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Introduction

To develop and host a Ruby on Rails application on Square Cloud, it’s essential to follow a structured sequence of configurations and prerequisites. This technical guide will cover the entire process, from initial setup to production deployment.

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Prerequisites

  • Square Cloud Account: Register through the signup page using your email.
  • Active plan: Ensures dedicated resources and optimized performance for your application. Check our available plans and choose the most suitable for your needs.
This guide runs on the Ruby runtime.

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Create the project

You need Ruby and Bundler on your machine. If you don’t have Ruby yet, download it from the official Ruby website. Install Rails and create a project:
New Rails projects use SQLite, stored in the storage/ folder, so they run without an external database. Start the development server:
Rails listens on http://localhost:3000 in development. Keep the default port on your machine: you don’t need port 80 locally.

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Build for production

Square Cloud prepares the app when it starts: it runs bundle install to install the gems in your Gemfile, then your START command precompiles the assets and prepares the database. The Ruby runtime sets RACK_ENV=production, so Rails runs in production mode.

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Port and host

Nothing to change: rails server reads the PORT environment variable, which Square Cloud sets to 80, and in production it listens on all network interfaces.

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Environment variables

Set these environment variables in the dashboard or with squarecloud app env set:

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Configure Square Cloud

Create a squarecloud.app file at the root of your project:
squarecloud.app
On every start, this command:
  • removes a server PID file left by a previous run, which would stop Rails from starting;
  • rails assets:precompile builds your CSS and JavaScript into public/assets;
  • rails db:prepare creates the databases or applies pending migrations;
  • rails server starts Puma.
RUNTIME=ruby selects the Ruby runtime without a MAIN file. The commands use bundle exec rails instead of bin/rails because a ZIP made on Windows can lose the permission to execute bin/rails.

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What goes in the ZIP

  • Your whole project: app/, bin/, config/, db/, lib/, public/, Gemfile, Gemfile.lock and config.ru.
  • squarecloud.app.
Leave out config/master.key (the key goes in RAILS_MASTER_KEY), log/, tmp/ and the local databases in storage/.

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Deploy and verify

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Via dashboard

1

Access the Upload Page

Access the upload page and upload your project zip file.
2

Configure Your Environment

After uploading your zip, you will need to configure the name, main file or runtime environment and other settings for your project.
If you are uploading a web project, make sure to select “Web Publication” and set a subdomain to your project.
3

Deploy Your Project

Finally, click on the “Deploy” button to host your project on Square Cloud.
After deployment, you can monitor your project’s status and logs from the dashboard.
Uploading application to Square Cloud
4

Confirm Your App Is Live

Your first deploy usually takes less than a minute. In the dashboard, wait for your application status to show as running and check the logs for any startup errors.
If you deployed a website or API, open https://<your-subdomain>.squareweb.app in your browser: you should see your application responding. If you deployed a bot, send it a command to confirm it is online.
App not starting? See the Troubleshooting guide for the most common causes and fixes.

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Via CLI

To use this method, your project needs a configuration file named squarecloud.app at its root. It tells Square Cloud how to run your application.

Configuration file guide

Learn how to create the squarecloud.app configuration file that defines your application’s environment.
1

Install the CLI

Install the Square Cloud CLI. If you already have it, run the same command to update it:
2

Log In

Run the command below. It opens your browser: approve the login there and the CLI is ready. There is no API key to copy. For scripts and CI, see CLI authentication.
3

Upload Your Project

From your project folder, run the command below. The CLI zips the current folder, leaving out what squarecloud.ignore lists, and uploads it:
To upload a zip you created yourself, pass it with --file:
4

Confirm Your App Is Live

Your first deploy usually takes less than a minute. Check your application status and logs directly from the terminal:
If you deployed a website or API, open https://<your-subdomain>.squareweb.app in your browser: you should see your application responding. If you deployed a bot, send it a command to confirm it is online.
App not starting? See the Troubleshooting guide for the most common causes and fixes.

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Common errors

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Custom Domain

To use a custom domain (e.g., mysite.com) instead of the default URL mysite.squareweb.app, you need the Standard plan or higher. The default URL comes from the SUBDOMAIN field in the configuration file. To connect your domain, follow how to set up your own domain.

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Minimum RAM Requirements

Minimum: 512MB RAM for websites and APIs, enough for a static build on the static runtime. For apps that render pages on a server (Next.js, Nuxt, Angular SSR and similar), we recommend at least 1GB RAM. For larger applications, allocate more RAM to prevent the application from running out of memory and crashing.

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Could not find this site.

Check if the subdomain/domain matches what’s configured in the SUBDOMAIN field or in the custom domain settings. If you just uploaded the site, wait up to 60 seconds for Square to enable first access.

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Site took too long to respond…

Your server must listen on port 80 and host 0.0.0.0. Square Cloud sets the PORT (80) and HOST (0.0.0.0) environment variables in your application: read them in your code instead of hardcoding other values. A server that listens only on localhost or 127.0.0.1 never receives requests.

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Missing secret_key_base or ActiveSupport::MessageEncryptor::InvalidMessage

RAILS_MASTER_KEY is missing or does not match config/credentials.yml.enc. Copy the content of the config/master.key that created those credentials, then restart the application.

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Next steps

Environment variables

Keep secrets and settings out of your code and read them at runtime.

Custom domain

Serve your app on your own domain, on the Standard plan and above.

Troubleshooting

Fix an app that does not start or a site that does not respond.
For more about Rails, see the official Rails guides.

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Contact us

If you continue facing technical difficulties, our specialized support team is available to assist you. Contact us and we’ll be happy to help you resolve any issue: support quality is a big part of why developers rate Square Cloud 4.9/5 across 402 reviews on Google and Trustpilot.