Guides

Single file

Use the --html flag to deploy any standalone HTML file.

Directory with index.html

If your directory contains an index.html, Leash auto-detects it as a static site.

Example app

from flask import Flask, jsonify

app = Flask(__name__)

@app.route("/")
def index():
    return "<h1>Hello from Leash!</h1>"

@app.route("/api/health")
def health():
    return jsonify({"status": "ok"})

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8080)

Dependencies

flask
gunicorn

Deploy

Example app

const express = require('express')
const app = express()
const port = process.env.PORT || 8080

app.use(express.json())

app.get('/', (req, res) => {
  res.json({ message: 'Hello from Leash!' })
})

app.get('/api/health', (req, res) => {
  res.json({ status: 'ok', uptime: process.uptime() })
})

app.listen(port, () => {
  console.log(`Server running on port ${port}`)
})

package.json

{
  "name": "my-express-app",
  "version": "1.0.0",
  "scripts": {
    "start": "node index.js"
  },
  "dependencies": {
    "express": "^4.18.0"
  }
}

Deploy

Example app

package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
)

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Hello from Leash!")
	})

	http.HandleFunc("/api/health", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
	})

	fmt.Printf("Server running on port %s\n", port)
	http.ListenAndServe(":"+port, nil)
}

go.mod

module my-go-service

go 1.22

Deploy

How it works

Available providers

Connect flow

Or connect from the CLI:

Automatic Detection

The CLI detects database dependencies in your package.json, requirements.txt, go.mod, etc. If it finds PostgreSQL packages (pg, prisma, psycopg, pgx, etc.), it offers to provision a database.

How It Works

• Each app gets its own isolated PostgreSQL database and user
• DATABASE_URL is automatically injected as an environment variable
• Your ORM (Prisma, SQLAlchemy, etc.) creates tables on first connection
• Daily automated backups with 7-day retention

Limits

Bring Your Own Database

If you prefer to use your own database (Supabase, Neon, MongoDB Atlas, etc.), choose option [2] during deploy or set the URL manually:

For MongoDB, use MONGODB_URI. For Redis, use REDIS_URL.

Set a variable via CLI

The CLI prompts you to redeploy immediately so the new value takes effect.

List variables

Delete a variable

Dashboard management

You can also manage environment variables from the dashboard. Navigate to your app, click Settings, and scroll to the Environment Variables section. The dashboard provides a Save & Redeploy button that applies changes and triggers a fresh deploy in one step.

Set visibility during deploy

Change visibility later

Open your app in the Dashboard, go to Settings, and update the visibility level. Changes take effect immediately -- no redeploy required.