Why are there only five tools on this page?

Because we only write about what we've opened and checked ourselves, on a stated date. A list of twenty tools copied from other lists of twenty tools would be longer and less useful: half the rows would be out of date, and nobody would know which half.

Which free plan is the best?

It depends what you're watching. UptimeRobot's free plan covers fifty uptime monitors, ours covers 5 domains but with all seven watches, Site24x7's covers fifty resources for uptime, and MxToolbox's covers one domain. We compared the real ceilings of each on a page of its own.

Do you need a paid tool for three sites?

Honestly, no. At three sites, the free plan of any vendor on this page is enough, ours included, and there's no reason to pay for anything. The question starts to matter around twenty or thirty domains, when the number of renewal dates to keep outgrows what an occasionally updated spreadsheet can carry.

Comparison

The best domain monitoring tools, and who each one is for

There is no first place. The five tools on this page don't do the same job, and ranking them would be like ranking a stethoscope against a fire alarm. What can be written honestly is which question each one answers better than the others — including when the answer isn't us.

Every fact about a vendor was taken from its public site: 12 September 2026 for UptimeRobot, MxToolbox and Site24x7, 25 August 2026 for Domains Defender. Prices are monthly billing, in the currency shown. We publish DomainVigil: the last row of each table is ours, and you should read it knowing that.

Why “best” means nothing here

Behind the phrase “domain monitoring” there are at least four different risks, and no tool covers them all. The name can expire. The certificate can lapse. DNS can be changed by somebody who told nobody. The site can stop responding. And sending reputation can collapse without anything else moving.

Those five risks don't share a probability, a cost, or a repair time. A site that goes down often comes back on its own within minutes. An expired domain name can sometimes be bought back at a high price, and sometimes not at all. A tool that checks uptime every fifteen seconds but ignores the renewal date protects you beautifully against the least serious risk.

So the right criterion isn't the length of the feature list. It's a simpler and slightly uncomfortable question: what woke you up last time? The table below is arranged around that question.

What you're looking for, and the tool that does it

Read it left to right. If no row describes your situation, the odds are that none of these tools is your answer.

Which tool matches which need, checked in August and September 2026
What you're looking for	The tool	Why that one
Knowing within seconds that a site is down	UptimeRobot	Sixty seconds from their Solo plan up, fifteen on their top plan, a mobile app and alerts by SMS or voice call. Their free plan covers fifty monitors. The full comparison
Understanding why a client's email isn't arriving	MxToolbox	Twenty years on deliverability, a free SuperTool with no account, over a hundred blacklists on their paid plans and aggregated `DMARC` reports. The full comparison
Watching servers, containers and logs	Site24x7	A complete observability suite from $10 a month, thirty-two check locations and replayed browser transactions. The full comparison
A French-speaking service hosted in France	Domains Defender	The service closest to ours, hosted in France, with nine free tools and a browser extension. Checked on 25 August 2026. The full comparison
Watching thirty to a hundred and fifty domains for clients	DomainVigil	Seven watches per domain with no monitors to count, a portfolio sorted by client, and an alert that says what to do. That one is us. The fifty-domain calculation
Paying nothing at all	The free plans	Four of the five vendors have a permanent free plan, and they don't cover the same things at all. What each one really gives

What each one does better than us

One line per vendor, and every one of them is true. We publish one of the five tools on this page: without this block, nothing above it would deserve reading.

UptimeRobot is faster. Fifteen seconds against one minute at best here, and they wake you by SMS or phone call, which we can't do.
MxToolbox sees far wider on email. Over a hundred blacklists against our seven, aggregated DMARC reports, inbox placement testing.
Site24x7 covers a whole infrastructure, with thirty-two check locations and user journeys replayed in a real browser.
Domains Defender is hosted in France, offers a browser extension and an unlimited-domain plan that we don't have.

What we do

One thing only, and doing one thing is the choice we started from, not a stage on the way to something else.

Seven watches on the same domain, counted as one domain: expiry, the certificate, DNS, uptime, blacklists, security headers and scheduled jobs.
A portfolio sorted by client, with a status page for each client — the tool is built for people who look after other people's domains.
An alert that gives the likely cause, a three-step fix and who has to act.
5 domains free forever, then 30 for $15 and 150 for $49 a month.

Four questions to ask before choosing

None of them is about a feature. All four still decide the right tool, and the first one decides almost on its own.

What woke you up last time? An outage, a certificate, an expired domain, mail in the junk folder? Pick the tool that covers that risk, not the one with the longest list.
Are you counting sites or domains? Most tools bill by the monitor, and watching three things on one domain uses three units. This is what makes a bill explode without warning.
Who has to read the alert? You, a developer on the team, or the client? A technical alert sent to a client who can do nothing with it produces a phone call, not a repair.
How long do you need to keep the history? Three months on UptimeRobot's free plan, twelve on Solo, twenty-four on Team. Here, 30 days on free and 365 on Agency. The day a client disputes an outage, that's the line that settles it.

If you remember one thing

Choose the risk first and the tool second. The longest feature list is almost never the right answer: it costs more, it takes more setting up, and it will send you alerts about things you're not responsible for.

And start with a free plan, whichever one. Four of these five vendors offer one, permanently, with no card. A month of real use will teach you more about the right tool than any comparison table, this one included.

If your situation is an agency looking after its clients' domains, that's exactly the case we built DomainVigil for, and the free plan covers 5 domains with no countdown.

Try DomainVigil for free

5 domains free, forever. No card required.

Questions people ask us

Why are there only five tools on this page?: Because we only write about what we've opened and checked ourselves, on a stated date. A list of twenty tools copied from other lists of twenty tools would be longer and less useful: half the rows would be out of date, and nobody would know which half.
Which free plan is the best?: It depends what you're watching. UptimeRobot's free plan covers fifty uptime monitors, ours covers 5 domains but with all seven watches, Site24x7's covers fifty resources for uptime, and MxToolbox's covers one domain. We compared the real ceilings of each on a page of its own.
Do you need a paid tool for three sites?: Honestly, no. At three sites, the free plan of any vendor on this page is enough, ours included, and there's no reason to pay for anything. The question starts to matter around twenty or thirty domains, when the number of renewal dates to keep outgrows what an occasionally updated spreadsheet can carry.