Loops is an email sending platform for SaaS teams. It handles marketing, product lifecycle, and transactional email from one place, from onboarding and activation messages to upgrade prompts, receipts, and win-back campaigns.

Lifecycle workflows - build onboarding, activation, upgrade, and win-back emails with triggers, branching, and audience filters.
Themes and editor - set colors, type, and spacing once so every email inherits the brand, and write with an editor or AI help.
Segments - group contacts by properties and events that stay current as product data changes.
API and SDKs - create contacts and send event-triggered email through an API and an npm package.
Integrations - connect Stripe, Supabase, Clerk, Zapier, PostHog, Webflow, Segment, and others, or import contacts from CSV.
Deliverability safeguards - bounce and spam-complaint suppression, send pacing, retries, and manual sending review.

It is used by SaaS product and growth teams that want lifecycle email tied to product data without running a separate marketing and transactional setup. Plans start free; details are on the pricing page.