Deploy and Host Selenium with Flask on Railway

What is Selenium with Flask?

Selenium with Flask is a lightweight browser automation stack for Railway. This template runs as two connected services: a Flask REST API service and a Selenium Standalone Chrome service.

The Flask service exposes HTTP endpoints that trigger browser automation tasks, while the Selenium service runs the remote Chrome browser environment. Communication between both services uses Selenium Remote WebDriver, making the setup cleaner, more scalable, and easier to maintain than bundling Chrome, ChromeDriver, and the API server into a single container.

About Hosting Selenium with Flask

Hosting Selenium with Flask on Railway gives you a ready-to-use setup for building browser automation APIs, scraping workers, and internal automation tools.

This template separates the application layer and browser automation layer into two services:

Flask REST API Handles incoming HTTP requests, API routes, scraping logic, and response formatting.
Selenium Standalone Chrome Runs headless Chrome and exposes a Remote WebDriver endpoint for browser sessions.

Instead of installing ChromeDriver directly inside the Flask container, the Flask app connects to the Selenium service through a remote URL. When both services run inside Railway, you can use Railway private networking for internal service-to-service communication.

Example internal Remote WebDriver URL:

http://standalone-chrome.railway.internal:4444/wd/hub

If you access Selenium from outside Railway, use the public Selenium service URL instead.

Example public Remote WebDriver URL:

https://your-selenium-service.up.railway.app/wd/hub

This architecture keeps the Flask API lightweight while allowing Selenium to run as a dedicated browser automation service.

How to Use

After deploying this template, Railway will create two services:

Flask REST API
Selenium Standalone Chrome

Open the generated Railway domain for the Flask service to test the starter API.

The Flask service connects to Selenium using a Remote WebDriver URL. In a Railway-to-Railway setup, use the private internal Railway URL for faster and private service communication.

Example environment variable for the Flask service:

SELENIUM_REMOTE_URL=http://standalone-chrome.railway.internal:4444/wd/hub

If you run the Flask app locally on your computer, you cannot use the .railway.internal URL. Use the public Selenium Railway URL instead:

SELENIUM_REMOTE_URL=https://your-selenium-service.up.railway.app/wd/hub

Test the Scrape Endpoint

This template already includes a sample scrape endpoint in the Flask REST API service.

After deployment, test the Flask service using:

https://your-flask-service.up.railway.app/scrape

You can also test it with curl:

curl https://your-flask-service.up.railway.app/scrape

If the Flask service can connect to the Selenium Standalone Chrome service correctly, the endpoint should return a JSON response from the sample scraping task.

How to Check Selenium Status

You can verify the Selenium service by opening its status endpoint.

Private Railway network:

http://standalone-chrome.railway.internal:4444/status

Public Railway URL:

https://your-selenium-service.up.railway.app/status

If the Selenium service is running correctly, it should return a JSON response showing the Selenium node status.

Customization

If you want to customize the source code, use one of the workflows below.

Via Railway CLI

Use this workflow if you want to edit the project locally and redeploy changes directly from your machine using Railway CLI.

Deploy the template.
Clone the repository from Source Repo or Upstream Repo in the Railway dashboard.
Enter the project directory:

cd your-project-directory

Link your local project directory to the deployed Railway project:

railway link

Check the linked project, environment, service, and repository information:

railway status

Edit the code locally.
Redeploy your local changes to Railway:

railway up

Railway will upload the current local directory and deploy it to the linked service.

Via Git / GitHub

Use this workflow if you want to manage changes through GitHub and let Railway automatically redeploy after every push.

Deploy the template.
Open Source Repo or Upstream Repo from the Railway dashboard.
Fork the repository to your own GitHub account.
Clone your fork locally:

git clone your-fork-url
cd your-project-directory

Edit the code locally.
Commit and push your changes to your fork:

git add .
git commit -m "Customize Selenium Flask template"
git push origin main

In Railway, change the service Source Repo to your fork if Railway does not automatically create or link it.
After the service is connected to your fork, future pushes to the repository can trigger automatic redeployments.

Common Use Cases

Trigger automated browser tasks via REST API
Scrape JavaScript-heavy websites
Build internal scraping workers
Run scheduled browser automation jobs
Create lightweight data extraction APIs
Test browser flows through remote Chrome sessions
Integrate browser automation with n8n, cron jobs, webhooks, or backend systems

Dependencies for Selenium with Flask Hosting

Flask REST API Service

Python
Flask
Selenium Python package
Gunicorn or another Python WSGI server

Selenium Service

Selenium Standalone Chrome
Headless Chrome
Remote WebDriver endpoint

Deployment Dependencies

This template uses two Railway services:

Flask REST API service
Selenium Standalone Chrome service

Recommended Selenium image:

selenium/standalone-chrome

Recommended Remote WebDriver endpoint:

http://standalone-chrome.railway.internal:4444/wd/hub

Environment Variables

Flask Service

PORT=5000
SELENIUM_REMOTE_URL=http://standalone-chrome.railway.internal:4444/wd/hub

Use the public Selenium Railway URL if running Flask locally:

SELENIUM_REMOTE_URL=https://your-selenium-service.up.railway.app/wd/hub

Selenium Standalone Chrome Service

PORT=4444
START_XVFB=true
SE_SCREEN_WIDTH=1920
SE_SCREEN_HEIGHT=1080
SE_SESSION_TIMEOUT=300
SE_NODE_CHROME_ARGS="--disable-dev-shm-usage --no-sandbox --disable-gpu --disable-extensions --disable-infobars --window-size=1920,1080 --headless=new --remote-allow-origins=*"
SE_NODE_MAX_SESSIONS=4
SE_NODE_SESSION_TIMEOUT=300
SE_NODE_OVERRIDE_MAX_SESSIONS=true

Implementation Details

The Flask service connects to Selenium using Remote WebDriver. The remote URL is configured through the SELENIUM_REMOTE_URL environment variable.

Recommended Railway internal URL:

http://standalone-chrome.railway.internal:4444/wd/hub

For each scraping request, the Flask API should create a remote Selenium browser session, run the automation logic, close the browser session, and return a JSON response.

A good request lifecycle is:

Receive HTTP request in Flask.
Create remote Selenium browser session.
Open target page.
Extract required data.
Close the browser session.
Return JSON response.

Keep browser sessions short-lived and always close them after each request to avoid memory buildup or stuck Chrome sessions.

Private vs Public URL

Use Railway private networking when the Flask service and Selenium service are deployed inside the same Railway project.

Private Railway URL:

http://standalone-chrome.railway.internal:4444/wd/hub

Use the public Selenium Railway URL when connecting from your local machine or from outside Railway.

Public Railway URL:

https://your-selenium-service.up.railway.app/wd/hub

The .railway.internal domain is only reachable from services running inside Railway. It is not accessible from your local computer.

Why Deploy Selenium with Flask on Railway?

Railway is a singular platform to deploy your infrastructure stack. Railway will host your infrastructure so you do not have to deal with complex server configuration, while still allowing you to scale services vertically and horizontally.

By deploying Selenium with Flask on Railway, you get a clean two-service architecture for browser automation. The Flask API stays lightweight, while Selenium runs separately as a dedicated remote browser service.

This makes the template practical for scraping APIs, automation workers, internal tools, webhook-based browser tasks, and integrations with platforms like n8n or other backend systems.