Instagram primarily uses the Instagram Sans font, which comes in light, regular, medium, and bold typefaces. This custom font was designed to reflect the shape of the glyph and Instagrams commitment to simplicity and craft. The font is a contemporary remix of grotesque and geometric styles, designed with accessibility and global scripts in mind.

However, Instagram also uses other fonts for different sections of its mobile app. For example, the Aveny-T font is used for the "Modern" font in Type mode, while Cosmopolitan is used for the "Neon" font. The font used for Instagram Stories and Reels depends on the mobile platform. On iOS devices, the San Francisco font is used, while on Android devices, the Roboto font is used.

In summary, Instagram primarily uses the Instagram Sans font, but also uses other fonts for different sections of its mobile app.