Glossary of Terms

Website Availability

What is Website Availability?

Website availability refers to whether a website is accessible and working properly when a person or customer visits it. Essentially—is the website available, or is it not?

Note: Website availability is often mistaken for “domain availability.” Or, whether a domain name is available for purchase or use. If you’re looking for domain availability, click here.

Website availability is a metric tracked by performance monitoring software. Performance monitoring software tracks the performance of each part of an application so that engineers and I.T. professionals are notified proactively if issues arise.

Website availability is calculated using the uptime metric. Uptime means the amount of time the application or website was live or working properly.

Uptime / total period of operating time = Website Availability


Uptime / total period of time = Website Availability

To calculate availability for the month of December, take the total number of minutes the website was available and divide by 44,640 (total number of minutes in December).

If the website experiences 10 minutes of downtime, the formula would be:

44,630 / 44,640 = 99.97% for the month

Note that some organizations consider latency to be downtime while others just consider downtime to be when the app is unavailable.

Website availability: an uptime example

Uptime is typically a service level objective that must be met by the provider of a service. For example, if Salesforce promises 99.999% availability to its users in its service level agreement (SLA), then it must keep its application live 99.999% of the time.

If a service level agreement promises 99.999% availability, you’re looking at a yearly total downtime allowance of about 5 minutes or 6 seconds a week, and not quite 1 second per day. Because website availability is business-critical—meaning the company’s profits depend on it — it’s essential for companies to keep websites live, working, and available to potential customers.

It’s also important to note that availability applies not only to websites, but also to applications and any other component that relies on Internet connectivity.

What makes a website or application available?

Websites are so much more than meets the eye. There’s the page a visitor lands on, but then, there’s a vast web of interconnected parts powering the front-end that visitors see.

What are those parts working behind the scenes?

  • Servers that store all the information on the website.
  • Content Delivery Networks (CDNs) that deliver information to the user’s computer or smartphone.
  • Domain Name System (DNS) which turns a website URL, like, into a numeric address that computers and servers understand.

Each of these working parts is vital to website availability. If one part goes down, then the website can experience an outage or slowdown. When developers create a website, they consider each of these components.

For example, if files are too large, it slows download speeds because that’s more data traveling from the CDN to the user’s computer.

Third-party content and applications

Beside the components of a website listed above, there are often other third-party applications and content on a website that the website owner doesn’t control.

For example:

  • Third-party ad services that display ads to viewers on a site.
  • Social media tags that show social posts in a page or track the performance of certain links.
  • Analytics tools that integrate with a website to track viewer behaviors.

Why is website availability important?

The dot-com bubble brought with it ecommerce—the ability to shop online 24/7. In addition to ecommerce, the dot-com burst also brought about a boom in SaaS applications (Software as a Service) wherein users pay a subscription to have access to software that’s hosted online or in the cloud (like Netflix or Salesforce).

This SaaS and ecommerce shift makes website availability even more essential to businesses as they need to retain customers who are subscribed to their services. Ecommerce businesses need to keep websites live so returning customers and new customers can make purchases.

Let’s review some of the principal reasons why companies need to monitor website availability.

Bottom line

A company’s profit is the most important metric or key performance indicator (KPI) that website availability affects. If a site or application is down, or even too slow, customers can’t shop and SaaS application users may abandon a company for a competitor’s app. For example, latency cost Amazon $1.6 billion in one second.

Customer retention

For SaaS businesses, customer retention is vital to the health of the organization. A study by Bain and Company shows that a 5% increase in retention can equal an increase in profits as high as 95%. Since users pay a subscription fee each month or each year, hanging onto those customers is the primary way SaaS businesses increase profits year over year.

When a website or application is slow or unavailable, companies damage their own reputation, even if the outage or lag isn’t their fault, but is the fault of a vendor’s application. For example, Business A’s website might rely on data from Company B’s application. Company B’s application goes down. Business A’s application also goes down since it was relying on Company B. Business A’s customers are upset about the outage, even though it’s technically Company B’s outage.

Meeting SLAs

SaaS companies have legal agreements with their subscribers or customers. These agreements, called service level agreements (SLAs) outline the level of performance the application or website must meet.

If the promised levels of performance are not met, the SaaS company is in breach of this contract. A breach results in fines paid to the subscriber or customer. It’s important that companies monitor their own availability to meet their SLAs. Also, companies can monitor the availability of their SaaS providers to keep them accountable to their SLAs.

How can companies keep their websites available?

To keep websites and applications available, IT teams must monitor each component of the website or application. IT teams must also have communication plans in place for when outages do occur.

Companies must monitor from multiple endpoints and locations to get an accurate picture of customer experience.

Observe inside and outside the firewall

Companies often have multiple offices and use both internal (inside the firewall) SaaS applications and also provide SaaS to their customers (outside the firewall). They need to observe both internal and external performance.

When internal applications go down, it hurts a company’s productivity, and therefore, profit. External issues cause problems for users, which directly impacts revenue.

Observe from the places customers are coming from

A SaaS or ecommerce company’s users aren’t all in one city or location. The web is global and so are its users. Companies need to observe from different geographic locations to make sure that those various locations aren’t experiencing varying levels of performance.

For example, if performance is measured from both LA and New York, IT teams can pinpoint an issue faster should they detect latency in LA but not in New York.

Observe third parties

Most applications and sites nowadays rely on third-party vendors. For example, a media site might use a third-party app to manage its display ads. The media company cannot control the code of the display ad app, but they can observe the performance of the app to ensure it’s not the cause of performance failure. If it is the cause of failure, they can alert the right people from the display ad app company.

Because there are so many components that make up a modern application or site, it’s important to observe all third-party vendors. Otherwise, a business cannot be sure of the source of any issue as they’re blind to the performance of their third parties.

Observe website availability to identify and resolve issues quickly (MTTI & MTTD)

Companies need performance observation software to help identify and resolve performance issues.

MTTI, or mean time to identify, is how long it takes to identify the source of an issue. If IT professionals observe the performance of each piece of their application, they can quickly identify the source of a problem.

If they aren’t observing each piece of their application or infrastructure, then they cannot be 100% certain that they’ve located the true source of a problem. Those blind spots also leave them susceptible to higher MTTI and longer periods of outage.

MTTR, or mean time to resolve, is how long it takes to resolve an issue once it’s identified. If IT professionals observe all the parts of their website or app,  they can also solve problems faster since they can get to the root cause quicker.


Businesses need to be able to communicate:

  • Internally — It’s important for companies to have an internal communication plan in place so that the appropriate teammates are alerted of issues they’re responsible for.
  • Externally — it’s equally important for companies to know who is responsible for alerting third parties when the third party is responsible for the outage.

What affects website availability?

There are a number of things that can affect website availability. For example:

  • Attacks - Web attacks are a bigger threat than ever. Hackers can take down servers, manipulate DNS functions, and more. Learn more about web security and observability here.
  • Performance issues - Performance issues can range from slow download speeds to a full-on outage. Any component in a website or app’s infrastructure can cause an outage or slowdown.
  • Changes and fixes - Companies continually update their websites and apps with both bug fixes and improved features. These fixes and other changes can create performance issues if thorough tests aren’t run before their release.

To know what needs to be resolved and to identify the source of an issue (be it hacker, performance, or a recent fix) a business needs to observe each component contributing to their website or application: the front-end, the back-end, and all the third parties that work together to create the website or application.


Website availability depends on many moving parts. What a website or applications visitor sees is merely a small portion of the entire working mechanism.

Each piece or component must be observed to sustain and improve website availability. A company’s profit, it’s customer experience, and its own legal agreements are all on the line without a reliable, available website or application.