/01 Looking inside a font file
Open a TTF, OTF, WOFF or WOFF2 file and read what is actually in it: the family and style names, version and designer metadata, the licence description, which Unicode ranges it covers, and the OpenType features it ships with.
Useful when you have inherited a font file with an unhelpful name and need to know what it is, what it can do, and whether you are allowed to use it.
/02 Glyph coverage and OpenType features
Coverage tells you whether a font can actually set the languages you need — a face with no Cyrillic or Greek block will silently fall back to something else. Feature tags tell you what typographic controls are available: small caps, oldstyle figures, tabular numerals, ligatures, stylistic sets and alternates.
Knowing the tags matters because you can only switch on a feature the font contains, and many features stay dormant until you ask for them in CSS.
/03 A font viewer that needs no installation
Installing a font just to see what it looks like clutters your system and, for fonts from unfamiliar sources, carries a small risk. This online font viewer opens TTF, OTF, WOFF and WOFF2 files directly in the browser. Drop a file in and you see its preview straight away, with the font never installed or uploaded.
Type your own sample text or use the built-in samples, and check the size waterfall, which shows the same text from small to very large, to judge how the design holds up as body text and as a headline. The font information panel shows the font's name and basic details, and the CSS usage panel gives you an @font-face rule and font-family line ready to paste into a stylesheet.