Rendering: JS or Text Only?

Out of the box, does do the "SEO" options crawl using Javascript or Text only? I found that our website redirects to an unsupported page when crawling with JS. Just wondering if the same is happening with SEOTools. Also, if it does use JS, is it using a chrome browser or something else?

No javascript is used, this is why we have the PhantomJs Cloud connector.

Great. Thank you. Can you tell me what browser version is used if one. I’m wondering if the crawler is reaching the unsupported page instead of the intended.