4 regions listening right now
Is it down, or is it
just you?
Type a URL and Sentinel checks it live from 4 regions on three continents, timing every step from DNS to first byte. No account needed.
The check
One check,
four questions.
The timing bar you just ran isn't decoration. Each segment is a question your site has to answer before a visitor sees anything at all.
Can the world find you?
dnsName resolution is the first thing to fail when a registrar lapses, a record changes, or a nameserver misbehaves.
Can anyone connect?
tcpA dead server, a firewall change, a full disk: connections get refused long before anyone sees an error page.
Is the handshake trusted?
tlsAn expired or misconfigured certificate turns every visitor away at the door, with a warning that looks like a hack.
Is the app actually alive?
ttfbTime to first byte is where slow databases, hung workers, and overloaded servers hide.
Sentinel asks these questions about your monitors around the clock, from every region, and wakes you only when an answer changes.
Uptime & website monitoring
Everything that breaks, watched.
Uptime is just the loudest failure. Sentinel watches the quiet ones too: the certificate, the DNS record, the cron job nobody thinks about.
http
Uptime monitoring
Checks as often as every 30 seconds from every region, with consensus across regions before an alert fires. No false alarms from one bad vantage point.
tls
SSL certificates
Alerts weeks before a certificate expires, and the moment a chain stops validating.
dns
DNS records
Seven record types watched. Know the instant something changes.
whois
Domain expiry
Registration dates tracked, with alerts well before a client's domain lapses.
json
API monitoring
Send custom requests and assert on the JSON that comes back. Catch the broken API hiding behind a 200 OK.
cron
Heartbeats & cron
A dead man's switch for scheduled jobs: your backup script or queue worker pings us after each run, and a missing ping opens an incident. Silence becomes a signal.
icmp
Ping
Echo from every region for servers and devices that don't speak HTTP.
tcp
Port checks
Connection checks for databases, mail, SSH, and anything listening on a port.
html
Keywords
Verify content exists, or catch errors and defacements the moment they appear.
public
Status pages
Branded pages, public or password-protected, so clients check uptime themselves.
timeline
Incidents
Automatic timelines and resolution notes for smoother client updates.
mcp
AI assistant
Connect Claude, ChatGPT, or any MCP agent. Ask "is anything down?" in plain language.
For agencies & freelancers
Built for people who answer to clients.
The worst way to learn a client's site is down is from the client. Sentinel makes you the one who breaks the news, with the fix already underway.
Onboard your first client siteBranded status pages
Public or password-protectedClients check uptime themselves instead of emailing you at 7am.
See a live demo →Scheduled uptime reports
On a scheduleProof that the retainer is working, delivered without you lifting a finger.
Incident timelines
AutomaticWhat broke, when, and what fixed it: ready to paste into the client update.
Team seats & roles
Role-basedDevelopers and account managers see what they need, and nothing they don't.
"It is by far the best monitor I've ever used. I could not recommend this product more."
Sentinel has been reliable and easy to use for monitoring my website. I receive notifications as soon as my site goes down and when it's back online, and the reporting, status pages, SSL monitoring, and diagnostic tools make it a complete website monitoring solution. The distributed monitoring servers across the US, Europe, and Asia also give me confidence that outages are detected from multiple locations.
This is an essential tool for anyone who values their online presence. Sentinel gives me peace of mind with the assurance that I'm first to know about any website issues.
Pricing
Plain pricing.
The free plan needs no card. Paid plans start with a 14-day trial, and you can cancel anytime.
Business
$59/mo
For growing agencies with advanced client reporting.
Up to 300 monitors
Choose BusinessFAQ
Fair questions.
What is Sentinel?
Sentinel is a website and infrastructure monitoring tool built for agencies and freelancers. It watches your clients' sites around the clock and alerts you the moment something goes down, so you can fix issues before clients notice.
What can Sentinel monitor?
Uptime, SSL certificates, DNS records, domain expiration, page keywords, JSON/API responses, ICMP ping, TCP ports, and heartbeat/cron jobs. You can watch everything that keeps a client site online from a single dashboard.
How quickly will I know when a site goes down?
Checks run as often as every 30 seconds from four global regions, and an outage is confirmed by consensus across regions before you're alerted. That means you usually hear about downtime before your client does, without false alarms from a single bad region.
How does Sentinel alert me?
Alerts can be sent via email, SMS, Slack, Discord, Microsoft Teams, and webhooks, so notifications land wherever your team already works. You control which channels and severities fire for each monitor.
Who is Sentinel for?
It's designed for digital agencies, freelance developers and designers, and SaaS teams who manage one or many sites and need to prove uptime to clients or customers.
Can I give clients their own status page and reports?
Yes. You can publish branded status pages so clients can check uptime themselves, and send scheduled uptime reports that demonstrate the value of your retainer or care plan.
Is there a free plan or a free trial?
Yes. There's a free plan you can start on with no credit card, and paid plans include a 14-day free trial. You can cancel anytime.
How long does it take to set up?
About 60 seconds per monitor. There's nothing to install, just enter a URL, pick how often to check, and choose where alerts should go.
Downtime won't wait for business hours.
Set up your first monitor in about 60 seconds. Be the one who breaks the news, not the one who hears it.
your session · 00:00:00 · 100.000% uptime