No icon is visible on Firefox 61.0b11 (64-bit), so can't be used. Don't take this review too seriously -- it's probably a bug that I should have filed on GitHub.

....but wait! There it is in the address bar. Works great but you might have mentioned this little peculiarity.

bastante útil para desarrolladores que les gusta investigar tecnologías.

Since last update button was removed. Now wappalyzer displayed in urlbar. Default wappalizer icon not visible. Still good addon but I'm missing the button