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 a 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:

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