Klaviyo API
Klaviyo offers a self-serve REST API at developers.klaviyo.com with calendar versioning across profiles, events, campaigns, flows, catalogs, and reporting. Scoped private keys are created in account settings without approval; OAuth serves marketplace apps.
Frequently asked questions
Klaviyo scores A on the API Report Card. Klaviyo offers a self-serve REST API at developers.klaviyo.com with calendar versioning across profiles, events, campaigns, flows, catalogs, and reporting. Scoped private keys are created in account settings without approval; OAuth serves marketplace apps.
Klaviyo has a workable official integration path. Most engineering teams can build against it directly. Open API: self-serve, documented, with SDKs
Klaviyo is a cloud-based marketing automation and B2C CRM platform that bundles email, SMS, RCS, WhatsApp, mobile push, in-app, and (via the 2025 'Customer Hub' release) helpdesk/service into a single product backed by a unified customer profile and event store.
Vertical: Email & SMS marketing / B2C CRM / ecommerce marketing automation (horizontal SaaS, but heavily indexed on ecommerce). Ecommerce marketers connect their Shopify/BigCommerce/Magento store to Klaviyo, which then ingests every order, product, customer, and behavioral event in near real time.
Klaviyo reports 196,000+ customers across 100+ countries and is the dominant email/SMS platform on Shopify. Industry analysis of 74,777 Shopify Plus stores puts Klaviyo at ~50% adoption at the Plus tier, making it effectively the default.
Yes, for any B2C brand running lifecycle marketing on Klaviyo, it is the system of record for the entire customer engagement and (increasingly) service dataset: every unified customer profile with consent/subscription status, every behavioral event (page views, product views, add-to-cart, custom events) ingested in near real time, every order and product synced from the ecommerce store, every email/SMS/push/RCS/WhatsApp send with full open/click/conversion history, every segment and flow membership transition, predictive analytics outputs (CLV, churn risk, expected next order date), reviews/UGC content, coupon/discount usage, form submissions, and, for Customer Hub users, helpdesk conversations and ticket history.
Founded 2012 in Boston by Andrew Bialecki and Ed Hallen, bootstrapped to profitability before raising $778M across six rounds (Summit Partners led the Series A in 2017; Accel and Shopify participated in later rounds).
Per-account rate limits use a fixed-window algorithm with separate burst (per-second) and steady (per-minute) windows; most endpoints cap at modest values (e.g. Create Webhook is 1/s burst, 15/m steady), forcing complex backoff logic for any high-volume sync. Requests using `additional-fields` or `include` query parameters are subject to stricter rate limits than plain requests, making efficient pagination harder. Full sourced list under Sources below.
Common alternatives include Mailchimp (Intuit), Attentive, HubSpot Marketing Hub, Bloomreach, Salesforce Marketing Cloud, Braze. Graded alternatives appear under "More from the report card" below.
Grades measure one thing: can a customer's engineering team get their own data out programmatically? We check six things (whether a real API exists, how access is gated, data coverage, auth quality, docs and developer experience, and stability) and roll them into a letter grade. Grades get re-verified, and they only move on evidence.