Introduction

Handling file uploads and media storage efficiently is a crucial part of web applications. Ruby on Rails provides ActiveStorage, a built-in solution that simplifies file uploads, supports cloud storage services, and integrates well with image processing libraries.

In this guide, we’ll cover:

✔️ Setting up ActiveStorage in Rails
✔️ Uploading and retrieving files
✔️ Integrating cloud storage (AWS S3, Google Cloud, Azure)
✔️ Image transformations and processing
✔️ Optimizing performance and security

1. What is ActiveStorage?

ActiveStorage is Rails’ built-in file attachment system, introduced in Rails 5.2, to replace gems like CarrierWave and Paperclip.

✔️ Supports local and cloud storage (AWS S3, Google Cloud, Azure)
✔️ Handles direct file uploads to cloud storage
✔️ Provides easy-to-use helpers for attaching and displaying files
✔️ Supports image processing via MiniMagick or Vips

2. Setting Up ActiveStorage in a Rails App

Step 1: Install ActiveStorage

Run the following command to generate ActiveStorage tables:

rails active_storage:install  
rails db:migrate

This creates tables (active_storage_blobs, active_storage_attachments) to store metadata about uploaded files.

Step 2: Configure Storage Service

Modify config/storage.yml to define storage services.

✔️ Local Storage (default)

local:  
service: Disk  
root: storage

✔️ Amazon S3 Storage

amazon:  
service: S3  
access_key_id: <%= ENV["AWS_ACCESS_KEY_ID"] %>  
secret_access_key: <%= ENV["AWS_SECRET_ACCESS_KEY"] %>  
region: us-east-1  
bucket: my-app-bucket

Set the storage service in config/environments/production.rb:

config.active_storage.service = :amazon

3. Attaching Files to Models

To allow file uploads, use the has_one_attached or has_many_attached helper in models.

Single File Upload Example
class User < ApplicationRecord  
has_one_attached :avatar  
end
Multiple File Upload Example
class Post < ApplicationRecord  
has_many_attached :images  
end

4. Uploading Files in Controllers and Forms

Updating File in Controllers
def update  
@user = User.find(params[:id])  
@user.avatar.attach(params[:avatar])  
redirect_to @user  
end
File Upload Form Example
<%= form_with model: @user, local: true do |form| %>  
<%= form.file_field :avatar %>  
<%= form.submit "Upload Avatar" %>  
<% end %>

5. Displaying and Processing Uploaded Files

Rendering an Image in Views
<%= image_tag user.avatar if user.avatar.attached? %>
Generating a Variant (Resizing Images)
<%= image_tag user.avatar.variant(resize: "100x100") %>

💡 Requires MiniMagick or Vips for image processing:

gem install image_processing

6. Direct Uploads to Cloud Storage

For large file uploads, direct cloud uploads improve performance and scalability.

Enable Direct Uploads

Add this to app/javascript/packs/application.js:

import * as ActiveStorage from "@rails/activestorage"  
ActiveStorage.start()

In your form:

<%= form.file_field :avatar, direct_upload: true %>

🚀 This allows the browser to upload files directly to Amazon S3, Google Cloud, or Azure, bypassing the Rails server.

7. Securing and Optimizing File Uploads

Restricting File Types
validates :avatar, content_type: ['image/png', 'image/jpeg']
Limiting File Size
validates :avatar, size: { less_than: 5.megabytes }
Preventing Unauthorized Downloads

To serve files only to authorized users, use redirect_to:

def show  
user = User.find(params[:id])  
redirect_to user.avatar.url if user.avatar.attached?  
end

8. Cleaning Up Old Files

Unused files take up storage and should be deleted when an object is destroyed.

class User < ApplicationRecord  
has_one_attached :avatar  
before_destroy :purge_avatar

def purge_avatar  
avatar.purge  
end  
end

Conclusion

Rails ActiveStorage provides a powerful and flexible way to handle media uploads. With cloud integration, direct uploads, and processing support, it simplifies file management in Rails applications.

🚀 Next Steps:
🔹 Use ActiveStorage for file uploads and image transformations
🔹 Integrate with AWS S3, Google Cloud, or Azure
🔹 Optimize performance and security for media files