How to Secure Your Replit App
Replit makes it easy to build and deploy apps from your browser. However, shared environments, public repls, and AI-generated code create unique security challenges. This guide walks you through securing your Replit application for production use.
Find security issues automatically before attackers do.
Follow These Steps
Use Replit Secrets for all credentials
Never hardcode API keys or passwords in your code. Replit has a built-in Secrets manager that stores environment variables securely. Access them through the Secrets tab in the sidebar.
# In Python
import os
api_key = os.environ.get("OPENAI_API_KEY")
// In Node.js
const apiKey = process.env.OPENAI_API_KEYReplit Secrets are only available at runtime and are not visible in the code editor. They persist across sessions and deployments.
Check that your repl is not accidentally public
Public repls expose your entire source code. If your app contains server-side logic with secrets, make sure the repl is set to private. Go to Settings and check the visibility setting.
Even with a private repl, deployed apps are public by URL. The key is ensuring secrets are in environment variables, not in source code.
Add security headers in your server configuration
Replit apps often lack security headers. Add them in your server framework.
// Express.js
import helmet from 'helmet'
app.use(helmet())
// Or manually
app.use((req, res, next) => {
res.setHeader('X-Content-Type-Options', 'nosniff')
res.setHeader('X-Frame-Options', 'DENY')
res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin')
res.setHeader('Strict-Transport-Security', 'max-age=63072000; includeSubDomains')
next()
})Secure your database connection
If using Replit Database or an external database, ensure connections are encrypted and credentials are stored in Secrets.
// Connecting to external PostgreSQL with SSL
import pg from 'pg'
const pool = new pg.Pool({
connectionString: process.env.DATABASE_URL,
ssl: { rejectUnauthorized: true }
})
// Always use parameterized queries
const result = await pool.query(
'SELECT * FROM users WHERE id = $1',
[userId]
)Implement rate limiting
Replit apps are publicly accessible by URL. Without rate limiting, anyone can hammer your endpoints and exhaust your API quotas.
import rateLimit from 'express-rate-limit'
const limiter = rateLimit({
windowMs: 15 * 60 * 1000, // 15 minutes
max: 100, // limit each IP to 100 requests per window
standardHeaders: true,
legacyHeaders: false
})
app.use('/api/', limiter)Validate all user inputs
Add input validation on every endpoint. Replit AI agent may generate code that trusts user input without checking.
import { z } from 'zod'
const querySchema = z.object({
search: z.string().max(200).trim(),
page: z.coerce.number().int().min(1).default(1),
limit: z.coerce.number().int().min(1).max(100).default(20)
})
app.get('/api/search', (req, res) => {
const result = querySchema.safeParse(req.query)
if (!result.success) return res.status(400).json({ error: 'Invalid parameters' })
// Use result.data
})Configure authentication properly
If your Replit app has user accounts, use a proper auth library. Replit Auth provides a built-in option for simple use cases.
// Using Replit Auth
import { getUserInfo } from '@replit/repl-auth'
app.get('/api/profile', (req, res) => {
const user = getUserInfo(req)
if (!user) return res.status(401).json({ error: 'Not authenticated' })
res.json({ username: user.name, id: user.id })
})Scan your deployed application
After applying security fixes, deploy your Replit app and scan it with VAS to catch any remaining vulnerabilities.
Replit deployments get a .replit.app domain with automatic HTTPS, which is good for transport security.
What You'll Achieve
Your Replit app now uses Secrets for credentials, has security headers, parameterized database queries, rate limiting, input validation, and proper authentication. Your app is hardened for production traffic.
Common Mistakes to Avoid
Mistake
Leaving a repl public when it contains server-side code
Fix
Set repl visibility to private if it contains any server logic. Even better, ensure all secrets are in Replit Secrets so source code exposure does not compromise credentials.
Mistake
Using Replit Database for sensitive data without encryption
Fix
Replit Database is a simple key-value store without built-in encryption. For sensitive data, use an external database with proper encryption and access controls.
Mistake
Not rate limiting public endpoints
Fix
Add express-rate-limit or a similar middleware to all API routes. Without it, attackers can exhaust your API quotas and resources.
Frequently Asked Questions
Are Replit Secrets truly secure?
Replit Secrets are encrypted and only available at runtime. They are not visible in the code editor or to collaborators. However, anyone with execute access to your repl can read them via process.env at runtime.
Can people see my Replit source code?
If your repl is public, yes. Anyone can view and fork your code. Set your repl to private if it contains sensitive logic, and always use Secrets for credentials regardless of visibility setting.
Does Replit provide HTTPS automatically?
Yes. Deployed Replit apps on .replit.app domains get automatic HTTPS. If you use a custom domain, you need to configure SSL through your domain provider or Replit custom domain settings.
How do I handle database security on Replit?
Use an external database like Supabase or PlanetScale with proper access controls. Store the connection string in Replit Secrets, use SSL for connections, and always use parameterized queries.
Ready to Secure Your App?
VAS automatically scans your deployed app for the security issues covered in this guide. Get actionable results in minutes.
Start Security Scan