Engines
Install O3DE from the launcher, manage installed engines, build from source, and prune what you don’t need.
The Engines page answers the question “which O3DE do I use?” — and lets you install any answer without leaving OPAL. Install as many versions as you want, keep them side by side, pin projects to specific ones, and remove the rest safely.
Each engine lives in its own directory and is registered independently in the O3DE manifest, so nothing you do to one engine disturbs another.
In this section
- Install engines — Download official releases, older versions, pre-releases, and source builds, or add your own download sources.
- Manage engines — Register an existing install, set the default, view logs, and handle invalid installations.
- Remove & prune — Remove a single engine, or prune every non-default engine at once — safely, to the recycle bin.
- Source builds — Build the engine from source, and how Script-Only mode changes what’s available.
1 - Install Engines
Download O3DE releases, pre-releases, and source builds from the launcher.
OPAL installs O3DE for you. The Engine Downloads page (reached from Engines → Download Engines) reads O3DE’s release metadata and presents every available build so you never have to browse the O3DE website for the right zip.
The Engine Downloads page
A two-pane layout: the release list on the left, release details on the right.
- Platform filter — All, Windows, Linux, macOS, plus Source. (The Source option is hidden when Script-Only mode is on.)
- Latest badge — marks the newest release for each platform.
- Search — filter the list by version, source, or platform.
- Installed / downloading indicators — each row shows whether that release is already installed or currently downloading.
Select a release to see its details, then start the install. Official-release downloads run in the Downloads queue; source builds also run through the Builds queue.
Older versions and pre-releases
- Older releases are simply lower down the list — pick any prior version.
- Pre-releases are hidden by default. Tick Show pre-releases to surface
development and stabilization/* branch builds.
Custom engine sources
Beyond the official releases, you can add your own download hosts — for example a studio’s internal engine builds.
Open Custom Engine Sources, add a host, and map its JSON release manifest:
- Name — how it appears in the UI.
- Manifest URL — the JSON release manifest.
- Field mappings — which JSON keys hold the version, download URL, and release notes.
Each custom host shows its latest version and last-updated time, and a Check for Updates action refreshes them on demand. Custom-source releases appear in the list alongside official ones.
See also
2 - Manage Engines
Register existing installs, set the default engine, view logs, and handle invalid installations.
The Engines page lists every engine OPAL knows about, with search across name, version, and path. Each engine shows its name and display version, its path, and badges for Official and Default status, plus its build status where relevant.
Add (register) an existing engine
If you already have an O3DE engine on disk, click Add Engine and point OPAL at its folder. OPAL validates the engine.json; if the folder isn’t a valid engine, it shows an “Invalid Engine” error instead of registering it.
Set the default engine
Your default engine is the one preselected when you create a new project. Click Set Default on any installed engine; the Default badge moves to it.
View an engine’s log
Each engine has a View Log action for inspecting its build or install output. See Logs for the full log viewer.
Engine settings
Open an engine’s Settings dialog to adjust its OPAL-tracked properties. Among these is an optional Editor-executable path override, useful for non-standard build layouts or pinning to a specific build configuration.
Invalid installations
If an engine’s files become invalid or go missing, OPAL surfaces an Invalid installation warning row with Remove and Redownload actions so you can recover in place.
See also
3 - Remove & Prune
Remove a single engine or bulk-prune non-default engines, safely.
Engines are large. When you no longer need one, OPAL removes it safely — to the operating system’s recycle bin / trash, not a permanent delete — and cleans it out of the O3DE manifest.
Remove a single engine
Use the Remove action on an engine (available from the engine list and from an invalid-installation warning row). OPAL confirms, moves the engine directory to the OS trash, and unregisters it from the manifest.
Prune non-default engines
To reclaim space in one pass, use Prune. This bulk-removes every non-default engine, showing a confirmation modal first. As with single removal, pruned engines go to the OS trash rather than being erased outright, so a mistake is recoverable from your recycle bin.
What happens to pinned projects
If a project was pinned to an engine you remove, the project stays in your list but flags a missing-engine state. See Project status & health for how to reassign or reinstall.
See also
4 - Source Builds
Build the O3DE engine from source, and how Script-Only mode changes what’s available.
OPAL can install O3DE either as a prebuilt binary or as a source build. Prebuilt engines are faster to get running; source builds let you patch the engine yourself. OPAL tracks which is which and only offers build actions where they make sense.
Installing a source build
On the Engine Downloads page, choose the Source platform filter (or a pre-release branch). OPAL downloads the engine source and runs the build through the Builds queue, so it’s pausable, resumable, and crash-safe like any other build.
Building and rebuilding
Source engines expose a Build action on the Engines page. Prebuilt engines don’t — the action is disabled with a “Cannot build pre-built engine” note, since there’s nothing to compile.
An unbuilt source engine is clearly marked so you know it still needs a build before projects can use it.
Script-Only mode
If you’re not compiling C++, turn on Script-Only mode (in the onboarding wizard or Settings). While it’s on, OPAL:
- Hides the Source option in Engine Downloads.
- Hides build actions on source engines.
- Notes that unbuilt source engines are unavailable in Script-Only mode.
This keeps the app focused on prebuilt, script-based work.
See also