Built for agencies looking after many client sites, on any platform. The client report is the product. The monitoring engine exists to feed it.
Every monitored site produces a white-label report on the schedule the agency chooses. Their logo, their accent color, their reply-to, their agency name as the sender, and, once they verify a domain they own, their own sending address. The report body is theirs. SiteLetter does the work in the background.
Plus a broken-link sweep in the report, SSL and domain expiry once Renewals is switched on for that site, and a portfolio overview across all client sites in the dashboard.
acme-client.com · 12 pages · 2026-09-21 - 2026-09-27
Checked 12 pages - 2 meaningful changes
Hero image area is blank - broken image placeholder visible.
Hero copy rewritten and a new testimonial card added.
Assembled from parts, this job is a Frankenstein stack. UptimeRobot pings the homepage. A Lighthouse runner spits out scores into a folder no one opens. A screenshot tool fires off cron jobs. And once a month, somebody on the team copy-pastes all of it into a Google Doc with the client's logo on top.
That document is where SiteLetter starts. Between the kickoff and the renewal call it is the piece of the work a client can actually hold, so it is the product, and the monitoring engine is the thing that feeds it. Everything else is plumbing.
SiteLetter isn't trying to be the best fit for a fintech SRE team. It's trying to be the obvious choice for the agency looking after many client sites, on any platform, and billing a monthly retainer. See how it compares to Oh Dear, UptimeRobot, BetterStack, Checkly, and the rest.
Feature requests that pull SiteLetter away from agencies looking after many client sites get turned down. If your team writes its monitoring as code and deploys it through the same pipeline as the app, you'll be happier with Checkly.
Pricing is on the pricing page. Signing up is self-serve. The contact form goes to a real person, who usually replies within one business day.
Every comparison page has a "where the other tool wins" section, with the strengths named. If a competitor is the better fit, the comparison page will tell you.
I've been a web developer for about ten years now.
I built SiteLetter because the gap in this category is sharp: most of the uptime and developer-focused tools I compared were built for SREs running production infrastructure, then had a "reports" tab bolted on later. In those tools the agency was a workaround. SiteLetter is the version where the agency is the customer.
SiteLetter started as a way to check whether my wife's site was up. Then I wanted Lighthouse on it. Then visual change detection. Then a weekly email so I'd stop refreshing the dashboard. The product spiraled out of that. I still run it on her site every day, and that's the first place a real bug surfaces.