Website monitoring that catches
what uptime tools miss.
website issue monitoring
Visual Sentinel checks your pages like a visitor: uptime, SSL, DNS, speed, content, and visual changes. Get alerted when a page goes down, slows down, or looks wrong.
What is website monitoring?
Website monitoring is the practice of automatically and continuously checking a website to verify it is online, fast, reachable, and visually correct. A modern website monitoring tool runs scheduled checks from one or more regions, captures evidence (response times, screenshots, content snapshots, certificate health), compares each result against a known baseline, and alerts the right people when something deviates.
The phrase covers a range of intent. Uptime monitoring is the cheapest version: a single check that the URL responds successfully. 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.
Choosing between monitoring approaches? Compare website monitoring tools and coverage before you choose a plan.
Monitor your website from outside your own stack.
Whatever you monitor, the checks have to run from infrastructure that is not your hosting. A cron job or health-check script on the same server dies with the server, so the most common monitoring failure for a single site is a monitor that cannot send the alert because it went down with the thing it was watching.
An external check also exercises the full visitor path: DNS resolution, TLS negotiation, CDN edges, firewall rules and routing. Your origin can be healthy while an expired certificate, a bad DNS change or a misconfigured proxy rule makes the site unreachable for everyone else. Visual Sentinel checks your public URL from EU and US nodes, and when one region fails while the other succeeds, the alert says the problem is regional rather than a full outage.
Every important signal.
One monitor.
Uptime, SSL, DNS, speed, content, and visual checks work together so you can see what changed and where to look first.
Uptime
HTTP, HTTPS, ping, port, and TCP checks with plan minimums of 10 minutes on Free, 5 minutes on Solo and Starter, or 1 minute on Business and Agency. Slower schedules are configurable.
Performance
Regional response timing follows the uptime schedule, with detailed network phases when available. Paid monitors also receive a daily mobile Lighthouse lab result.
SSL & TLS
HTTPS checks validate the served certificate and hostname, while certificate history records issuer, validity dates, SANs, fingerprint, algorithm, and key size. Default expiry warnings are 13, 3, and 1 days, with 20 and 6 days optional.
DNS
Selected A, AAAA, MX, NS, TXT, and CNAME records are snapshotted every six hours on Solo and higher. A changed snapshot records the before-and-after values; Cloudflare-integrated customers can also retain observed origin data when available.
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 for configured public-page elements on Starter and higher. Track selected copy, calls to action, prices, or freshness rules on the monitor interval. The worker reads source HTML and does not execute page JavaScript.
Need text-level evidence for prices, calls to action, legal copy, or injected spam? See website content monitoring.
A page can be reachable
and still fail the customer.
A reachable page can still be broken
A basic uptime check says the URL responded. It does not prove the page rendered correctly, TLS is trusted for the hostname, selected DNS values match the prior snapshot, or the layout is intact. Visual Sentinel can collect those distinct signals on their plan-specific schedules.
Single-region checks miss real outages
A single location cannot distinguish a regional path problem from a global outage. Visual Sentinel runs uptime checks from EU and US nodes and uses cross-region confirmation before treating a single-node failure as a confirmed outage.
Broken visuals lose revenue quietly
A failed deployment that produces a blank checkout page, a third-party script that distorts the homepage, or a payment widget that fails to render can go unnoticed by basic uptime checks. A scheduled visual capture can record the rendered difference against its baseline.
Alert fatigue kills monitoring tools
A monitor that pages you for every flake gets muted. Visual Sentinel uses cross-region confirmation, configurable retry counts, alert delays, deduplication windows, and per-monitor routing to reduce repeated or unconfirmed notifications.
The pipeline,
start to finish.
- Schedule.
Each enabled layer follows its own plan boundary: uptime and TLS run every 10, 5, or 1 minute; DNS every six hours; visual every 30 or 15 minutes; configured content uses the uptime interval.
- Fetch.
Uptime checks use EU and US nodes with cross-region confirmation. Browser captures, DNS history, mobile Lighthouse lab runs, and server reports use separate workers and evidence paths.
- Evaluate.
Each worker evaluates only its supported evidence, such as status and timing, TLS trust and leaf expiry, selected DNS values, screenshot differences, or configured text.
- Persist.
Relevant results, baselines, snapshots, and daily summaries are retained according to the plan and evidence type.
- Alert.
A confirmed result that violates the configured rules enters the routed notification workflow. Delay, retry, deduplication, and channel settings affect delivery.
- Recover.
Applicable incident types can auto-resolve after the required recovery evidence, with recovery notifications sent through eligible configured channels.
Try it without signing up.
One-shot checks against any URL or domain.
Website status checker
HTTP status, response time, server header, basic SSL state.
SSL certificate checker
Expiry date and days left, chain completeness, hostname match, issuer, and TLS version.
DNS propagation checker
See which public resolvers return a record, with TTL, or look up every record for a domain.
Page speed test
Mobile Lighthouse lab score with LCP, FCP, CLS, TTFB, Total Blocking Time, and Speed Index.
Three free monitors cover
most side projects.
Solo developers and indie hackers
Three free monitors with uptime and SSL checks cover a personal blog, portfolio, or side project. Catch breakage before your first users do.
Small businesses with one critical site
Spot visible storefront problems, such as a missing payment button or a shifted layout, with paid visual checks. Eligible plans can route alerts to WhatsApp. A screenshot check does not test whether a payment completes.
Agencies and consultancies
Monitor every client site with whitelabel status pages, per-client alert routing, and a single billing relationship at the Agency tier.
Answers,
in plain English.
Can't find what you're looking for? Email support.
Planning a visual monitoring evaluation? Follow the baseline, change and recovery checklist.
Start monitoring,
then unlock more when needed.
start watching in 60 secondsFree covers three uptime and SSL monitors with email and push alerts. Paid coverage starts at $15/month with a 10-day card trial for an eligible workspace.