Why analyze web pages with HTTP tools?

HTTP tools detect invisible issues: pages too heavy for Googlebot, misconfigured headers, redirect loops. These problems directly impact your rankings without you knowing.

What is Googlebot's 2 MB limit?

Google limits the HTML content it can index to approximately 2 MB (2,097,152 bytes). Beyond that, content is truncated: elements at the bottom of the page (links, FAQ, SEO text) are not considered for ranking.

Are these tools free?

Yes, all CaptainDNS HTTP tools are 100% free with no sign-up required. Analyze as many pages as you need.

CaptainDNS

DNS Lookup

Choose a DNS record type to search for.

Propagation & diagnostics

Compare resolvers worldwide and inspect returned answers.

Propagation testPublic resolvers, remaining TTLs, divergent responses.
Domain DNS auditParent/local NS, authority and response times.
API & integrations
Keep history, monitor your zones and automate recurring checks.

Email authentication

Tools to verify and validate your email authentication setup.

Syntax validation

Record inspectors

Generators

SPF

SPF syntax validator

SPF record inspector

SPF record generator

DKIM

DKIM syntax validator

DKIM record check

DKIM generator

DMARC

DMARC syntax validator

DMARC record inspector

DMARC record generator

BIMI

BIMI syntax validator

BIMI record inspector

BIMI record generator

MTA-STS

MTA-STS syntax validator

MTA-STS record inspector

MTA-STS generator

TLS-RPT

TLS-RPT syntax validator

TLS-RPT record inspector

TLS-RPT generator

Deliverability

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.

Email tester

Send a test email and get instant authentication and deliverability feedback.

IP Blacklist Checker

Check if your IP is on email blacklists

Domain Blacklist Checker

Check if your domain is on URI blacklists

SPF Flattener

Flatten SPF records to reduce DNS lookups below the 10-lookup limit.

DKIM Selector Finder

Auto-discover all DKIM selectors for a domain via DNS brute-force.

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.

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.

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.

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.

HTTP Tools

Analyze your web pages: size, headers and crawl limits

Tools to diagnose HTTP issues on your web pages: page size analysis, header inspection, Googlebot crawl limit check and truncation simulation.

Page Size Checker

Measure the actual size of your web pages and check whether they exceed Googlebot's 2 MB crawl limit.

Why use HTTP tools?

HTTP is the foundation of every web page. An HTTP issue means poorly indexed content, a slow site or wasted resources. Without HTTP analysis, you have no idea what Googlebot actually sees on your pages.

Three situations where these tools are essential:

Page too heavy → Googlebot truncates HTML beyond 2 MB, causing your internal links and FAQ to disappear from the index
Incorrect headers → A misconfigured Content-Type or a forgotten X-Robots-Tag: noindex can deindex an entire page
Crawl budget optimization → Reducing page size lets Googlebot crawl more pages within its allotted time

Complementary tools

Tool	Purpose
DNS Lookup	Check your domain's DNS resolution
Email Deliverability Audit	Analyze MX, SPF, DKIM and DMARC for your domain
DNS Propagation Checker	Confirm that your DNS changes have propagated