[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"glossary-api-first::en":3,"gloss-cluster-api-first::en":20,"gloss-next-api-first::en":9},{"slug":4,"category":5,"name":6,"definition":7,"meta_desc":8,"faq":9,"schema_markup":9,"related":10},"api-first","saas","API-First","API-first is a product and engineering philosophy in which a company designs, documents, and builds its API as the primary interface to the product from the very beginning of development — rather than building a UI first and bolting an API on afterward as a secondary, often incomplete, integration surface. In an API-first product, every capability exposed in the web UI is available through the API too (often the UI itself is simply \"client zero,\" built as one consumer of the same public API everyone else uses), and API design decisions — resource modeling, versioning strategy, authentication scheme, rate limits — are treated as first-class product decisions made early, not an afterthought. This philosophy has become dominant for modern SaaS and dev-tool products (Stripe is the canonical example — its API is the product; the dashboard is a UI wrapped around it) because it unlocks composability: customers and third-party developers can build on top of the product in ways the original team never anticipated, integration partners (Zapier, Make.com) can connect it into broader workflows via webhook + REST\u002FGraphQL, and it forces cleaner internal architecture, since a well-designed public API tends to reflect — and enforce — good internal domain boundaries. API-first products typically invest early in interactive API documentation (via OpenAPI\u002FSwagger specs, tools like Stripe's or Postman's docs, or Mintlify), versioned endpoints (`\u002Fv1\u002F`, `\u002Fv2\u002F`) to avoid breaking existing integrations on change, and predictable, well-scoped authentication (usually OAuth or API keys) from the start. The opposite failure mode — building UI-first and retrofitting an API later — routinely produces an API that's an awkward mirror of internal database tables rather than a clean, intention-revealing interface, and one that inevitably lags behind UI features for years. Concrete worked example: a scheduling SaaS built API-first exposes `POST \u002Fv1\u002Fbookings` as a fully documented, versioned endpoint from launch — accepting `{\"event_type_id\": \"evt_abc\", \"start_time\": \"2026-08-01T14:00:00Z\", \"invitee_email\": \"user@example.com\"}` and returning a booking object with a `webhook`-triggering `booking.created` event. Because the API came first, the company's own web UI, its native mobile app, and a completely unaffiliated third-party developer building a WordPress plugin all call the exact same endpoint — meaning a new feature added to the API instantly becomes available to every one of those surfaces simultaneously, with zero duplicated logic. API-first companies also increasingly treat API rate limits and usage tiers as a monetization lever in their own right, not just a technical safeguard — exposing higher rate limits, webhook concurrency, or additional endpoints as part of paid plan tiers, which turns API design decisions into direct pricing-and-packaging decisions rather than a purely backend engineering concern.","API-first means designing and building a product's API as the primary interface from day one — every feature is API-accessible, with UI as just one client.",null,[11,14,17],{"slug":12,"name":13},"headless-cms","Headless CMS",{"slug":15,"name":16},"oauth","OAuth",{"slug":18,"name":19},"webhook","Webhook",[21,25,29,32,35,38,42,45,48,51,54,57],{"slug":22,"category":5,"name":23,"updated_at":24},"activation","Activation","2026-08-24T02:46:36+00:00",{"slug":26,"category":5,"name":27,"updated_at":28},"aha-moment","Aha Moment","2026-08-24T02:46:37+00:00",{"slug":30,"category":5,"name":31,"updated_at":28},"annual-contract-value","Annual Contract Value (ACV)",{"slug":33,"category":5,"name":34,"updated_at":24},"arpa","Average Revenue Per Account (ARPA)",{"slug":36,"category":5,"name":37,"updated_at":24},"arr","Annual Recurring Revenue (ARR)",{"slug":39,"category":5,"name":40,"updated_at":41},"auto-renewal-clause","Auto-Renewal Clause","2026-08-24T02:46:38+00:00",{"slug":43,"category":5,"name":44,"updated_at":41},"build-vs-buy","Build vs. Buy",{"slug":46,"category":5,"name":47,"updated_at":28},"burn-multiple","Burn Multiple",{"slug":49,"category":5,"name":50,"updated_at":41},"burn-rate","Burn Rate",{"slug":52,"category":5,"name":53,"updated_at":24},"cac","Customer Acquisition Cost (CAC)",{"slug":55,"category":5,"name":56,"updated_at":24},"cdn","Content Delivery Network (CDN)",{"slug":58,"category":5,"name":59,"updated_at":24},"churn","Churn"]