GDL Downgrader for Archicad

GDL Downgrader — convert Archicad GDL objects to a lower Archicad version.

The GDL Downgrader is a desktop application for macOS and Windows that converts Archicad library parts (.gsm) from a higher Archicad version down to a lower one — the direction Archicad itself does not offer. It is built on Graphisoft's own LP_XMLConverter, the tool shipped with every Archicad installation.

Under the hood each object goes through two steps with two different converters: it is decompiled to XML with the -compatibility flag set to the target version, then recompiled to .gsm with the target version's converter. The app finds every installed converter automatically, detects each object's source version from its header, and lets you pick the target version freely.

Whether you need a single object or an entire library, the GDL Downgrader keeps the workflow safe and predictable: nothing is overwritten without confirmation, password-protected objects stay protected, and scripts that rely on commands the target version doesn't know yet are flagged before you ship them.

• Single object or whole library — a folder is processed recursively, and the original folder structure is reproduced 1:1 in the target directory.
• Automatic source-version detection — read from each object's GSM header, so mixed-version libraries are handled per object.
• Smart converter selection — decompiling uses any installed converter new enough to read the object; the exact source-version converter is not required. An object is only flagged when it is too new for the highest installed converter.
• Free target version — every installed converter is selectable; when target equals source the object is simply recompiled without -compatibility.
• Password protection preserved — protected objects are detected during conversion and re-encrypted with the same password after the downgrade.
• Command-version safety check — scripts are scanned for GDL commands introduced after the target version (including commands used as string arguments, e.g. APPLICATION_QUERY("MEPSYSTEM", …)), and flagged in the result. The underlying list is an editable, maintainable knowledge base.
• Overwrite confirmation — existing target files are never replaced without an explicit prompt that lists the affected objects.
• Bilingual interface — switch between English and German at any time.
• Cross-platform & open source — macOS and Windows, released under the MIT license.

• Collaboration across versions — hand a library part to an office or partner still working on an older Archicad release.
• Client delivery — provide objects in the exact version your client runs.
• Consolidating mixed libraries — bring a folder containing objects from several Archicad versions down to one common version in a single pass.
• Maintaining legacy projects — reuse current content in projects that cannot be migrated to the latest Archicad.

In each case the command-version check gives you an early warning when an object depends on functionality that did not yet exist in the target version — so you can review it before it reaches the model.

Note: builds are currently unsigned. On macOS confirm the first launch via Right-click → Open; on Windows confirm the SmartScreen prompt.

• README — overview and quick start (English · Deutsch)
• User Manual — full documentation (English · Deutsch)
• Changelog — versions & release notes
• License — MIT
• Command knowledge base — gdl-command-versions.json

Downloads

• macOS (Apple Silicon): on the Downloads Tab
• Windows (installer): NSIS installer — coming soon; can be built from source on Windows in the meantime (see the build instructions in the repository).
• All releases: github.com/gdl-joe/GDL-Downgrader/releases
• Source code: github.com/gdl-joe/GDL-Downgrader