Free website monitoring with real-time alerts

Website monitoring: why you need to track URL availability

Website monitoring is the practice of continuously checking the availability, latency, and integrity of an HTTP URL. A monitoring tool sends a request at a regular interval, records the response, and triggers an alert on failure. This lets you catch an outage before your users do.

A 2024 Gartner study puts the average cost of one hour of downtime at $5,600 for a small business and up to $540,000 for a Fortune 1000 company. Without uptime monitoring, you discover the incident through an angry customer email, sometimes hours after the outage. In the meantime, your conversion funnel is broken, your forms no longer submit, and your SEO degrades.

CaptainDNS provides a free tool to monitor up to 5 HTTP URLs. Each endpoint is checked every 5 minutes from our probes hosted in the European Union. On every check, we record the HTTP code, latency in milliseconds, and the content of any critical headers (Cache-Control, X-Robots-Tag). If an abnormal response is detected, you receive an instant email alert.

Typical HTTP monitoring use cases

• Watch a homepage: detect an application crash or a hosting outage before your visitors do.
• Monitor a public API: confirm that a REST endpoint returns a 200 code and a valid payload.
• Track a payment funnel: make sure the checkout page stays reachable 24/7.
• Audit a corporate site: prevent SEO traffic loss caused by prolonged 5xx errors.
• Cover a migration: during a hosting change or a deployment, watch for regressions.
• Protect a landing page: detect downtime within minutes before launching a marketing campaign.

The standard English term is website uptime monitoring or http monitoring. The historical players (UptimeRobot, Pingdom, StatusCake, BetterStack) have offered this service for over 15 years. CaptainDNS brings a European approach, integrated into a broader DNS and email ecosystem.

How the CaptainDNS HTTP monitoring tool works

Our tool runs an HTTP check every 5 minutes on each of your monitors. Here is what happens on every check:

1. DNS resolution

CaptainDNS first resolves the URL hostname through our internal DNS resolvers. DNS latency is measured and recorded separately. If resolution fails (NXDOMAIN, SERVFAIL, timeout), the check is marked as dns_error and an alert is triggered.

2. TCP handshake and TLS negotiation

A TCP connection opens to the resolved IP. For HTTPS URLs, a TLS handshake is negotiated. CaptainDNS validates the certificate chain, the expiration, and the hostname match. An expired or invalid certificate triggers a tls_invalid alert.

3. HTTP request and response read

An HTTP request (GET by default, or the configured method) is sent. CaptainDNS waits for the response for up to 30 seconds. Beyond that, the check is marked as timeout. The HTTP code, headers, and total latency are recorded.

4. Evaluating the check result

By default, CaptainDNS marks a check as up if the HTTP code falls in the 200-399 range. You can customize the expected codes (for example only 200 and 301). A 5xx code, a timeout, or a network error marks the check as down.

5. Storage and alerting

The result is stored in the database for 30 days. If the monitor state flips from up to down, an email alert is sent immediately. When the state returns to up, a recovery email is sent to close the incident.

Check regions: Europe first

CaptainDNS probes are hosted in France and Germany. This guarantees latency close to what your European users experience and full GDPR alignment. No check data ever leaves the European Union.

Real-time email alerts when your site goes down

Alerting is the heart of any monitoring tool. CaptainDNS sends an email alert the moment a check fails, with minimal friction and zero spam.

Trigger conditions

Built-in anti-spam

Without precaution, a flapping site (alternating up/down) can generate dozens of alerts per hour. CaptainDNS applies three mechanisms to avoid this:

1. Two-check confirmation: before sending an alert, CaptainDNS runs a second immediate check from a different probe. If both fail, the alert is sent. This eliminates false positives caused by local network incidents.
2. Per-incident grouping: during continuous downtime, only one alert is sent at the start. No interim alerts as long as the site stays down. A recovery alert is sent when the site comes back up.
3. Auto-disable: if a URL stays down for more than 7 consecutive days, CaptainDNS sends a warning email and automatically disables the monitor. You avoid receiving alerts on URLs that are permanently dead.

Alert email format

The email contains the strict minimum needed to understand the incident:

• URL involved
• HTTP code or error type
• Latency of the last successful check
• UTC timestamp and local time
• Direct link to the dashboard to rerun a manual check

No image tracking, no marketing pixel, no third-party tracker links. The email is minimal and functional.

Uptime metrics, p95 latency, and 30-day heatmap

The dashboard aggregates your checks into clear visual metrics. No cluttered charts, no paywall on the essentials.

Core metrics

The p95 latency is the right indicator of perceived performance. The average hides spikes, while p95 tells you what your users experience in the worst 5% of cases.

30-day heatmap

The heatmap visualizes the last 30 days as a colored grid. Each cell represents a time window (1 hour or 1 day depending on zoom):

• Green: every check in the window succeeded
• Orange: a few checks failed (brief incident or flapping)
• Red: most checks failed (long incident)
• Gray: no data (monitor disabled or not yet created)

A single glance is enough to spot problematic periods and correlate them with an application change. The heatmap is free and unlimited, unlike several competitors who reserve it for paid plans.

Detailed history

Every individual check can be reviewed for 30 days: timestamp, HTTP code, DNS latency, TLS latency, total latency, response headers. You can filter by status (up only, down only, TLS errors) or by date range to debug a specific incident.

Comparison of website monitoring tools

Here is how CaptainDNS positions itself against the main website monitoring tools (UptimeRobot, BetterStack, Pingdom).

Unique CaptainDNS advantages

1. Unified stack: a single login to manage DNS, SPF/DKIM/DMARC, email blacklist monitoring, TLS certificates, and HTTP uptime. Specialized players force you to juggle 4 or 5 tools.
2. Made in EU with no compromise: probes in France and Germany, database in France, team based in Europe. No transfer to the United States, no Cloud Act exposure.
3. No artificial paywall: the heatmap, p95 latency, and 30-day history are included in the free plan. Most competitors lock these behind $15 or more per month.
4. Smart auto-disable: no other tool offers this mechanism. You avoid noise on permanently dead URLs.

When another tool still makes sense

UptimeRobot remains unbeatable if you need to monitor more than 50 URLs on a free plan. BetterStack excels at advanced status pages with strong branding. Pingdom is interesting for very large companies already paying for the SolarWinds suite.

CaptainDNS targets developers, freelancers, agencies, and European SMBs that want a simple, free, GDPR-compliant tool integrated into their DNS and email stack.

Quotas, limits, and free plan

CaptainDNS practices full transparency on quotas. No fine print, no surprises.

Free plan

• 5 simultaneous HTTP monitors
• Check every 5 minutes (288 checks per day per monitor)
• Unlimited email alerts to a recipient address
• Full 30-day heatmap
• 30-day history of individual checks
• Public API to retrieve your results
• No credit card required

Cases not covered by the free plan

• Raw TCP monitoring on non-HTTP ports (SMTP, FTP, database)
• Multi-step transactions (user journey across several pages with assertions)
• Probes outside the EU (Asia, Americas, Oceania)
• Status pages with a custom domain (status.captaindns.com)
• Slack, Discord, PagerDuty, or Opsgenie alerts

If you need these features, paid plans will be offered later. No aggressive upsell attempts in the free dashboard.

Why 5 monitors and not 50?

The free plan must remain financially sustainable. A check every 5 minutes represents around 8,600 HTTP requests per month per monitor. With 5 monitors per free account, the infrastructure cost stays manageable while still covering the real needs of a freelancer or a small team (homepage, API, payment page, blog, customer dashboard).

If your need exceeds 5 monitors, contact us to discuss a custom plan or an extended quota for open source and nonprofit projects.

European hosting and data sovereignty

HTTP monitoring is a data processing activity: you send URLs, optional headers, and sometimes authentication tokens. GDPR applies as soon as an end user is identifiable or the processing concerns a European service.

EU hosting and processing

CaptainDNS operates from the European Union:

• HTTP probes in France and Germany
• PostgreSQL database in France
• Backups in France, with no transfer outside the EU
• Technical team based in Europe

No monitoring data crosses the Atlantic. The US Cloud Act does not apply. The risk of an injunction from a third-party authority is zero.

No tracking cookies

The CaptainDNS dashboard uses no tracking cookies, no marketing pixels, and no third-party analytics scripts. Authentication runs on Auth0 hosted in the EU. The only data recorded is what is strictly required for the service: your email, your monitors, and your check results.

Comparison with competitors based outside the EU

UptimeRobot, Pingdom, BetterStack, and StatusCake host their data in the United States or the United Kingdom. Even when these players offer a DPA addendum, their probes often remain located outside the EU and their subprocessors (AWS US, GCP US) fall under the Cloud Act. For strictly European processing, CaptainDNS is the simplest option.

Logs and retention

Individual checks are kept for 30 days, then automatically deleted. Aggregated metrics (monthly uptime, average latency) are kept for 12 months. You can delete a monitor at any time, which wipes all its associated data within 24 hours.

Compliant by default

No consent to collect from your users: monitoring is an internal processing activity for which you are the data controller. CaptainDNS acts as a processor under article 28 of GDPR. The DPA is available on request.

Frequently asked questions about monitoring

Q: What is website monitoring?

A: Website monitoring is the practice of continuously checking the availability, latency, and integrity of an HTTP URL. A monitoring tool sends a request at a regular interval (for example every 5 minutes), records the response, and triggers an alert on failure. This lets you catch an outage before your users do.

Q: How often does CaptainDNS check my URL?

A: By default, CaptainDNS runs an HTTP check every 5 minutes on each of your monitors. You can customize the frequency with a cron expression for advanced scenarios (check every minute during business hours, exclude a maintenance window, and so on).

Q: How do I receive an alert when my site goes down?

A: When you create the monitor, set a recipient email address. The moment a check fails (5xx code, timeout, DNS error, invalid TLS certificate), you get a real-time email alert. CaptainDNS groups alerts to avoid flooding your inbox.

Q: What does 99.9% uptime mean?

A: 99.9% uptime means your service is available 99.9% of the time, which translates to roughly 8 hours and 45 minutes of maximum downtime per year (43 minutes per month). It is the standard threshold for a production site. At 99.99%, you drop to 52 minutes of downtime per year.

Q: Is CaptainDNS free for monitoring my site?

A: Yes. The free plan includes 5 HTTP monitors with checks every 5 minutes, unlimited email alerts, a 30-day heatmap, and p95 latency. No credit card required at sign-up, no limited trial period.

Q: What is the difference between CaptainDNS and UptimeRobot?

A: CaptainDNS combines DNS, SPF, DKIM, DMARC, blacklists, and HTTP monitoring in a single dashboard, hosted in the EU and GDPR compliant. UptimeRobot only does uptime monitoring and stores its data in the United States. CaptainDNS offers 5 free monitors, compared to 50 on UptimeRobot but with a check every 5 minutes (identical to the UptimeRobot free plan).

Q: Can I monitor an authenticated URL or a private endpoint?

A: Yes for public URLs reachable from the internet. CaptainDNS supports custom HTTP headers (Authorization, X-API-Key) to query token-protected endpoints. URLs behind a VPN or a private firewall are not reachable from our probes.

Q: How do I share my monitoring results?

A: CaptainDNS offers an integration with public status pages. Link your HTTP monitor to a public status page to expose uptime, latency, and incident history to your users or customers without giving them access to your private dashboard.

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