AI-first diagnostics
AI Engineer for Your Website
The Enterno.io AI engineer checks your site — HTTP headers, SSL, DNS, speed — finds problems and writes a clear fix spec. 10 free monitors, no card required.
AI finds the problem — and writes the fix spec
Example report: the scan on the left, a ready-to-hand developer spec on the right.
Scanning example.com
67%
- HTTPS✓
- Content-Security-Policy✗
- Caching!
- DNS & MX✓
- Speed (LCP, TTFB)
32 of 48 checks done…
Problem found
Missing Content Security Policy (CSP)
The site does not send a Content-Security-Policy header. This raises the risk of XSS attacks and injections.
Ready spec for the developer
add_header Content-Security-Policy "
default-src 'self';
script-src 'self';
style-src 'self';
object-src 'none';
base-uri 'self';
frame-ancestors 'none';
" always;The spec is generated by AI from the detected problem and security best practices. Illustrative example.
How It Works
Three simple steps to a full analysis
01
Check
48+ tools scan your site in seconds
02
AI diagnosis
AI finds problems and explains the causes
03
Ready spec
Copy the instructions and hand them to a developer
All Tools
Comprehensive analysis and monitoring for your website
Website Analysis
12Domain & DNS
10Network
8Security & Email
11Why enterno.io
319.2K+
Checks Performed
218+
Active Monitors
5.0K+
API Requests
67+
Free Tools
01
Free
All basic tools available without registration or limits
02
Fast
Results in seconds. Servers in Russia — minimal latency
03
API Access
REST API to automate checks and integrate into your projects
04
24/7 Monitoring
Telegram and email alerts for site outages or SSL expiration
05
Telegram alerts
Instant notifications on outages, SSL expiry and DNS problems
06
Status pages
Public status pages for your services and clients
Articles & Guides
Useful resources on web development and administration
Latest articles
SSL/TLS
Russian Trusted Root CA: why browsers reject it and how to install
Russian bank sites fail in Chrome, Safari and Firefox: the Ministry root is in no trust store. How to install it per pla
Networking
How to Test a Mail Server: SMTP, TLS, Relay and PTR
How to test a mail server: the SMTP greeting, STARTTLS support, open relay, the PTR record and blocklists. Five checks w
DNS
Cloudflare DNS 1.1.1.1: Addresses, Setup and Why It Fails
Cloudflare DNS addresses 1.1.1.1, 1.1.1.2 and 1.1.1.3, router and system setup, DoH and DoT. Why 1.1.1.1 stays silent fo
DNS
AdGuard DNS: Addresses, Setup and What It Actually Blocks
AdGuard DNS addresses for all three modes, setup on a router, Windows, macOS and Android, plus DoH, DoT and DoQ. What a
Popular guides & reference
Glossary
all →
Core Web Vitals — LCP, INP, CLS in 2026
Core Web Vitals are Google's three key UX and ranking metrics: LCP, INP (replaced FID), CLS. Thresholds, how to improve.
robots.txt — What It Is and How It Works
robots.txt is a file with instructions for search bots. User-agent, Disallow, Allow, Sitemap, Crawl-delay. Common mista…
How-to
all →
How to check if a website is blocked in Russia
Diagnose a site blocked in Russia: check the Roskomnadzor EAIS registry, availability from Russian nodes (Moscow, St. P…
How to check a domain in the Roskomnadzor registry (EAIS)
Check a domain in Russia’s unified register of prohibited information (EAIS): official lookup at eais.rkn.gov.ru, groun…
Ports
all →
Port 9100 (TCP) — Prometheus node_exporter
Port 9100 is used by Prometheus node_exporter. Standard port for node_exporter. Security, how to check, best practices.
Port 10250 (TCP) — Kubernetes kubelet API
Port 10250 is used by Kubernetes kubelet API. Standard port for kubelet. Security, how to check, best practices.
Alternatives
all →
SSL Labs Alternatives — Best SSL Checkers 2026
SSL Labs Qualys is unreliable in 2026. 7 alternatives for SSL certificate testing: Enterno.io, Hardenize, ImmuniWeb, Cr…
MXToolbox Alternatives 2026 — DNS & Email Tools
MXToolbox cut its free tier in 2024. 6 alternatives for DNS/MX/blacklist checks: Enterno.io DNS, Google Dig, intoDNS, D…
SSL errors
all →
ERR_BLOCKED_BY_RESPONSE: X-Frame-Options, CSP and CORP — Fix
an iframe refused by X-Frame-Options or CSP frame-ancestors is the usual cause; CORP and COEP are rarer. How to tell wh…
ERR_HPACK_DECODING_FAILED — HTTP/2 Header · Browser Error Fix
Chrome ERR_HPACK_DECODING_FAILED — HTTP/2 HPACK decompression error. Malformed headers, encoder state corruption.
Research
all →
LLM shares 2026: four metrics, four winners
By human visits OpenAI leads (~53%), by crawler traffic Google (24.8%), among developers Anthropic (39%). None of the a…
Headless CMS 2026: the share is structurally unmeasurable
Our measurement of 401 pages found headless systems on 11 — 2.7% against a third for traditional ones. But that is not …
Simple, transparent pricing
Start free. Upgrade when you need more control.
What our users say
Switched from UptimeRobot to Enterno — faster monitoring, better UI, and everything in Russian. Now tracking 30+ client sites.
Simple, clear API. Integrated checks into CI/CD in an hour — now every deploy automatically verifies SSL and security headers.
Perfect tool for freelancers. Free plan covers my needs, and I send PDF reports to clients as-is.
SSL Encrypted
Hosted in Russia
GDPR / 152-FZ Compliant
99.9% Uptime SLA
HTTP Headers Analysis Tool
Check HTTP response headers, status codes, redirect chains, server timing, and security headers for any website. Our tool sends a real request from a server in Russia and shows the complete response including all headers, cookies, and performance metrics. Use it to debug caching, security configuration, CORS, and content delivery.
Frequently Asked Questions
What are HTTP headers?
HTTP headers are metadata sent between a browser and a server with every request and response. They control caching, security, content type, redirects, and many other aspects of how a web page is delivered.
How to check HTTP headers of a website?
Enter any URL in the form above and click Check. The tool will show all response headers, status codes, redirects, cookies, and a security header analysis.
What security headers should every site have?
Key security headers include Content-Security-Policy, Strict-Transport-Security (HSTS), X-Content-Type-Options, X-Frame-Options, and Permissions-Policy. They protect against XSS, clickjacking, and other common attacks.
What does the status code mean in HTTP response?
HTTP status codes indicate the result of a request: 2xx means success, 3xx means redirection, 4xx means client error (e.g., 404 Not Found), and 5xx means server error. The exact code helps diagnose issues.
Is this tool free?
Yes, the HTTP header checker is completely free with no limits on the number of checks. You can also create a free account to save your check history and access additional features.
What is HSTS and why is it important?
HSTS (HTTP Strict Transport Security) is a header that tells the browser to always use HTTPS for a given site. It prevents protocol downgrade attacks and traffic interception through insecure HTTP connections.
How to check redirect chains?
Our tool automatically follows all redirects (301, 302, 307, 308) and shows the complete redirect chain. Long chains slow down page loading and weaken SEO — it is recommended to have no more than 1-2 redirects.
How to set up 24/7 website uptime monitoring?
Sign up free, add a URL on <a href="/en/monitors">/en/monitors</a>, pick an interval (1-5 min) and alert channels (Email, Telegram, Slack, webhook). The free Scout plan includes 10 monitors forever, no card. Checks run from Russia (MSK), Europe (DE), and US (East) on the Pro plan.
What are Core Web Vitals and how to improve them?
Core Web Vitals — 3 Google speed metrics: LCP (main content paint, < 2.5 s — good), CLS (layout shift, < 0.1), INP (click responsiveness, < 200 ms). They affect ranking. Test your site via <a href="/en/speed">/en/speed</a> — the tool returns a 0-100 score and concrete opportunities: lazy-loading, image compression, CSS/JS minification.
Are there Telegram, Slack and PagerDuty integrations?
Yes. All major channels integrate in one click: Email, Telegram (via our @enterno_io_bot), Slack (webhook), Discord (webhook), PagerDuty (Events API v2), Jira (auto-create issues), webhooks with HMAC signing. Plus SMS and Opsgenie on the Business plan. Configure in Settings → Notifications.
200+ HeadersFull set of HTTP response headers
Security HeadersCSP, HSTS, X-Frame-Options and more
Redirects301/302 redirect chains
Custom UASimulate browsers and crawlers
Why teams trust us
150+
headers analysed
HSTS
security check
<2s
response time
Free
no signup needed
How it works
1
Enter URL
2
Get all headers
3
Check security
What are HTTP Headers?
HTTP headers are metadata exchanged between browser and server on every request. They control caching, security, compression, and redirect behavior.
Full Analysis
All response headers categorized: security, cache, content.
Fast Results
Results in seconds from any device without registration.
Redirect Tracing
Visualize redirect chains — each hop with status code and URL.
Check History
Save and compare results — track header changes over time.
Who uses this
DevOps
server header check
Security
CSP, HSTS, X-Frame audit
Developers
cache header debugging
SEO
redirect chain check
Common Mistakes
Missing HSTSWithout HSTS the browser may make the first request over HTTP. Add
Strict-Transport-Security.No Content-Security-PolicyCSP prevents XSS attacks. Even a basic CSP is better than none.
Missing X-Frame-OptionsWithout it, your site can be embedded in an attacker's frame (clickjacking).
Server exposes version
Server: Apache/2.4.51 helps attackers find vulnerabilities. Hide the version.Best Practices
Enable HSTS with preloadThe
preload directive adds the domain to the browser's built-in HSTS list.Configure Cache-ControlUse
immutable for static assets and no-store for sensitive pages.Check after each deployServer updates can reset security headers. Check after every deploy.
Use monitoringSet up an HTTP monitor to get notified when status or headers change.
Get more with a free account
HTTP header check history, API keys and uptime monitoring.
Sign up free