[1][3] The Google Optimize editor was a Chrome extension that allowed changing some aspects of visible HTML elements.
Changes were then applied with JavaScript tailored by rules set in an experiment.
They could also modify HTML inside chosen elements, which allowed adding more advanced changes.
The editor alone would not work for creating complicated tests, especially on pages with dynamic content such as Angular, Vue or React.
To use GO on more complicated, dynamic pages, manual work by programmers was required to integrate experiments into frontend or backend code.