Yes. Popular tools like Hotjar, Google Analytics, or any other similar tool asks you to add their own code (tag) to your website to start functioning. When a visitor arrives at your website, the tracking codes are loaded. As a result, these tools start to track the visitor’s actions.
Honestly adding a single tag to your website is not so hard. Simply you can ask the developer, and he/she will do it (sometimes the same day, sometimes may be in a few days, but still reasonable since it only needs to be done once).