Twilio is a US cloud communications company providing APIs for SMS, voice, video, email and customer data, which developers use to build messaging and contact-centre features.
Klaviyo is a US marketing automation platform focused on email and SMS marketing for e-commerce brands, using customer data from Shopify and other stores to personalise campaigns.
Braze is a US customer engagement platform that helps brands send personalised messages across email, push, in-app and SMS using real-time customer data.