The Sentinel blog
Notes on website monitoring, security practice, and the unglamorous work of keeping things online.
PHP warnings above a WordPress header, stack traces from a failed deploy, database errors in the response: Sentinel now detects server-side errors automatically during normal HTTP monitoring, with no keywords to configure or maintain.
"My hosting company already monitors my site" is half true. The host watches its infrastructure, for its own SLA, from inside its own network. Expired certs, broken checkouts, DNS mistakes, and the question of who finds out first are all outside that scope.
Every incident starts with the same question: did we just ship? Deploy markers draw the answer directly on the response-time chart, cite deploys beside incidents, and can pause monitoring while a deployment runs.
Slack is a business signal and Discord is a hobbyist signal, so gating Discord monetized nobody. The reasoning behind the pricing change, and what the free plan includes now.
Our Slack app asks for one scope. Our GitHub app holds no credentials at all. Why minimal permissions shaped what got built, what that constraint costs, and why the consent screen is part of the product.
A status code tells you the server answered, not that it answered with your website. Why managed hosts serve error pages at 200, and why a keyword check that asserts your headline is present beats one that hunts for the word "error".
Alerts tell you when something changes. They cannot tell you that nothing has, which is the failure agencies actually fear. Why passive awareness beats another dashboard, and where a menu bar app fits.
AI can write your app in an afternoon, but it won't tell you when it's down. Why vibe-coded apps need uptime, SSL, and heartbeat monitoring, and how to add it in minutes.
Since a November 2024 ToS change, UptimeRobot's free plan is for non-commercial use only. If you monitor client sites on it, here's what that means and your options.
Freshping shut down in March 2026. Here are honest alternatives (Uptime Kuma, UptimeRobot, HetrixTools, and Sentinel) compared for freelancers and agencies monitoring client sites.
Sentinel's monitoring crawler is listed in Cloudflare's Radar bots directory. What SentinelBot does, what verification means for false "down" alerts on Cloudflare-protected sites, and how site owners stay in control.
The three pricing models for website maintenance, typical 2026 retainer ranges by tier, and why the most persuasive price is anchored to what downtime costs the client, not what the work costs you.
Three copy-paste email templates for client outages: the fast initial notification, the mid-incident update, and the all-clear wrap-up that turns a bad afternoon into renewed trust.
A copyable seven-section structure for monthly client uptime reports, plus the three rules that make them land: send them even when nothing happened, use real numbers, automate the data.
Sentinel is listed in the official MCP Registry as io.rootstuff/sentinel: a verified, first-party server that lets Claude, ChatGPT, and any MCP client operate your monitoring in plain language.
Most hacked websites don't look hacked. The nine warning signs of a compromised site, how to confirm it, what to do right now, and the external checks that catch the next one in minutes.
What website defacement is (from full page takeovers to hidden spam and cloaked redirects), why detection speed decides the damage, and how to set up content checks that catch it fast.
The domain expiration timeline stage by stage, why a dropped domain is a security incident and not just an outage, and the monitoring layer that catches silent auto-renew failures.
The best open-source uptime monitoring tools in 2026: Uptime Kuma, Gatus and more, what they do well, and the honest cost of self-hosting before you commit.
Why an API changes what monitoring can do, what to look for, and the new layer: MCP, which lets AI assistants like Claude and ChatGPT query your monitoring in plain language.
How to find genuinely affordable uptime monitoring: the pricing models that stay cheap, the hidden costs that make "cheap" expensive, and how the budget options really compare.
Looking for a Pingdom alternative? Why teams switch, the criteria that actually decide the right tool, and how the main alternatives compare for free trackers, dev platforms and agencies.
Outgrowing UptimeRobot? Why teams move on, the criteria that actually matter, and how the main alternatives compare across free trackers, developer platforms and agency tools.
Skip the rankings. What a status page is really for, the criteria that decide the right tool, the three categories of status page software, and what to test before you commit.
Shopify being up does not mean your store is working. Why Shopify stores still go down, what to actually monitor beyond the homepage, and how to catch problems before they cost sales.
Skip the cookie-cutter rankings. The criteria and categories that actually decide the best uptime monitoring tool for you, from free trackers to agency platforms, plus how the popular names compare.
What free uptime monitoring actually covers, where free plans draw the line, how to set up solid monitoring without paying, and when upgrading finally earns its keep.
A practical, step-by-step guide to setting up website uptime monitoring: what to monitor, how often to check, where to check from, alerts that don't cry wolf, and how to prove uptime.
The criteria that actually matter when an agency picks a monitoring tool: multi-client organization, alert routing, white-label branding, reporting, check types and a pricing model that scales.
A repeatable, twenty-minute checklist for adding every new client to monitoring: what to gather, which monitors to add, naming and tagging, alert routing, status pages and the email that proves your value.
Turn monitoring from an invisible cost into a branded, billable service: branded status pages on custom domains, white-labeled client reports, on-brand alerting, and the economics of reselling it.
A practical guide to API monitoring: what to check beyond a 200, how to assert JSON payloads, alerting that doesn't cry wolf, and when synthetic flows beat single endpoints.
What 99%, 99.9%, 99.99% and 99.999% uptime actually translate to in real downtime, plus how SLAs are calculated and what's realistic to promise clients.
Synthetic monitoring and real user monitoring (RUM) sound similar but answer different questions. What each one does, where each one fails, and which you need first.
Everything you need to know about uptime monitoring in 2026: the five check types, KPIs that matter, alert strategies that don't cry wolf, and how to pick the right tool.
Why single-region monitoring misses real outages, how multi-region checks catch regional failures, and what to look for in a global uptime tool.
A clear breakdown of website monitoring pricing models, what drives cost, sample budgets for 5, 50, and 500 sites, and when paid plans pay for themselves.
Learn how to monitor dozens or hundreds of websites from a single dashboard with organized alerts, team permissions, and per-client status pages.
10 actionable strategies to reduce website downtime, from external monitoring and DNS redundancy to staging environments and incident runbooks.
A step-by-step guide to building website care plans with tiered pricing, monitoring, reporting, and strategies that turn maintenance into recurring revenue.
A practical guide to WordPress uptime monitoring: why WP sites go down, what to monitor, and how to set up external checks that catch real problems.
A non-technical, step-by-step guide to diagnosing why your website is down, what to do right now, and how to stop it being a surprise next time.
A practical monitoring playbook for freelance web developers: minimum viable stack, alert triage, a 30-minute setup, and how to charge for uptime.
Learn how to define uptime guarantees, set realistic targets, and use monitoring data to back up your SLA commitments to clients.
Learn how to calculate the true cost of website downtime, including hidden costs like SEO damage, lost trust, and wasted ad spend.
A complete guide to managing client sites with centralized monitoring, smart alerting, status pages, and uptime reports.
Set up a status page that builds trust, reduces support tickets, and keeps clients informed during incidents.
Discover what happens when SSL certificates expire and how automated monitoring prevents certificate-related outages.
Everything you need to know about uptime monitoring: how it works, why check intervals matter, and how to set it up in 60 seconds.
Learn how DNS monitoring works, what records to watch, and how to protect your domain from hijacking and unauthorized changes.
A practical guide to the incident lifecycle, escalation workflows, and reducing mean time to resolution for web teams.
Seven practical best practices for agencies, from multi-region checks to CI/CD integration and smart alerting strategies.
Set up your first monitor in about 60 seconds and let us do the watching.