Glossary

Publishing an app involves a bunch of names everyone uses and nobody explains. Here's what each one means in practice. No need to memorize them: come back here whenever a term shows up.

The "other side" of your app: the server where user data, login, and rules live. The app on the phone is the storefront; the backend is the warehouse. In Kasy you choose between Firebase (Google's), Supabase, or your own API.

Deploy

Publishing something to a server. When you run kasy deploy, your backend's functions and rules go up to the cloud and start taking effect. Without deploy, they only exist on your computer.

Cloud Function / Edge Function

A small piece of code that runs on the server, not in the app. It handles tasks the app can't do (storing secrets, validating purchases). Cloud Function is Firebase's name for it; Edge Function is Supabase's. You don't need to write them: the kit already ships them ready, and kasy deploy publishes them.

Webhook

A "let me know when it happens." You give a service (RevenueCat, Stripe) a URL of yours, and it calls that URL on its own when something happens: a purchase, a cancellation. That's how your database finds out someone subscribed, even with the app closed.

Secret

A password or key that can never show up in the app's code (anyone can open an app and read what's inside it). Secrets stay stored on the server. Example: the OpenAI key for AI chat lives in a secret, and the app talks to it through a function of yours.

`.env`

A text file at the root of your project with the keys the app uses (RevenueCat, Sentry, etc.), one per line. It stays out of Git on purpose, so the keys don't leak when you share the code. kasy run reads this file automatically.

OAuth

The standard behind "Sign in with Google/Apple/Facebook." Instead of creating yet another password, the user authorizes the app to use the account they already have.

Authorized origin

On the web, Google only accepts logins coming from addresses you've registered (e.g., https://yourapp.com). If social login fails on the web, it's almost always because the address isn't on the list.

Token

A "digital badge" the app receives when the user logs in and presents on every request to the server. That's how the server knows who is asking without requesting the password every time.

Stores and payments

Sandbox

The stores' pretend environment: you make a purchase with the real Apple/Google modal, but no money gets charged. Used for testing before publishing. One detail: in Sandbox, subscriptions last minutes (a monthly one renews every 5 min); that's normal, not a bug.

Entitlement

The "permission" a purchase unlocks in the app. The user buys the premium_monthly product → gets the premium_access entitlement → the app unlocks the content. RevenueCat is what controls this.

Offering / Paywall

Paywall is the "subscribe to premium" screen. Offering is the set of plans shown on it: you build it in the RevenueCat dashboard, without touching the code.

Trial

A free period before the first charge ("7 days free, then $19.90/month"). Configured in the store, and the kit shows it on the paywall automatically.

Bundle ID / Application ID

Your app's "ID number": a unique identifier shaped like com.yourcompany.yourapp. Apple calls it Bundle ID; Android calls it Application ID. It needs to be the same everywhere (project, App Store Connect, Play Console).

Keystore / Certificate

The "digital signature" that proves the app is yours. Android uses a keystore file; Apple uses certificates. Guard it with your life: whoever loses the keystore can no longer update the app on Play Store.

Build number vs version

Version (1.0.2) is what the user sees in the store. Build (42) is an internal counter that needs to go up on every submission. kasy ios release bumps the build on its own.

Web

DNS

The internet's "phone book": it translates yourapp.com into the server's address. When you point a custom domain at Firebase Hosting or Vercel, you create DNS records at the site where you bought the domain.

PWA

Progressive Web App: your app running in the browser, but installable as if it were native (icon on the home screen, runs full-screen). Kasy's web build already ships as a PWA.

Tools

CLI

Command-Line Interface: a program you use by typing commands in a terminal, instead of clicking through windows. kasy is a CLI.

MCP

A plug that connects your AI (Claude, Cursor) to an external tool. Kasy's main path is the Kasy MCP (kasy-mcp): you paste a JSON snippet into your client and ask "prepare my machine", "create a project", "run the app", or "publish iOS", without typing the CLI. Full page: Kasy MCP. Install: Install Kasy. There are also third-party MCPs, such as RevenueCat and Stripe, for building a subscription catalog from chat.

SDK

A ready-made code package a service provides so the app can talk to it (RevenueCat's SDK, Firebase's...). The kit already installs and configures the SDKs: you only touch them if you want to customize something.

Missing a term? The guides explain concepts in the context where they show up: start with Concepts.

Last updated on 08/02/2026

Infrastructure

Backend