WOFF2, the web format
A TTF or OTF font compressed to WOFF2 weighs two to three times less, without touching its outlines: same kerning, same ligatures, same rendering.
Going further: keep only the characters you need
A full font often holds thousands of glyphs (rare accents, Greek or Cyrillic alphabets, symbols). For an English or French website, the “Latin, for the web” option strips out everything unused: often two to five times lighter still.
The code to paste
Each conversion gives you the @font-face rule ready to paste into your stylesheet, with the right weight and style.