, retry with exponential backoff, and a delivery monitoring dashboard.

No firm date has been announced for V2. Progress will be communicated in the changelog and on the CaptainDNS blog.

Planned use cases

Here are the events under consideration for V2:

  • api_key.rotated: a key has been rotated, the old one enters the grace period. Useful to update your secrets manager automatically.
  • api_key.revoked: a key has been revoked. Useful to immediately pull a compromised integration.
  • api_key.expires_soon: a key is approaching its expiration date (typically T-30 days).
  • usage.threshold_reached: credit consumption crosses a threshold (80 %, 100 %, 120 %).
  • usage.overage_reported: the monthly overage has been successfully billed via Paddle.
  • monitoring.alert: an anomaly is detected on a key (spike ten times the average, 429 storm, etc.).

These events are proposals; the final list will be locked after feedback from V1 users.

Temporary alternatives

Until V2 ships, use one of the following patterns:

Polling via response headers

Every public API response includes X-Credits-Remaining and X-Credits-Limit headers. A daily cron calling a low-cost endpoint is enough to trigger alerts on consumption thresholds.

You can also check your usage in the CaptainDNS dashboard (Account > API usage).

Client-side monitoring

In your client, watch the X-Credits-Remaining and X-RateLimit-Remaining response headers. If either drops under a critical threshold, trigger a homemade alert.

Scheduled canary

Run a scheduled job that calls a cheap endpoint (for example POST /public/v1/resolve on a canary domain) and logs the status and headers. A sequence of unexpected 401/403 points to a problem, and the X-Credits-Remaining metric serves as an early signal for plan upgrades.

What V2 will bring

When webhooks ship, you will be able to:

  • Register an HTTPS endpoint in the /account/webhooks dashboard.
  • Pick events via a set of checkboxes.
  • Define a shared secret to verify the HMAC signature of each delivery.
  • Consult the delivery dashboard with successes, failures and retry queue.
  • Manually replay a failed delivery from the dashboard.

The Starter plan should include 3 endpoints, Pro 10, Business and Enterprise unlimited (subject to a fair-use policy).

Stay informed

To be notified when webhooks launch:

  • Subscribe to the CaptainDNS blog: major feature launches are announced in dedicated posts.
  • Watch the public API changelog, updated on every release.
  • Enterprise customers with an account manager will receive a pre-announcement by email, with the option to test the beta.

In the meantime, the quickstart and the OpenAPI reference remain the best entry points to integrate today.