Install FLIN

The Cognitive Programming Language Built-in AI

Code that thinks, remembers, and heals itself.

ADetected: macOS[change]

Run this in your terminal:

curl -fsSL https://flin.sh | bash

Download for Windows (64-bit)

Or use PowerShell:

irm https://flin.sh/install.ps1 | iex

Zero Config

One file = full app. No build tools, no dependencies.

Memory Native

Built-in database with time travel. Every entity has complete history.

Cognitive

Self-healing apps that see, reason, and fix themselves.

A Complete Todo App. One File.

No dependencies. No config. No build step.This is real, working FLIN.

app/index.flin
// 1. Define your data (10 types, enums, 49 validators)
enum Priority { Low, Medium, High, Critical }

entity Todo {
    title: text @required @minLength(2)
    done: bool = false
    priority: Priority = "Low"
    due: time

    @index(done, priority)
}

// 2. State
newTitle = ""
filter = "all"

// 3. Functions (always type entity params)
fn add() {
    todo = Todo { title: newTitle }
    save todo
    newTitle = ""
}

fn toggle(t: Todo) {
    t.done = !t.done
    save t
}

fn remove(t: Todo) {
    delete t
}

// 4. Choose what to show
todos = match filter {
    "done" -> Todo.where(done == true)
    "pending" -> Todo.where(done == false)
    _ -> Todo.all
}

// 5. Template (just HTML + {curly braces})
<h1>My Todos ({Todo.count})</h1>

<form submit={add()}>
    <input bind={newTitle} placeholder="What needs doing?" />
    <button type="submit">Add</button>
</form>

{for todo in todos}
    <div>
        <input type="checkbox"
            checked={todo.done}
            change={toggle(todo)} />
        <span>{todo.title}</span>
        <button click={remove(todo)}>x</button>
    </div>
{/for}

enum PriorityType-safe enums — auto-validated on save

L3-9

Entity = Database Table10 types, 49 validators, enums, @index

L14-15

Variables = Reactive StateChange a variable, UI updates automatically. No useState, no signals, no stores.

L18-21

save = Persist to DatabaseOne keyword. Data survives restarts. That's it.

L32-36

match = Pattern MatchingQuery your database with readable expressions. Chain .where(), .order_by(), .limit().

L39

{Todo.count} = Live QueriesDatabase queries work directly in templates. Always up to date.

Already Know TypeScript?

FLIN accepts JS/TS syntax as aliases.Use what you know. Learn the rest gradually.

These JS/TS habits work in FLIN

string=text

boolean=bool

number=float

null=none

function=fn

console.log(x)=log(x)

name.length=len(name)

TypeScript-style FLIN code
// Write TypeScript-style types
entity User {
    name: string
    email: string
    age: number
    active: boolean = true
}

// Use the function keyword
function greet(user: User) {
    console.log("Hello, " + user.name)
    return user.name.length
}

// null works like none
function findUser(id: int) {
    result = User.find(id)
    if result == null {
        return null
    }
    return result
}

Only 3 things are different

{ key: "val" }["key": "val"]Maps use square brackets

import X from YNot neededAuto-discovered by file location

class User {}entity User {}Built-in persistence + database

That's it. Everything else from JS/TS works unchanged: let, const, ??, ++, +=, try/catch, async/await.

Start with a Template

Choose your starting point. From minimal to fullstack.

Minimal1 file

flin new myapp

Quick experiments, learning syntax

StarterBeginner

flin new myapp --template starter

Counter demo, reactive variables

TodoIntermediate

flin new myapp --template todo

Entities, validators, CRUD operations

FullstackAdvanced

flin new myapp --template fullstack

Auth, API routes, dashboard, i18n

FlinUI180 components

flin new myapp --template flinui

Full component library with live demos

E-commerceAdvanced

flin new myapp --template ecommerce

Products, cart, checkout, orders, admin dashboard

Browse more at FLIN Hub

Visit hub.flin.dev for ready-made templates. Copy, don't install - you own the code. hub.flin.dev

What You Get

File-Based Routingapp/about.flin - /about

Built-in Databaseentity User - No SQL needed

Time Traveluser.history - See all past versions

180 UI ComponentsFlinUI embedded in the binary

Zero ImportsComponents auto-discovered

Guards and Middlewareauth: required, rate_limit: 5/min

AI Gatewayask.claude - Built-in AI

380+ Built-in FunctionsStrings, math, crypto, dates — no packages

180 Built-in UI Components

FlinUI ships inside the FLIN binary. No npm install, no CDN, no config.Just use PascalCase names and they work.

Forms & Input

Input, Select, Checkbox, Switch, DatePicker, TagsInput, MultiSelect, RichTextEditor, CodeEditor

30 components

Data Display

Card, Badge, Avatar, Table, DataTable, Progress, Timeline, Calendar, Carousel, Accordion

31 components

Charts

BarChart, LineChart, PieChart, AreaChart, RadarChart, ScatterChart, HeatmapChart, GanttChart

13 components

Navigation

Navbar, Sidebar, Tabs, Breadcrumb, Pagination, Menu, ContextMenu, Dropdown, BottomNav

13 components

Layout

Grid, Flex, Stack, Container, Row, Divider, Section, Hero, ResizablePanels, ScrollArea

17 components

Templates

LoginForm, DashboardLayout, PricingTable, EmailClient, BlogLayout, FileManager, AuthLayout

14 components

E-commerce

ProductCard, CartItem, CartSummary, CheckoutForm, OrderSummary, ProductGallery, CouponCode

8 components

AI / Chat

ChatBubble, ChatInput, ChatMessages, AIResponseCard, AIPromptInput, AILoadingState

6 components

app/dashboard.flin
// No imports needed - just use them

<Navbar>My App</Navbar>

<Grid columns="3">
    <StatCard label="Users" value="1,234" icon="users" />
    <StatCard label="Revenue" value="$12K" icon="trending-up" />
    <StatCard label="Orders" value="89" icon="shopping-cart" />
</Grid>

<Card>
    <BarChart data="45,72,38,91,65" labels="Mon,Tue,Wed,Thu,Fri" />
</Card>

<Icon name="check" size="24" color="green" />
// 1,667 Lucide icons embedded

Zero ImportsComponents are compiled into the binary. No node_modules. No package.json.

1,667 IconsFull Lucide icon set. Use Icon component with any name, anywhere.

Dark ModeEvery component supports light and dark themes via CSS variables.

Server RenderedPure HTML + CSS output. No JavaScript bundle. Fast on any device.

Browse all 180 components with live demos:

flin dev embedded/flinui

Use FLIN as a Standalone Backend

Already have a React Native, Flutter, or Next.js app? Use FLIN as your backend.No Node.js. No separate database. Just FLIN.

Full-Stack Recommended

FLIN handles frontend + backend + database

FLIN = React + Node.js + PostgreSQL

Backend Only

Use with React Native, Flutter, Next.js

FLIN = Node.js + PostgreSQL

Database Layer

Auto-generated REST API for your data

FLIN = PostgreSQL + Supabase

JWT

JWT Authenticationjwt_create(), jwt_verify(), Bearer tokens

KEY

API Keysapi_key_generate(), guard api_key

Rate Limitingguard rate_limit(100, 60)

2FA

Two-Factor AuthTOTP, QR codes, backup codes

OAuth2Google, GitHub, Discord, Apple

WebSocketsReal-time, rooms, broadcast

Learn More

Fullstack Template Structure

Everything you need. Zero configuration.

flin new myapp --template fullstack
myapp/
├── .flindb/                    # Database (auto-created on first save)
│   ├── wal.log                 # Write-Ahead Log (CRC-32 checksums)
│   ├── lock                    # Process lock (prevents dual access)
│   ├── data/
│   │   ├── Todo.flindb         # All Todo records (per entity type)
│   │   ├── User.flindb         # All User records
│   │   └── ...                 # Auto-checkpointed from WAL
│   ├── schema.flindb           # Full entity schemas (self-describing)
│   ├── meta.json               # Database metadata
│   ├── blobs/                  # File storage (content-addressable)
│   └── semantic/               # Embeddings for semantic search
│
├── app/                        # File-based routing
│   ├── _middleware.flin        # ROOT MIDDLEWARE (global auth)
│   ├── index.flin              # Home → / (public)
│   ├── login.flin              # Login → /login (public)
│   ├── register.flin           # Register → /register (public)
│   │
│   ├── dashboard/              # Protected dashboard area
│   │   ├── _middleware.flin    # DASHBOARD MIDDLEWARE
│   │   ├── index.flin          # Dashboard → /dashboard
│   │   ├── profile.flin        # Profile → /dashboard/profile
│   │   └── settings.flin       # Settings → /dashboard/settings
│   │
│   └── api/                    # API routes
│       ├── _middleware.flin    # API MIDDLEWARE (CORS, rate limits)
│       ├── auth.flin           # /api/auth (login/logout)
│       ├── users.flin          # /api/users (GET, POST)
│       └── users/
│           └── [id].flin       # /api/users/:id (GET, DELETE)
│
├── components/                 # Reusable components (auto-discovered)
│   ├── Header.flin             # <Header />
│   ├── Footer.flin             # <Footer />
│   ├── Navbar.flin             # <Navbar />
│   └── Card.flin               # <Card />
│
├── layouts/                    # Page wrappers (auto-discovered)
│   └── default.flin            # Default layout with {children}
│
├── lib/                        # Shared functions (auto-discovered)
│   ├── utils.flin              # Utility functions
│   ├── validators.flin         # Validation functions
│   ├── formatters.flin         # Formatting functions
│   └── constants.flin          # App constants
│
├── entities/                   # Data models
│   └── User.flin               # User entity
│
├── styles/                     # Shared CSS (auto-injected)
│   ├── global.css              # Base styles, reset
│   ├── theme.css               # Light/dark theme tokens
│   └── components.css          # Shared component styles
│
├── i18n/                       # Internationalization
│   ├── en.flin                 # English
│   ├── fr.flin                 # French
│   └── es.flin                 # Spanish
│
├── public/                     # Static assets
│   ├── favicon.ico
│   ├── icon.png
│   └── logo.png
│
├── backups/                    # Database backups
│
├── .env                        # Environment variables (secrets)
├── .gitignore                  # Ignores .flindb, .env, backups
├── llms.txt                    # LLM instructions
├── flin.config                 # Project configuration
└── README.md

Fapp/ = routes

D.flindb/ = database

Ccomponents/ = auto-discovered

After installation:

Terminal
# Create your first app
$ flin new my-app
$ cd my-app

# Start development server
$ flin dev

# Open http://localhost:3000

Your Entire Toolchain

One binary replaces Node.js, npm, webpack, prettier, jest, and more.No dependencies. No plugins. No config files.

flin --help
# Create
flin new myapp      [--template starter|todo|fullstack|flinui]
flin new myapp      [--demo]  — alias for --template fullstack

# Develop
flin dev            [path] [--port 3000] [--verbose]
flin run            file.flinc — Run compiled bytecode

# Quality
flin check          app.flin — Type check without building
flin fmt            [file.flin] [--check]
flin test           [--filter "pattern"] [--verbose]

# Production
flin build          app.flin [--output dist/]
flin start          [path] [--port 3000]
flin deploy         (coming Q2 2026)

# AI / Semantic Search
flin dev            — AI enabled by default (fastembed)
flin dev --lite     — No AI, minimal footprint (embedded/IoT)

# Manage
flin update
flin gc             [--dry-run|--sweep] [--grace-period 3600]
flin self uninstall

flin docs
# Syntax reference
flin docs syntax              All syntax topics
flin docs syntax variables    Detailed topic
    Topics: variables, entities, types, collections,
    operators, expressions, control, views, events

# Examples
flin docs examples            List all examples
flin docs examples todo       Show specific example

# Function reference (380+ functions)
flin docs len                  Help for a function
flin docs functions            All functions by category
flin docs functions strings    Functions in category
flin docs search "date"        Search functions

Learn FLIN by Example

4 built-in apps included with FLIN. Run them instantly to master the language.Everything is included -- no extra downloads.

Level 1Beginner

Starter

Reactive counter in ~10 lines. Learn variables and events.

Reactive variablesEvent handlersInline styles

flin dev embedded/starter

Level 2Intermediate

Todo App

Classic TodoMVC. Learn entities and data persistence.

Entity definitionsCRUD operationsValidatorsQueries

flin dev embedded/todo-app

Level 3Advanced

Fullstack App

Complete app with auth, API, uploads, WebSocket, 2FA, OAuth.

OAuth (Google/GitHub)2FA/TOTPWhatsApp OTPFile uploadsWebSocketGuardsi18n

flin dev embedded/fullstack

Level 4Component Library

FlinUI Showcase

Browse all 180 components with live demos and dark mode.

180 components1,667 iconsChartsTemplatesE-commerceAI/ChatDark mode

flin dev embedded/flinui

Pro tip: The fullstack app demonstrates every FLIN feature. Copy code from it to your own projects. You own everything -- no node_modules, no dependencies.

Manage Your Installation

Configuring PATH

FLIN installs to ~/.flin/bin on Unix or %USERPROFILE%/.flin/bin on Windows.

The installer automatically adds this to your PATH. If flin --version doesn't work after install, restart your terminal or run:

source ~/.flin/env

Updating FLIN

Update to the latest version:

flin update

Or re-run the install script to get the latest version.

Uninstalling FLIN

To completely remove FLIN from your system:

flin self uninstall

This removes the binary and cleans up PATH entries.