Website monitoring done right. Six layers, one tool.
Visual Sentinel is a website monitoring tool that watches uptime, performance, SSL, DNS, visual integrity, and content correctness on every check. Catch the failures that HTTP 200 status codes hide. Free plan covers one site forever.
Free plan: 1 monitor, all 6 layers, all 11 alert channels, no time limit.
What is website monitoring?
Website monitoring is the practice of automatically and continuously checking a website to verify it is online, fast, secure, and visually correct. A modern website monitoring tool runs scheduled checks from one or more regions, captures evidence (HTTP status codes, response times, screenshots, content snapshots), compares each result against a known baseline, and alerts the right people when something deviates. The goal is to catch failures before customers do.
The phrase covers a range of intent. Uptime monitoring is the cheapest version: a single check that the URL returns a successful HTTP status. Web page monitoring extends that with performance metrics. Full website monitoring (also called six-layer or website observability) adds SSL certificate health, DNS resolution, visual regression, and content change detection. The depth at each layer is what separates a website monitor that catches real problems from one that just confirms a server is on.
The six layers Visual Sentinel checks on every monitor
Each layer runs on every check. Each layer can fire its own alert. Each layer is included in every paid tier with no add-ons.
Uptime
HTTP / HTTPS / PING / PORT / TCP checks at intervals from one minute to one hour, from multiple regions, with cross-region confirmation to suppress local network blips.
Performance
Time-to-first-byte, total load time, transfer size, and Core Web Vitals tracked on every check. Alert when a page degrades past your threshold so you catch slow regressions before customers complain.
SSL
Certificate issuer, validity dates, SAN list, key algorithm, and full chain on every HTTPS check. Configurable expiry warnings (30 / 14 / 7 days). Catch chain misconfigurations and rogue intermediates.
DNS
A, AAAA, MX, NS, TXT, CNAME, and SOA records snapshotted on every check. Detect DNS hijacking, accidental record changes, propagation issues, and expiring nameservers. Cloudflare-integrated customers also see the real origin IP behind the proxy.
Visual
Full-page screenshot on a real Chromium browser, compared pixel by pixel against a baseline. Configurable mismatch threshold so dynamic content (ads, timestamps) does not trigger alerts. Catches CSS regressions, missing images, and injected content.
Content
Text-level diff of page content between checks. Detect defacement, accidental copy deletions, missing call-to-action buttons, and stale caches. Configurable keyword assertions for custom rules.
Why most website monitoring tools miss real failures
Basic uptime monitors run a single HTTP check and return one of two answers: up or down. That works for "is the server on" and nothing else. Modern websites fail in subtler ways.
HTTP 200 lies
A status code says nothing about whether the page rendered, whether the SSL chain is valid, whether the DNS still points where you expected, or whether the layout broke. The cheapest monitoring tools only check the status code. Visual Sentinel checks all six layers on every monitor.
Single-region checks miss real outages
Status checks from a single location flag every regional network blip as a global outage. Visual Sentinel runs checks from multiple regions in parallel and only fires alerts when the failure is confirmed across regions, cutting false positives without losing real-outage detection.
Status code 200 with broken visuals is the worst outage type
A failed deployment that produces a blank checkout page, a third-party script that distorts the homepage, or a payment widget that silently fails to render are not detected by status-code monitoring at all. Visual regression catches them automatically.
Alert fatigue kills monitoring tools
A monitor that pages you for every flake gets muted. Visual Sentinel uses cross-region confirmation, configurable retry counts, time-of-day rules, deduplication windows, and per-monitor alert routing so you only get woken up for real incidents.
How a check runs
- Schedule. Each monitor runs at the configured interval (60 seconds on Business+, configurable down to 5 minutes on lower tiers).
- Fetch from multiple regions. Checks run from US and EU regions in parallel. A single-region failure does not fire an alert until cross-region confirmation completes.
- Evaluate six layers. Status code, response time, SSL chain validity, DNS records, full-page screenshot diff, content text diff. Each is compared against the per-monitor baseline.
- Persist. Every check result is stored. Trends, baselines, and historical reporting all derive from this log.
- Alert with deduplication. A failed check that violates configured rules fires alerts to the routed channels (Email, WhatsApp, Slack, Discord, Telegram, MS Teams, PagerDuty, OpsGenie, webhook, Prometheus). Duplicate alerts inside a configurable window are suppressed.
- Recover automatically. When the next check passes, the incident auto-resolves and a recovery notification fires on the same channels.
Free tools to try right now
No account required. One-shot checks against any URL or domain.
Website status checker
HTTP status, response time, server header, basic SSL state. One-shot.
SSL certificate checker
Issuer, validity dates, SAN list, key algorithm, full chain.
DNS lookup
A, AAAA, MX, NS, TXT, CNAME, and SOA records for any domain.
Page speed test
TTFB, total load time, transfer size, redirect chain.
Who uses Visual Sentinel
Solo developers and indie hackers
One free monitor with all six layers covers a personal blog, portfolio, or side project. Catch breakage before your twelve users do.
Small businesses with one critical site
WhatsApp alerts when your storefront has a broken checkout. Visual regression catches Shopify theme bugs that pass uptime checks.
Agencies and consultancies
Monitor every client site with white-label status pages, per-client alert routing, and a single billing relationship at the Agency tier.
Start monitoring in two minutes.
Free plan covers one monitor with all six layers and all eleven alert channels. Upgrade only when you outgrow it.