Doppler is an email marketing and transactional email service.
Facebook pixel is an analytics tool that allows you to measure the effectiveness of your advertising.
Google Tag Manager is a tag management system (TMS) that allows you to quickly and easily update measurement codes and related code fragments collectively known as tags on your website or mobile app.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Stripe offers online payment processing for internet businesses as well as fraud prevention, invoicing and subscription management.
Vercel is a cloud platform for static frontends and serverless functions.