Instant API – Build type-safe web APIs with JavaScript
Hey there HN! I just wrapped up an all-day documentation spree for Instant API, a JavaScript framework for easily building web APIs that implements type safety at the HTTP interface. It uses a function-as-a-service approach combined with a slightly modified JSDoc spec to automatically enforce parameter and schema validation before HTTP requests make it through to your code. You just write comments above your endpoint functions and voila, enforced type safety contracts between your API endpoints and your developers. OpenAPI specifications are generated automatically as a byproduct of simply…
In plain words
Instant API is a JavaScript framework for building web APIs with automatic type safety at the HTTP interface. It uses a function-as-a-service approach with modified JSDoc comments to enforce parameter validation and schema checking before requests reach endpoint code. The framework automatically generates OpenAPI specifications and handles user input sanitization, eliminating the need for separate schema validation libraries. It is designed for JavaScript developers building web APIs who want to maintain type contracts between endpoints and clients without manual validation work.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hey there HN! I just wrapped up an all-day documentation spree for Instant API, a JavaScript framework for easily building web APIs that implements type safety at the HTTP interface. It uses a function-as-a-service approach combined with a slightly modified JSDoc spec to automatically enforce parameter and schema validation before HTTP requests make it through to your code. You just write comments above your endpoint functions and voila, enforced type safety contracts between your API endpoints and your developers. OpenAPI specifications are generated automatically as a byproduct of simply building your endpoints. This eliminates the need for most schema validation libraries, automates user input sanitization, and prevents your team from developing carpal tunnel syndrome trying to keep your OpenAPI / Swagger specifications up-to-date. We developed it as a side effect of building our own serverless API platform, where it has scaled to handle over 100M requests from users per day. This is an early release, but Instant API has had about six years of consistent development as proprietary software to get to the point it is at today. We have spent the last couple of months modernizing it. We have command line tools that make building, testing, and deploying Instant API to Vercel or AWS a breeze. Additionally, there is a sister package, Instant ORM, that provides a Ruby on Rails-like model management, migration and querying suite for Postgres. Everything you need to build an API from scratch. Finally -- LLMs and chatbots are the the top of the hype cycle right now. We aren't immune, and have developed a number of LLM-integrated tools ourselves. Instant API comes with first-class Server-Sent Event support for building your own assistants and a few other nifty tools that help with AI integrations and chatbot webhook responses, like executing endpoints as background jobs. This has been a huge labor of love -- it has become our "JavaScript on Rails" suite -- and we hope y'all enjoy it!
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