Cannot install older IntelliJ IDEA versions on macOS: "the disk image is corrupted"

Problem

Installing an IntelliJ IDEA version older than 2026.1 on macOS fails with the error "the disk image is corrupted". Verifying the .dmg file via Disk Utility | Verify returns:

Operation failed - image not recognised

The issue affects:

• Both Apple Silicon and Intel .dmg packages.
• Direct downloads from the official download archive.
• Installations performed via Toolbox App.

IntelliJ IDEA 2026.1 and other current builds install correctly on the same machine.

Cause

The downloaded .dmg file is corrupted in transit. The cause is typically transient — a network interruption, CDN edge issue, or browser-side download error — and is not specific to a particular IntelliJ IDEA version.

Resolution

1. Delete the existing .dmg file.
2. Re-download the installer from the official download archive, making sure to select the correct package for the Mac architecture (Apple Silicon or Intel).
3. Run the new .dmg to install.

If the re-downloaded file still fails to mount:

• Try a different browser (for example, Chrome, Firefox, or Safari).
• Try a different network connection (for example, switch from Wi-Fi to a hotspot, or vice versa).
• Compare the downloaded file size with the size shown on the download page to confirm the download completed.

Workaround

If the direct .dmg download keeps failing, install the latest patch of the required major version using Toolbox App. Toolbox App provides only the latest patch of each major release — for example, for 2025.3, only 2025.3.4 is available.