FontPlop

FontPlop is a free, private font viewer and tester that runs entirely in your browser. Drop in TTF, OTF, WOFF or WOFF2 files to see every glyph, test your own text, and check OpenType features, languages and metrics. Files never leave your device. It also includes a webfont generator, font comparison, a kerning game, and text-style generators. No sign-up required.