No. Senegal doesn't ask visitors to fill in an online arrival form (also called an entry form, immigration card or landing card) before they travel. Many nationalities visit visa-free for up to 3 months.
Do I still need a visa for Senegal?
An arrival form is not a visa. Whether you need a visa or an electronic travel authorization depends on your nationality, so check Senegal's official immigration website or your own government's travel advice.