Creating a macOS Catalina 10.15.7 ISO requires a two-part process: downloading the official installer from Apple and using the Terminal to convert it into a bootable disk image. 1. Download the Catalina Installer
You must download the official app from the Mac App Store to ensure the file is safe and complete.
Official Link: Open the macOS Catalina download page in the Mac App Store.
Download: Click Get. This will open the Software Update pane in System Settings. Confirm: When prompted, click Download.
Location: Once finished, the file Install macOS Catalina will be in your /Applications folder. Do not run it yet. 2. Create the ISO via Terminal
Since Apple provides a .app installer rather than an ISO, you need to run these commands to "wrap" it into a disk image format usable for virtual machines (like VirtualBox or VMware).
Create a blank disk image:hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J
Mount the image:hdiutil attach /tmp/Catalina.dmg -noverify -mountpoint /Volumes/Catalina macos catalina 10157 iso download new
Flash the installer files:sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/Catalina --nointeraction
Unmount the volume:hdiutil detach /Volumes/Install\ macOS\ Catalina
Convert to ISO format:hdiutil convert /tmp/Catalina.dmg -format UDTO -o ~/Desktop/Catalina.cdr
Rename to .iso:mv ~/Desktop/Catalina.cdr ~/Desktop/Catalina.iso 3. Verify Your System
Support Status: macOS Catalina reached "End of Life" in late 2022, but recent security updates in 2026 have extended certificate validity for iMessage and FaceTime.
Requirements: Ensure you have at least 12.5 GB of free space for the installer and another 9 GB for the temporary disk image during the ISO creation process.
Compatibility: If you are trying to upgrade a live machine instead of making an ISO, you can follow Apple’s official upgrade guide. Creating a macOS Catalina 10
🚀 Pro Tip: If the App Store says your Mac is "too new" to download Catalina, you can often bypass this by using the Mist utility or downloading the .pkg directly from Apple's servers (if available).
Are you planning to use this ISO for a virtual machine or a physical Mac?
Devices > USB and enable USB 3.0 controller. Install VirtualBox Guest Additions in safe mode.darwin.iso tools for macOS guests.smc.version = "0" to your .vmx file.Yes, but only for specific use cases.
For everyone else, the macOS Catalina 10.15.7 ISO remains a vital tool for virtualization, legacy hardware, and software archival.
If you do not have access to a Mac to create the image, you may look for a pre-built ISO.
Where to look:
Safety Warning: Always verify the checksum of a downloaded ISO. If a website asks you to disable your antivirus or fill out endless surveys to get the file, avoid it. These are often scams or contain adware. No keyboard/mouse after installation
Many users specifically target 10.15.7 because it is the end-of-life (EOL) release for Catalina. Version 10.15.6 had bugs, but 10.15.7 includes critical security updates and support for the last version of iTunes features (before being fully split into Music, Podcasts, and TV apps).
Key reasons people still download this ISO:
Downloading pre-made ISO files from third-party websites (like Archive.org or tech blogs) carries risks, including corrupted files or potential malware. The safest method is to create the ISO using the official Apple installer.
Prerequisites:
Steps:
Download the Installer:
Open the Mac App Store and search for macOS Catalina, or use a trusted terminal command to fetch the installer. If the App Store no longer offers it on your machine (as Apple often hides older OS versions), you may need to use a tool like mist or installinstallmacos.py via Terminal to download the specific InstallAssistant.pkg.
Create the Disk Image: Once you have the "Install macOS Catalina" app in your Applications folder, open Terminal and run the following commands one by one:
# 1. Create a blank DMG file (approx 8GB)
hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J
# 2. Mount the DMG
hdiutil attach /tmp/Catalina.dmg -noverify -mountpoint /Volumes/Catalina
# 3. Create the installer on the mounted DMG
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/Catalina --nointeraction
# 4. Unmount the volume (do not eject yet)
hdiutil detach /volumes/Install\ macOS\ Catalina
# 5. Convert the DMG to ISO
hdiutil convert /tmp/Catalina.dmg -format UDTO -o ~/Desktop/Catalina.cdr
# 6. Rename the CDR to ISO
mv ~/Desktop/Catalina.cdr ~/Desktop/Catalina.iso
You will now have a fresh Catalina.iso file on your desktop ready for VM use.