Zilla Slab
Google Fonts · Typotheque · 2017

A refined humanist slab serif with robust structure and generous legibility, designed to perform reliably across editorial, branding, and screen contexts.
About
Zilla Slab was developed by Typotheque for Mozilla and embodies the open, accessible character expected of a major technology organisation's brand typeface. Its humanist proportions and open counters keep it friendly and readable across print and digital media alike. The range from Light to Bold makes it a credible workhorse for long-form text, headlines, and interface typography in equal measure.
Classification
A sturdy, humanist slab serif with even stroke weight, open apertures, and a confident structure that balances warmth with professionalism. The slab serifs are square and unbracketed but not mechanical.