Public and assets folders in Ruby on Rails - Step-by-Step Execution

Concept Flow - Public and assets folders

Request from browser

↓

Rails server receives request

↓

Check if file exists in /public

↓

Serve static file

↓

Send file to browser

↓

Response sent to browser

When a browser requests a file, Rails first looks in the public folder for static files. If not found, it checks the assets folder to compile and serve CSS, JS, or images.

Execution Sample

Ruby on Rails

# Browser requests /assets/logo.png
# Rails checks /public/assets/logo.png
# If found, serves directly
# Else, compiles from /app/assets/images/logo.png
# Sends file back to browser

This shows how Rails serves static files from public or compiles assets from the assets folder.

Execution Table

Step	Action	File Checked	Result	Response to Browser
1	Browser requests /assets/logo.png	-	-	Waiting
2	Rails checks /public/assets/logo.png	/public/assets/logo.png	File exists	Serve static file
3	Send file to browser	-	-	Browser receives /assets/logo.png
4	Request complete	-	-	Response finished

💡 File found in /public, served directly without asset pipeline

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
requested_path	/assets/logo.png	/assets/logo.png	/assets/logo.png	/assets/logo.png
file_location	unknown	/public/assets/logo.png	/public/assets/logo.png	/public/assets/logo.png
response_status	waiting	ready to send	sent	completed

Key Moments - 2 Insights

Why does Rails serve files directly from the public folder without compiling?

Because files in /public are static and ready to serve, Rails skips asset compilation for faster response, as shown in execution_table step 2.

What happens if the requested file is not in the public folder?

Rails then looks in the assets folder to compile the file before serving, but this is not shown here because the file was found in /public.

Visual Quiz - 3 Questions

Look at the execution table, what file path does Rails check first when a request comes in?

A /public/assets/logo.png

B /app/assets/images/logo.png

C /config/routes.rb

D /tmp/cache/assets

💡 Hint

Check Step 2 in the execution_table where Rails checks the file location

At which step does Rails send the file back to the browser?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the Response to Browser column in the execution_table

If the file was not found in /public, what would Rails do next?

A Return 404 error immediately

B Check and compile from assets folder

C Restart the server

D Ignore the request

💡 Hint

Refer to the concept_flow where No leads to checking the asset pipeline

Concept Snapshot

Rails serves static files from the /public folder first.
If not found, it compiles assets from /app/assets.
Public files are served directly for speed.
Assets folder files go through the asset pipeline.
This ensures efficient delivery of images, CSS, and JS.
Requests flow: browser -> public -> assets -> response.

Full Transcript

When a browser requests a file, Rails first looks in the public folder for that file. If the file exists there, Rails serves it directly to the browser without extra work. This makes serving static files fast and simple. If the file is not in the public folder, Rails then checks the assets folder. Files in assets are processed by the asset pipeline, which compiles and prepares them before sending. This process ensures that CSS, JavaScript, and images are optimized. The flow is: browser sends request, Rails checks public folder, if found serves file, else compiles from assets, then sends response. This helps Rails efficiently handle static and dynamic assets.