Uptime in IT is when a piece of equipment (such as a computer or other device) is functioning or able to function. Uptime is a measure of system reliability, expressed as the percentage of time when a computer has been working and available. Uptime is the opposite of downtime.

This measure is often checked and controlled by uptime monitoring, the process of testing and verifying that end-users can interact with a computer, device, internet website or web application as expected. 

Website uptime (as opposed to website downtime) is when a website is available online or functions well enough for end-users to complete the main task. 

Website uptime means that the end-user can:

  • access the website,
  • perform and complete the main task on the website.

For example, the main task in e-commerce is to add to basket and buy products or services. Another example from the accommodation/hotel industry is that users can choose and book a room.

Nowadays, uptime is more complex than we believed even a few years ago. Currently, access to a website is not the only factor defining uptime. 

We can easily imagine a situation where an e-commerce website responds with the 200 status HTTP code, but is down. The most simple example of such a website will be a blank page without content, or broken content but still returning 200 HTTP status.

Advanced website uptime monitors can check many different checkpoints and functionalities like:

  1. Advanced Availability Monitoring
    1. Verify TLS/SSL certificates for expiration and content,
    2. Check on DNS health by verifying critical fields on a DNS entry,
    3. Communicate with POP3, SMTP, and IMAP email servers,
    4. Query and check MySQL and SQL Server databases, and
    5. Check availability and downloads for FTP and SFTP.
  2. Performance and function monitoring
  3. Web Performance monitoring
  4. Web Application Monitoring
  5. API Monitoring