How to Monitor Client Websites: Agency Uptime Guide

If you build or maintain websites for clients, you already know the worst way to learn a site is down: a message from the client asking why their homepage won't load. Learning how to monitor client websites properly fixes that. You hear about the problem first, you fix it sooner, and you reply with "we spotted it and we're already on it" instead of an apology.

This guide is for web agencies, freelancers, and anyone looking after more than a handful of sites. It covers what to monitor on each client site, how to keep dozens of monitors organized, how to route alerts so the right person sees them, and how to turn monitoring into part of your care plan.

Why agencies need to monitor client websites differently

Watching one website is simple. You add a check for the homepage and you're done. Watching 20, 50, or 150 client sites is a different job:

You didn't build all of them. Some came from other developers, with themes, plugins, and integrations you've never touched.
You don't control the hosting. One client is on managed hosting, another is on cheap shared hosting, and a third insists on their cousin's VPS.
Every site matters to someone. A brochure site going down at 3 a.m. is annoying. A client's booking form failing on a Saturday morning is a phone call.
Your reputation is on the line. The client doesn't care whose server failed. They care whether you knew.

That last point is the real reason to set up uptime monitoring for agencies. The monitor isn't only a technical tool. It's how you look reliable. When you contact a client about an issue before they've noticed it, you stop being the person who broke something and become the person who's always watching.

If you're still not sure how much an outage costs a business, our breakdown of the real cost of website downtime runs the numbers.

What to monitor on every client website

You don't need dozens of checks per site. Most agencies get the best results from two to five monitors per client, focused on the pages and endpoints that make the client money or generate leads.

1. The homepage

This is the baseline. If the homepage returns an error or times out, something is seriously wrong. Each check records the status code and response time, so you can tell a timeout from a 500 error or a 503 from an overloaded server. If you need a refresher, see our guide to HTTP status codes.

2. The page that makes money

For most clients that's one of these:

A contact or quote form for a service business
A booking page for salons, clinics, and restaurants
A checkout or cart page for an online store
A login or member area for membership sites

Monitor that URL separately. A homepage can load fine while the checkout throws an error, and the checkout is the page the client actually cares about.

3. Key API endpoints

Many client sites depend on an API, whether it's their own backend, a headless CMS, or a payment or booking integration. ismysiteup can monitor API endpoints as well as pages, and endpoint tests let you define what "healthy" means: a specific status code, a response under a set time, or a value present in the JSON response. Our post on why an HTTP 200 isn't always healthy explains why that matters.

4. SSL certificates and domain names

An expired SSL certificate or a lapsed domain takes a site offline just as surely as a server crash, and both are completely preventable. ismysiteup flags SSL certificate expiry and domain-name expiry early, with reminders in the days and hours before a domain lapses. That's especially useful for agencies, because clients often own their domains and forget to renew them. Read more about SSL certificate expiry outages.

5. "Up but broken" failures

Sometimes a site returns 200 OK while the business quietly stops working. Orders drop to zero because a payment integration broke, or sign-ups stall because a form stopped submitting. A plain uptime check won't catch that.

ismysiteup's Data Monitors watch a value in a JSON response, such as an order count, sign-ups, or queue depth, and alert you when it stalls or moves the wrong way. If you manage stores or SaaS products for clients, one Data Monitor on the right number can catch problems that no uptime check would.

How to organize monitoring across many client sites

The difference between useful monitoring and alert chaos is organization. Here's a structure that scales.

Group monitors by client or project

In ismysiteup, you can group monitors by client or project and see everything from one dashboard. Create one group per client and put all of that client's monitors in it: homepage, forms, API, and so on. When an alert arrives, you know straight away whose site it is.

Use clear, consistent monitor names

A name like Site 14 doesn't help anyone at 2 a.m. Use a pattern that tells you the client, the site, and the page:

Acme Dental: Homepage
Acme Dental: Booking form
Northside Bakery: Checkout
Northside Bakery: Orders API

Match check intervals to how critical the site is

Not every site needs the fastest possible interval. On ismysiteup, check frequency depends on your plan:

Plan	Uptime monitors	Check interval	Price
Free	5	Every 5 minutes	$0
Pro	50	Every minute	$9/mo
Business	200	Every 30 seconds	$24/mo

The pricing page describes Business as "for agencies & shops running many sites." See the pricing page for current details and availability. A five-minute interval is fine for a small brochure site, while busy stores and booking systems benefit from faster checks.

Plan your monitor budget

A quick way to estimate how many monitors you need:

List every client site you're responsible for.
Note the two to five URLs that matter most on each one.
Add any API endpoints that are critical to the business.
Add the total, then leave room to grow.

For example, 12 clients with an average of three monitors each comes to 36 monitors. If you hit a plan limit, nothing breaks. Your existing monitors keep running, and you're told which limit you've reached.

Route alerts so the right person sees them

Monitoring only works if someone sees the alert. Email is useful as a record, but it's easy to miss an email alert among newsletters and client threads. That's why ismysiteup sends alerts to WhatsApp, Telegram, Slack, and email on every plan, including Free. Alerts through your own WhatsApp, Telegram, Slack, and SMTP setup are unlimited on every plan.

A setup that works well for agencies:

A shared team channel. Send alerts to a Slack channel your team already watches. Follow the Slack alerts setup guide to connect it in a few minutes.
A phone alert for whoever's responsible. For urgent issues, a message on your phone is hard to ignore. See our guides to WhatsApp website down alerts and Telegram website down alerts. A Telegram group is an easy way for a small team to see the same alert.
Email as the paper trail. Keep email on so you have a record to look back on.

You don't have to worry about a flaky client server spamming your channels. The first alert goes out the moment a check fails, follow-ups are batched while a site is flapping, and you get a recovery message as soon as the site is back.

Not sure which channel suits your team? Compare them in email vs Telegram vs WhatsApp downtime alerts.

What to do when a client site goes down

An alert is the start of the process. Having a simple routine means anyone on your team can respond the same way.

Confirm the outage. Check the site from outside your own network. The free instant checker shows the HTTP status, response time, and SSL details for any URL, with no signup.
Read the status code. A 5xx usually points to the server or application. A timeout often points to hosting or DNS. An SSL error points to the certificate.
Check the usual suspects. Did someone deploy, update a plugin, or change DNS recently? Does the host have an incident on its status page? Our guide Is my website down? walks through the checks.
Tell the client early. A short message such as "We've spotted an issue with your booking page and we're working on it" builds far more trust than silence.
Send a follow-up when it's fixed. Explain what happened in plain language and what you've done to stop it happening again.

Make monitoring part of your care plan

Many agencies offer a monthly website care plan or maintenance plan that covers updates, backups, security, and uptime monitoring. Monitoring is one of the easiest parts of a care plan to explain to a client: "We watch your site around the clock, and if anything goes down, we know first."

A few tips:

Make it visible. Tell clients which pages you monitor and how you're alerted. It's work they would never otherwise see.
Mention the catches. When monitoring helps you fix an expiring certificate or a broken form before it affects visitors, tell the client. Those moments are what justify the plan.
Price for response, not the tool. The monitoring cost is small. What the client pays for is your team noticing and acting quickly.

Client status pages are listed as coming soon on ismysiteup's pricing page, so check the pricing page for the latest.

Frequently asked questions

How many monitors do I need per client website?

For most client sites, two to five monitors is enough: the homepage, the page that makes money (a form, booking page, or checkout), and any critical API endpoint. Add more only for larger sites with several business-critical paths.

How often should I check client websites?

It depends on how critical the site is. A five-minute interval suits most small business sites. Stores, booking systems, and SaaS products benefit from one-minute or 30-second checks, so an outage is caught before many visitors run into it.

What's the easiest way to monitor multiple websites at once?

Use one monitoring tool with all your client sites grouped by client or project, so you can see everything on one dashboard. Send alerts to a shared channel such as Slack or a Telegram group, so nobody has to watch the dashboard all day.

Should agencies charge clients for uptime monitoring?

Most agencies include it in a monthly care or maintenance plan rather than selling it on its own. The value to the client isn't the checks. It's knowing someone will spot and respond to a problem quickly.

Is free uptime monitoring enough for an agency?

It's a good place to start. ismysiteup's Free plan includes five uptime monitors, checks every five minutes, and WhatsApp, Telegram, Slack, and email alerts with no credit card. That's enough to cover a few small clients. As your client list grows, you'll need more monitors and faster checks.

Can I monitor client sites I didn't build?

Yes. Uptime monitoring checks a site from the outside, the same way a visitor reaches it, so you don't need to install anything on the client's server. You only need the URLs. Note that ismysiteup can't monitor private or internal addresses, so the sites need to be publicly reachable.

Start monitoring your client websites today

You don't need a complicated setup to stop finding out about outages from your clients. Add your most important client sites, group them by client, connect the alert channels your team actually reads, and you're covered.

Create your free ismysiteup account with no credit card needed, or check any client site right now with the free instant checker.

How to Monitor Client Websites: A Guide for Agencies