Best Uptime Monitoring Tools

No matter what your website does, it exists to attract the public to your business, cause, or interest. Confusingly, thanks to cache servers and content delivery systems, your site can be available in one part of the world and not in others. Are all of the elements of every page on the site loading successfully? It is impossible to check these issues constantly yourself, so you are going to need an uptime monitoring tool.

The best uptime monitors don’t run on your in-house system – they are strategically located on servers all around the world. Many businesses outsource the hosting of their sites and don’t even know the physical location of those servers. It really doesn’t matter where your website is sent from, it matters that it successfully reaches your full potential audience. Uptime monitoring lets you know when things go wrong.

Here is our list of the best network uptime monitoring software and tools:

  1. Pingdom Synthetic Monitoring EDITOR’S CHOICE An online system that issues automated website performance checks. The service checks your website’s availability, load metrics, and response times from 100 locations. Start a 14-day free trial.
  2. Datadog Synthetic Monitoring (FREE TRIAL) API-driven or browser-based uptime monitoring from multiple locations.
  3. Sematext Synthetics (FREE TRIAL) A testing system that runs performs regular browser-based and HTTP checks on the availability and performance of websites from several locations around the world.
  4. Better Uptime (FREE TRIAL) Availability checker that monitors website uptime from five, globally dispersed locations.
  5. SolarWinds Network Performance Monitor (FREE TRIAL) The industry leader in network monitoring uses SNMP routines to check on the health of network devices. Download a 30-day free trial.
  6. SolarWinds Engineer’s Toolset (FREE TRIAL) A package of more than 60 tools to help you monitor and manage a network.
  7. Site24x7 Website Monitoring (FREE TRIAL) Cloud-based service that monitors website performance, IT infrastructure, and application activities.
  8. Paessler PRTG (FREE TRIAL) An integrated network, server, and application monitor that offers an external website uptime and response time checker. Runs on Windows Server.
  9. Server Density A cloud-based solution that monitors onsite and offsite networks, servers, and applications with additional website uptime checks from multiple locations.
  10. Nagios XI A systems monitoring tool that includes availability monitoring for websites.
  11. ManageEngine OpManager A systems monitor for networks that includes a URL availability for both internet and intranet sites. Installs on Windows Server and Linux.
  12. Zabbix Free, open-source network monitoring system that has a plug-in for monitoring the availability of server farms. Runs on Linux.
  13. ITRS Synthetic Monitoring Launches uptime tests from 180 locations in 60 countries, monitoring availability and response times for each element in a page – not just the site overall.
  14. Icinga 2 A popular, free system monitoring tool that runs on Linux. The server monitoring console of this system can be adapted to watch website uptime.

Uptime monitoring and response time monitoring

Response time monitoring is equally important because a web page that is slow to load or has loading errors in it is the same as being unavailable. The busy online consumer won’t waste time waiting for a slow page to load but will move on to the next entry in the search engine results page – that high bounce rate will not only lose each impatient customer but lower your search engine rankings, making it harder to win customers in the future.

The best uptime monitoring tools

When looking for the best uptime monitoring software and tools, we identified specialist services that focus on website availability monitors and also in-house software that can check your network servers and web services to make sure that they are working correctly.

1. Pingdom Synthetic Monitoring (FREE TRIAL)

Pingdom Synthetic Monitoring Latest Timeline

Pingdom Synthetic Monitoring launches automated checks on the availability of online services and websites from 100 locations around the world. As well as reporting on uptime, this service includes page speed statistics and transaction monitoring to make sure every element of a site is working satisfactorily.

As the tool is based on external servers, there is very little work involved in getting this uptime monitor set up to check on your system performance. The service will monitor your network constantly and register an alert when performance standards slip. Those alerts are shown in the dashboard for the tool, but you can also get them sent to you as SMS or email notification, or through a web API. This means that you don’t have to sit watching the console to catch performance problems.

Pingdom Synthetic Monitoring Site Status

As this service is based remotely, it is specifically aimed at monitoring the availability of websites and other internet services that your company may provide. As well as spotting performance problems, the tool will drill down and explore the causes of your problems.

A Timeline Metrics feature identifies specific elements in a page that are slow to load or completely unavailable, so you don’t just get uptime reports for a page, but for each element, which could be delivered by different services or content delivery networks. A Transaction Monitoring tool in the service performance simulated walk-throughs on a site to spot errors.

Pingdom is charged for on a subscription per month with the rate set depending on the frequency of tests that you choose. You can get a combined 14-day free trial of Pingdom Synthetic Monitoring and Pingdom Real User Monitoring.

Key Features:

  • No software installation required
  • Tests from 100 locations
  • Stored test results
  • Page speed statistics
  • Downtime alerts


Pingdom is our top choice for uptime monitoring because this online service requires no installation and will make repeated checks on your website’s availability from 100 locations worldwide. The alert mechanism in Pingdom lets you assume that your website is available unless you hear otherwise. All website checks are logged and records of test results are available for historical analysis. Pingdom also includes a transaction monitoring service that enables you to confirm that all interactive elements in your site are working properly.

Start 14-day Free Trial:

OS: Cloud-based

2. Datadog Synthetic Monitoring (FREE TRIAL)

Datadog Synthetic Uptime Monitoring

Datadog offers a range of cloud-based system monitoring services, including uptime monitoring tools. The company offers two types of website availability monitoring, which it groups under the category of Synthetic Modelling. Both options test the availability of a website repeatedly from different monitoring locations around the world.

The uptime monitors make checks either through an API or through a browser. In each case, on a subscription basis, charged in units of 1,000 access attempts per month for browser access or 10,000 units per month for API access.

The browser tests are more comprehensive and deliver more detail. They include screenshots of failed access attempts. All tests for both methods are logged and timestamped. The website manager is also able to create custom tests and run them repeatedly through the remote Datadog test agents.

As well as checking the availability of a site and each of its pages, the uptime monitors record response times. The site manager can access the results of tests in a dashboard, which has great visualizations. Failures or poor responses trip performance thresholds, generating alerts. The threshold levels are adjusted through a machine learning process, which accounts for factors, such as internet connection reliability.

Errors can be traced to the cause, whether it is code-based or an infrastructure issue. Log analysis features in the Datadog tool assist in quick identification of the root cause of the problem.

The API version of the uptime monitor from Datadog is considerably cheaper than the browser-based test. They cost $5 per 10,000 tests per month, whereas the browser-based service is priced at $12 per 1,000 tests per month. Datadog offers a 14-day free trial of either system.

Key Features:

  • Browser-based tests
  • API feed option
  • Multiple external test locations
  • Root cause analysis
  • Downtime alerts

Datadog Synthetic Monitoring Start 14-day FREE Trial

3. Sematext Synthetics (FREE TRIAL)

sematext Synthetic Monitoring metrics

Sematext offers infrastructure monitoring from the cloud. The company has created a range of monitors that can each be used as a standalone service. One of the systems that Sematext runs is called Sematext Synthetics. This is a synthetic modeling service that can perform entire run-throughs of a typical visitor journey through a website. This is particularly useful for a new website before it is published or for new features that are to be added to an existing website.

Another use for the Synthetics service is to check on the availability of a website. These uptime monitors can be combined with other tests, such as load time measurements and API statuses. Tests can be performed regularly from servers located in many physical locations around the world. There is also a choice for the user over whether to run browser-based tests or HTTP tests.

Although every run is logged and summarized in graphs available in the system dashboard, it is probably the problems that interest most system administrators. The Sematext tests will carry on, possibly without any interest from the tech team that manages the website. The service raises an alarm should the monitored website become unavailable. This means that the tech team can get on with other tasks and just switch to the web server when unplanned downtime occurs.

As a SaaS system, Sematext Synthetics is charged for by subscription. There are two subscription plans called Standard and Pro with the lowest price available offered by the Standard package at $29 per month. Sematext also offers a Pay-As-you-Go option that costs $2 per HTTP monitor or $7 per browser-based monitor. All three plans are available on a 30-day free trial.

Key Features:

  • Transaction monitoring
  • User journey simulation
  • Multiple test locations

Sematext Synthetics Start 30-day FREE Trial

4. Better Uptime (FREE TRIAL)

Better Uptime Availability Checker

Better Uptime is a website availability monitor that performs periodic checks on a site’s uptime from five locations. These locations are: the USA, Australia, South Africa, American Samoa, and the EU. Tests can be performed with Ping or through a Web browser. You get a choice of browser to run your tests through from Google Chrome, Mozilla Firefox, and Apple Safari.

This system isn’t entirely automated. It is a managed service with human operators manning the testing system. If a target is found to be down, the system retests from two other locations before notifying the customer. This procedure is built into the service in order to prevent false-positive reporting and cut down the number of alerts that the client receives that could be due to a glitch in the Internet connection used for the test.

All tests are logged and a list of each availability check can be inspected in the user dashboard. The console also shows the sequence of test results in a color-coded bar.

A failed contact event gets documented with screenshots of the failure message appearing in a browser. Subscribers get notified when a test fails. These notifications can be implemented by phone call, SMS, email, or Slack message. The operators for the service can be contacted by the client around the clock. There are two operation centers for Better Uptime, which are located in Alabama, USA, and Belgium in Europe.

The tests aren’t only concerned with checking on the availability of Web pages. The user can specify tests to check on the availability of APIs and services that get triggered within pages on a site.

Incidences can be sent straight through to Help Desk software. There is a range of integrations for Better Uptime that enables it to interface with other applications. These include Zendesk, Datadog, New Relic, and Grafana.

There is a Free plan of Better Uptime, which launches tests against ten targets every three minutes. This plan includes notification by email. There are three paid plans, called Freelancer, Small Team, and Business. The tests in all of these plans are launched every 30 seconds. The Freelancer edition includes testing of 50 targets, Small Team has a limit of 100 targets, and the Business plan has no limit on the number of targets that can be nominated for testing. All plans include a 60-day money-back guarantee.

Key features:

  • Five test locations
  • Free plan available
  • 60-day money-back guarantee

Better Uptime Access Free Starter Plan

5. SolarWinds Network Performance Monitor (FREE TRIAL)

SolarWinds Network Performance Monitor image

Although it doesn’t cover websites, SolarWinds Network Performance Monitor is an excellent tool for uptime monitoring on network devices. With this tool, you can view whether devices are classified as Up, Critical, Warning, or Undefined. SolarWinds Network Performance Monitor uses SNMP polling to verify the status of devices throughout your network.

However, you aren’t limited to managing your network through the dashboard display alone. You can also view a network topology map that shows the status of your devices from a geographical perspective. This is referred to as NetPath critical path visualization. NetPath is most useful in live environments where you want to develop a quick perspective of how many devices are up in both your legacy and virtual environments.

All of the status information you see is kept up-to-date by an autodiscovery feature. The autodiscovery feature scans for new devices on startup and adds them to the software automatically. Throughout the lifetime of the product, autodiscovery ensures that new devices are added to your monitoring environment. This is great because you don’t have to do anything extra to monitor it.

Overall, SolarWinds Network Performance Monitor uses SNMP polling to autodiscover and monitor the network devices and connections. The dashboard gives you a commanding view of the network and helps you identify network issues before they become critical.

SolarWinds Network Performance Monitor offers a scalable pricing structure that increases in price the more elements you want. This starts with NPM SL100 which allows you to monitor 100 elements for $2,955 (£2,265). The next version is NPM SL250 which supports up to 250 elements for $6,720 (£5,150). NPM SL500 supports 500 elements for $10,445 (£8,006). The next two versions are NPM SL2000 and NPM SLX. NPM SL2000 is available for $19,345 (£14,827) and supports 2000 elements whereas

NPM SLX supports unlimited elements for $32,525 (£24,930). You can also download a 30-day fully functional free trial.

Key Features:

  • Network uptime monitoring
  • Automated status checks
  • Alerting mechanism

SolarWinds Network Performance Monitor Download 30-day FREE Trial

6. SolarWinds Engineer’s Toolset (FREE TRIAL)

SolarWInds Engineers Toolset Image

SolarWinds Engineer’s Toolset doesn’t include website monitoring but it does offer you the ability to monitor your network in real-time, which will help you isolate possible causes of slow application delivery or downtime on a self-hosted site. These include a Response Time Monitor, Memory Monitor, CPU MonitorInterface Monitor, and TraceRoute. Each of these tools is exceptionally useful for checking up on your network periodically.

With the Response Time Monitor you can view the availability and latency of multiple devices. Response Time Monitor from SolarWinds Engineer’s Toolset provides critical information like the name of the device, IP address, response time, and availability. You can even choose how often to poll the selected devices.

SolarWinds Engineer’s Toolset also has a range of network discovery tools included in the software. There is a Port Scanner, Switch Port MapperIP NetworkBrowser, Ping Sweep, SNMP Sweep, and MAC Address Discovery utility. These help to automatically discover devices throughout the network and keep your manual monitoring down to a minimum.

Overall, SolarWinds Engineer’s Toolset is a great alternative to SolarWinds Network Performance Monitor. While SolarWinds Network Performance Monitor offers a little more depth, SolarWinds Engineer’s Toolset has a high standard of core monitoring capabilities and can be purchased for a lower price of $1,495 (£1,145). You can also get a 14-day free trial download.

Key Features:

  • Status checks for networks
  • Device response times
  • TraceRoute utility

SolarWinds Engineer’s Toolset Download 14-day FREE Trial

7. Site24x7 Website Performance Monitoring (FREE TRIAL)

Site24x7 Website Monitoring

Site24x7 covers all the IT support of websites, enabling it to help web entrepreneurs to keep their sites available. The cloud service performs continual checks on the sites of customers from 90 locations around the world. These checks not only spot when sites go down but also when sites are not deliverable all over the world. That regional outage might be due to the actions of national governments or problems with internet performance.

Websites stand at the top of a stack of services and the failure of one supporting layer will cause the website to go down. So, knowing that a site has gone down is not enough; website owners need to quickly identify why it went down. Site24x7 assists system administrators to prevent outages by identifying equipment and applications that are under pressure.

The ability to spot status issues on the network, server, and in-application performance gives systems administrators a chance to reallocate resources to head off disaster. Should there be no warning signs of an impending outage, the Site24x7 check can identify which internet service caused the failure. These checks include a Domain Expiry Monitor, SSL/TLS Certificate Monitor, a Ping Monitor, and a Web Transaction Monitor, among other automated monitoring tools.

Site24x7 is a cloud-based service provider and is charged for by subscription. The service is available for free to small businesses that only need to monitor up to five websites or servers. Enterprises that need more advanced monitoring capacity than that can choose between four paid editions. Anyone of the paid versions of Site24/7 can be experienced on a 30-day free trial.

Key Features:

  • Uptime tests from 90 locations
  • Root cause analysis
  • Status alerts

Site24x7 Website Performance Monitoring Start 30-day FREE Trial

8. Paessler PRTG (FREE TRIAL)

Paessler PRTG Webite Monitoring with Sensor HTTP

Paessler PRTG is a collection of network, server, and application monitors. This combination is ideal for monitoring the uptime of systems such as websites. Among the long list of monitors, which are called “sensors,” are the HTTP Sensor, the HTTP Transaction Sensor, and the HTTP Full Web Page Sensor.

The HTTP Sensor is the most straightforward of these monitoring services. It checks that a site is available, so this is the basic uptime monitor of PRTG. The HTTP Transaction Sensor digs a little deeper. It is a web services tester that simulates a typical journey of a user through a website. This enables an administrator to check that all elements, such as drop-down lists and shopping carts are working correctly. The HTTP Full Web Page Sensor checks the load times of different elements in a web site by running checks through a browser.

You don’t have to manually monitor these sensors to stay in the loop either. PRTG sends you notifications by email and SMS once a parameter has been exceeded. These alerts are configurable and you can set the trigger conditions that need to be met before a notification is sent to you.

The least expensive version of PRTG is the freeware version which allows you to monitor up to 100 sensors without charge. Any larger enterprises will need to purchase PRTG 500 for $1,600 (£1,226). PRTG 1000 and PRTG 2500 can be purchased for $2,850 (£2,183) and $5,950 (£4,559) for 1000 and 2500 sensors. There are several other versions up to PRTG XL1 which supports unlimited sensors for $14,500 (£11,111). You can download a 30-day free trial.

Key Features:

  • Page speed tests
  • Downtime alerts
  • Transaction monitoring

Paessler PRTG Download 30-day FREE Trial

9. Server Density

Server Density image

StackPath Server Density is a high-profile infrastructure monitoring solution used to ensure the uptime of cloud services, servers, and websites. Subscribers to the cloud-based monitoring system also get the StackPath Website Monitoring service for free. This launches tests on websites from up to 37 locations around the world. The tests launched by the monitor provide a constant record of uptime while also measuring the site’s load times.

This tool has an alerts system that is designed to minimize unnecessary alerts. You can implement wait options to make sure that there is a real problem before an alert is triggered. This helps to prevent freak fluctuations from triggering alerts. There is also an API where you can create your own alert configurations if you require even more control.

One of the things that makes Server Density such an accessible product is that it’s competitively priced. Server Density is available from a price of $10 (£7.66) per month for one server. This increases to $50 (£38)  for five servers and $100 (£76) for 10 servers. The top public price point is $250 (£191) per month for 25 servers. If you require more server uptime monitoring then you’ll need to contact the company directly for a quote.

Key Features:

  • System monitoring
  • Web performance tests included
  • Tests from 37 locations

10. Nagios XI

Nagios XI screenshot

Nagios XI is a network monitoring platform that’s powered by the famous Nagios Core 4 monitoring engine. Nagios XI is one of the most compelling network monitoring tools on CentOS and Redhat Enterprise Linux. This tool provides a centralized perspective of your network and allows you to view whether a service is up or down. This can be seen most clearly in the Host Status Summary or Service Status Summary views where services are categorized and color-coded as Up, Down, Unreachable, and Pending.

Among the many options available to customize the monitoring system, you will find three adaptation wizards that specifically address website monitoring. The Website Wizard gives statuses on a website, which includes its uptime and response times. The Website URL Wizard adds content load times to those details. The Web Transactions Wizard monitors interactive elements in a site and their activation.

However, this software is as much focused on helping you to prevent downtime as anything else. The sheer variety of visual displays allows you to keep tabs on your network health before devices go down. For example, there is a Top Alert Producers Last 24 hours view that shows you those devices that are flaring up with problematic activity.

One of the features that has made Nagios XI gain so much traction is its usage of add-ons. There are tons of different add-ons that you can use to expand the basic functionality of Nagios XI according to your needs. These add-ons are developed by the community giving you a range of options as far as customizing your monitoring architecture.

Nagios XI is also the perfect entry-level tool with a free licensed version, although this is limited to seven hosts. If you require more hosts then you can buy the Standard Edition or Enterprise Edition. The Standard Edition can be purchased for $1,995 (£1,528) with custom dashboards, reporting, notifications, and configuration wizards. The Enterprise Edition can be purchased for $3,495 (£2,677) with scheduled reports. You can download the 60-day free trial of Nagios XI.

Key Features:

  • Website monitoring plugins
  • Page speed reporting
  • Transaction monitoring

11. ManageEngine OpManager

ManageEngine OpManager URL Monitors

ManageEngine OpManager is a network monitoring software tool that provides one of the most complete SNMP monitoring experiences to date. This tool offers users an SNMP monitoring experience that is kept up-to-date through the use of automatic network discovery. In fact, you can use autodiscovery to register up to 15,000 interfaces a minute.

The monitoring service includes a number of live checks on website performance. These are called URL Monitors and uptime is the primary metric provided by this section of OpManager. The monitor measures response times and load times of all elements in a site. The system also checks that the content of the site hasn’t been changed. OpManager gives status reports per server rather than per URL, which is great for spotting problems in a server farm component.

ManageEngine OpManager is available on Linux, Debian, Fedora, Mandrake, and Windows 2012 R2, 2012, 2008 R2, 20082003 Server, Vista, 7, and 2000 Professional SP4. The Essential edition of ManageEngine OpManager can be purchased for $595 (£455) for up to 25 devices. The next version is OpManager Plus which can be purchased for $995 (£762) for 25 devices as well. The largest version is the Enterprise edition which can be purchased for $16,495 (£12,638)  for 500 devices. There is also a free trial.

Key Features:

  • Web app load error reporting
  • Page speed statistics
  • Alerts system

12. Zabbix

Zabbix screenshot

Zabbix is an open-source network, server, and application monitoring too that is ideal for watching your service uptime status. With Zabbix you can view when a service is in a warning or critical state, and when it is down completely. The interesting thing about Zabbix is the depth of its performance monitoring capabilities. You can monitor device temperature, power supply, disk space, and fan status. This provides you with a range of information that can help you to prevent a device from failing.

Zabbix website uptime monitoring and any other web metric gathering, is set up through creating a “web scenario.” A scenario is a series of HTTP requests, which are called “steps.” The monitoring tool then periodically sends these requests to the host of the website and records responses. The user decides the cycle period of these requests.

Zabbix also uses a system of templates for monitoring services. Each template specifies a specific type of resource to monitor. A web scenario can be included in a template. This enables the same tests to be issued on several servers, more or less simultaneously. This tactic is ideal for those who have sites hosted on content delivery networks with cache servers in several different locations.

Each test’s results are logged and it is possible to specify alert notifications under certain conditions.

Zabbix has all the features of a premium-priced application without the hefty price tag. Zabbix can be downloaded for free on CentOS, Debian, Oracle LinuxRed Hat Enterprise Linux, and Ubuntu. Zabbix is available for download.

13. ITRS Synthetic Monitoring

ITRS Group Synthetic Monitoring

ITRS Synthetic Monitoring is a cloud-based service that launches tests on websites from several different geographical locations. As well as offering automated uptime, load time, and response time checks on a site, the service includes transaction testing features that mimic user journeys through the site. As well as websites, this tool can be used to monitor and test applications and APIs under development.

The test locations of ITRS Synthetic Monitoring number 180 and are located in 60 countries. The service offers an alerting mechanism that is based on performance thresholds set by the user. These could be set to warn of deteriorating performance that ties in with a service level agreement.

ITRS Synthetic Monitoring doesn’t have a very sophisticated front end. Instead, the company offers integrations with application performance monitors provided by other companies. These include New Relic, AppDynamics, and Dynatrace.

The alerts issued by ITRS Synthetic Monitoring can be fed through Slack, PagerDuty, or ServiceNow. Another option is to feed performance data through an API into data analysis tools including Splunk and Grafana.

14. Icinga 2

Icinga 2 screenshot

Icinga 2 is a free system monitoring tool that covers networks, servers, and applications. The free tool is actually just the backend of a monitoring system. The group that produces Icinga 2 also offers a browser-based frontend that can be used with Icinga 2 – this is called Icinga Web. There is also a command-line interface for Icinga 2, called icingacli and the interfaces to Incinga 2’s data gathering services can be accessed by developers through a RESTful API.

As an open source system, Icinga 2 is very flexible. However, getting the best out of the monitoring software requires a steep learning curve because you need to become familiar with the system’s coding conventions. The standard reporting screens interface to the analytical engine of Icinga 2 through templates. It is possible to add on screens by locating a template interface command and, if necessary, adapting it.

An example of this process adds on server monitoring through a template that puts uptime service periods on the screen. By editing the Icinga 2 hosts file, that server could be in a remote location. One more piece of code will give you a monitor that focuses on gathering metrics, including uptime reports, on a website. All monitored metrics can have warning thresholds set on them, which generate alerts when tripped.

With the alerts system, you receive notifications by email and text message if any of your systems go down. You also have the option to configure alerts via user or group so that certain members of staff receive certain alerts. This is a useful feature because it allows you to respond to threats promptly when they emerge.

Icinga 2 is available on Debian, Windows, Red Hat Enterprise Linux, SLES, Ubuntu, Fedora, and OpenSUSE. Icinga 2 can be downloaded for free.

Choosing network uptime monitoring software

That concludes our list of the best uptime monitoring tools and software. If you’re operating on a Windows environment then we highly recommend that you purchase SolarWinds Network Performance Monitor or Server Density. Both of these tools offer a perfect mix of accessibility and in-depth infrastructure monitoring. If you’re on Linux then we recommend you try out Zabbix or Icinga 2 based on their configurability!

Uptime Monitoring Software FAQs

What is the best interval for website monitoring?

The issue of website monitoring testing frequency is a difficult one. Some website owners settle for a check every four hours, while others set the test frequency at 15 seconds. Most testing services increase their price with the requested frequency. So, rapidly repeated tests can end up costing a lot of money. Each test also puts a little load on the host of the website, so a high frequency of tests can impair the performance of the site. As a compromise, aim for a frequency of 5 to 15 minutes. However, if you have a high value site, increase that to a test every minute.

What factors affect the downtime of a website?

The causes of downtime indicate the length of time each outage will last. Four types of system downtime leading to a website becoming unavailable are planned downtime for maintenance, an unexpected system error, a hacker attack or an environmental disaster.

Can I check the uptime of my DNS server?

Yes. Many dedicated uptime monitors include a range of uptime statistics, which includes DNS server availability. 

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