The site template is a complex of graphic files, blocks HTML and Css codes as well as various scripts, responsible for the visual presentation of the web resource. In other words, this is his frame with design elements.

Typically, most modern Cms (engines) sites support the ability to change templates (those) “on the fly”, i.e. a design replacement that takes only a few seconds does not affect the availability of visitors and does not affect its information content.

When promoting search engines, the site template itself does not play a fundamental role. But his choice can have an indirect effect. 

So, for example, installing too bulky, heavy a template on the site will make its pages load for a long time and this will undoubtedly make many visitors nervous, especially those who came in for the first time. As a result, many of them will leave without waiting for the full loading of the pages, which will be counted by search engines as “refusal", worsening the statistics of behavioral indicators. 

Impression of visitors from the visual display of the site and the convenience of using it (usability) also largely depends on the selected template and indirectly, through all the same behavioral factors, affects his progress in search engines.