Knock

Knock provides product and customer messaging infrastructure that teams use in place of building and maintaining an in-house messaging system. The platform covers transactional messaging, lifecycle marketing, one-time announcements, and in-product messaging, and can deliver across email, SMS, push, chat, and in-app channels from a single system.

The product is organized around three core messaging experiences: workflows, which model multi-step, cross-channel flows using logical function steps (delays, batching, branching, throttling, experiments, fetch and agent steps) while respecting individual user preferences; broadcasts, which are one-time messages initiated from the Knock dashboard and targeted at audiences for announcements, campaigns, maintenance notices, and company updates; and guides, which deliver in-app lifecycle messaging such as paywalls, dialogs, and nudges rendered with a customer's own components and design system. Workflows can be triggered by direct API calls, source events from a CDP such as Segment, one-off or recurring schedules, or audience membership changes, with static audiences populated via API, CSV upload, or reverse ETL and dynamic audiences defined by query rules on user properties.

Supporting capabilities include data ingestion from warehouses, CDPs, reverse ETL tools, and webhooks; dynamic segmentation on attributes, events, and relations; custom object modeling for audiences and templates; hosted and custom preference centers; send windows; multi-tenancy with per-tenant branding, translations, and preferences; internationalization; link and open tracking; analytics; and message debugging. Account-level features cover SAML SSO, directory sync (SCIM), multi-factor authentication, roles and permissions, audit logs, data obfuscation, data retention, and custom domains.

Founding story

Knock was co-founded by Tom Petry and Demetri Themelis, Seattle natives and University of Washington graduates who worked together in finance in New York before returning to Seattle to start a company. Frustrated by the apartment rental and leasing experience, they mapped the renter journey and launched an OpenTable-style booking engine for apartment tours. A third co-founder, Jay Zeng, left in April 2018.

Business model

Knock sells software infrastructure to companies that embed messaging in their products, offering self-serve sign-up alongside sales-assisted motions (demo booking) and an enterprise tier with published plan levels.

Knock offers tiered plans including an enterprise offering; pricing details are not specified in the available material.

Traction

Knock states 99.99% uptime and delivery of hundreds of millions of messages per month, and publishes customer testimonials from engineering and product leaders at Discogs, Vercel, Clay, Amplitude, and Webflow.

Latest developments

Recent product positioning centers on agentic and AI-assisted messaging: building workflows and broadcasts from a single prompt, AI-generated emails in a customer's layout and branding, a Knock agent and agent workflow function, skills, an MCP server, and CLI integration with AI code editors.