The certificate is approaching expiry
The page still loads, but the trust signal underneath it is getting weaker.
Watch website foundationsSelf-hosted website monitoring
Your website can be online and still be broken.
Sentinel watches the promises a website makes: that it responds, redirects, remains indexable, keeps its tags, serves the right sitemap, and has not quietly changed underneath you. When one breaks, Sentinel keeps the evidence and tells the right person.
EXAMPLE CHECK MATRIXWATCH / CHANGE / ACT
HTTP response / 200 OKHEALTHY
Certificate chain / expiryHEALTHY
Canonical URL / expected hostHEALTHY
Robots directive / indexabilityINCIDENT
Sitemap URL inventoryHISTORY
One changed promise becomes an incident with history.
200 OK is not the whole story
Six failures that can hide behind an online page.
The page loads. The promise has changed.
Robots.txt or DNS changed
A small infrastructure edit can alter who reaches the site and where traffic resolves.
Monitor infrastructureSitemap URLs disappeared
The sitemap still exists, but important URLs have quietly fallen out of the inventory.
Check technical SEOA page became noindex or changed canonical
The response is fast; the page is simply no longer making the promise you intended.
Protect indexabilityAnalytics or structured data vanished
The customer-facing page looks normal while measurement or search context has gone missing.
Watch page fieldsContent, redirects, or scripts changed
A deploy can change a critical phrase, redirect policy, security header, or third-party host.
See response checksHow Sentinel works
From changed promise to useful action.
A four-step operating loop.
- 01
Add the targets
Add domains and URLs manually, by CSV, or from sitemaps.
- 02
Choose the promise
Select checks, schedules, request profiles, and alert policy.
- 03
Keep the evidence
Sentinel records runs and rolls contiguous failures into incidents.
- 04
Route the action
Send the right alert and use recovery/history to close the loop.
The current catalogue
Seven families. One place to see the change.
51checks in the current catalogue
Availability and response
1Know whether the page responds, times out, redirects, or returns the status you expect.
SSL, domain, DNS, and email
11Watch certificates, expiry, DNS records, email authentication, and provider fingerprints.
Redirect and indexability policy
7Assert HTTPS, host, 404, geographic redirects, robots fetchability, indexability, and security headers.
Sitemap and URL lifecycle
8Keep sitemap sync, validity, media entries, hreflang relationships, and URL additions or removals visible.
On-page content and metadata
13Protect titles, H1s, content assertions, metadata, canonicals, hreflang, and meaningful content changes.
Analytics, social, and third-party tags
4Notice when analytics, GTM, third-party active-content hosts, or mixed-content resources change.
Bot access and rendered checks
2Probe configured bot categories and, on Pro, use the optional JavaScript worker for rendered checks.
The total is generated from Sentinel’s live check catalogue. Individual checks can still depend on configuration, target behaviour, or an external provider.
Incidents, not alert noise
Keep the failure, the context, and the recovery together.
Sentinel turns contiguous failures into incidents with severity, acknowledgement, recovery, and run history. Quiet hours, digests, maintenance windows, site overrides, and monthly summaries help the operator decide when a signal should interrupt the day.
See alerting and integrationsFor agencies and technical teams
One operating view for every client promise.
Pro adds client access, site grants, outbound channels, white-label controls, custom checks, request profiles, and an optional JavaScript worker. API and MCP surfaces expose scoped monitoring facts for automation.
On hardware you control
Keep the history close to the operation.
The Sentinel appliance combines the Portal app, MariaDB, scheduler, and worker on operator hardware. Configuration and monitoring history live in your database. Optional JavaScript rendering is a Pro worker; sizing guidance stays measured.
Understand the appliance shapeA tier for the operating shape
Start small. Add coverage. Unlock agency depth.
Free
2 domains · 200 URLs
Minimum cadence: daily
Email alerts, run history, incidents, and the core monitoring catalogue.
Plus
5 domains · 1,000 URLs
Minimum cadence: hourly
Email alerts, run history, incidents, and the core monitoring catalogue.
Pro
Agency depthNo vendor-enforced cap domains · No vendor-enforced cap URLs
Minimum cadence: 60 seconds
Client access, outbound webhooks, white-label controls, custom checks, and optional JavaScript rendering.
Every tier includes email alerts. “No vendor-enforced cap” does not mean unlimited physical hardware capacity. Prices are intentionally omitted until issuer plan and checkout values are reconciled.
Questions operators ask
Make the decision with the caveats visible.
Is Sentinel only an uptime monitor?
No. Uptime is one signal. Sentinel also checks infrastructure, redirects, sitemaps, indexability, page fields, content, analytics, third-party resources, and configured bot access.
What runs on my own hardware?
The Sentinel appliance combines the Portal app, MariaDB database, scheduler, and worker on infrastructure you operate. Monitoring configuration and history live in your own database; target requests, notifications, providers, and licence services may still involve third parties.
Can Sentinel monitor JavaScript-rendered pages?
Pro can use an optional JavaScript worker for rendered checks. It is a separate worker path and consumes materially more resources than text-only checking.
How quickly can it check?
Free has a daily minimum cadence, Plus an hourly minimum, and Pro can go as often as every 60 seconds where the individual check permits it. These are cadence floors, not an uptime or detection-time guarantee.
Can an agency give clients access?
Yes, on Pro. Pro supports operator-managed clients, site grants, and related access controls. The operator still decides exactly what each client can see or change.
What happens if a paid licence expires?
The appliance falls back to its normal Free entitlement handling rather than opening a SaaS billing surface. Coverage and cadence may be reduced to the Free limits.
Does “no vendor-enforced cap” mean unlimited hardware capacity?
No. It means Pro has no vendor-enforced licence cap on domains or URLs. Hardware, worker throughput, target behaviour, and configuration still bound practical capacity.