The promo applies to domains, hosting, SSL Certificates, Private Email and PremiumDNS.
Promo code for hosting: BDAYHOSTING23
Promo code for domains and other products: BDAYGEN23
Sale ends until October 11, 11:59 PM ET
For detailed instructions, see the Namecheap website:
Update
On this same page, Namecheap lists a different promo expiration date:
