How to Add a "Compress with Caesium" Right-Click Menu Item on macOS (Using Automator)

📦 Caesium

Caesium is a macOS app for compressing images. It is a lightweight and efficient image compressor for .jpg, .png, and .bmp formats. One can download the executable from the official page here: https://saerasoft.com/caesium

📦 Caesium CLI

Caesium CLI is a command-line tool for compressing images. It is a lightweight and efficient image compressor for .jpg, .png, and .bmp formats.

Whether you're working with hundreds of images or just want a cleaner way to compress photos from Finder, Caesium CLI is a powerful, lightweight solution. This guide walks you through:

• Installing the Caesium command-line tool
• Moving it to a system-wide directory
• Creating a right-click context menu item in macOS using Automator

This method works on macOS High Sierra to Monterey (and is generally compatible up to Sonoma).

🚀 Step 1: Download the Caesium CLI

The Caesium CLI tool, called caesiumclt, is a lightweight and efficient image compressor for .jpg, .png, and .bmp formats.

📦 Download from the official source

1. Go to the official Caesium GitHub releases page:

https://github.com/Lymphatus/caesium-image-compressor/releases

2. Scroll down to the Assets section for the latest release.

3. Download the caesiumclt-macos.zip file.

📂 Step 2: Extract and Move caesiumclt to a Safe Location

Once downloaded:

1. Unzip the file (double-click on caesiumclt-macos.zip)

2. You'll see a binary file named caesiumclt

Let's move it to a safe, system-wide location so it can be used in any Terminal script.

🔐 Move it to /usr/local/bin

1. Open Terminal

2. Run the following command (you'll need your admin password):

sudo mv ~/Downloads/caesiumclt /usr/local/bin/caesiumclt

3. If it's in another folder, adjust the path accordingly.

4. Make it executable:

sudo chmod +x /usr/local/bin/caesiumclt

✅ Test the installation

1. Run:

caesiumclt --help

If you see usage instructions, you're good to go!

🧰 Step 3: Create a Context Menu Item Using Automator

You can now integrate caesiumclt into Finder using Automator Quick Actions.

🪄 Create the Quick Action

1. Open Automator (search Spotlight or go to Applications > Automator)

2. Select New Document → Quick Action

3. Configure the top of the window:

• "Workflow receives current": folders

• In: Finder

💡 Add an Shell/Bash script that launches compression

1. Search for and add "Run Shell Script"

2. Drag it into the workflow

3. Replace the default code with:

#!/bin/bash

caesium_cli_path="/usr/local/bin/caesiumclt"

for folder in "$@"; do
  output_folder="$folder/Compressed"
  mkdir -p "$output_folder"

  find "$folder" -type f \( -iname "*.jpg" -o -iname "*.jpeg" -o -iname "*.png" \) | while read -r img; do
    "$caesium_cli_path" -q 80 -o "$output_folder" "$img"
  done

  open "$output_folder"
done

💾 Save the Quick Action

1. Go to File > Save

2. Name it: Compress with Caesium

Now, this action will appear when you right-click on a folder in Finder!

🧪 Using It

1. In Finder, right-click any folder containing images

2. Choose Quick Actions > Compress with Caesium

A Terminal window will open and show:

• Compression progress for each image

• A message when finished

3. The compressed files in a new Compressed/ subfolder

🧹 Cleaning Up or Uninstalling

To delete the Quick Action:

1. Go to Finder → Press Shift + Command + G

2. Enter: ~/Library/Services

Delete the file: Compress with Caesium.workflow

✅ Final Notes

This method works without needing Xcode or advanced scripting tools.

• You can customize the compression quality (-q) in the script above.

• Works well on Intel and Apple Silicon Macs.