libgdx/libgdx · error · GdxRuntimeException

Cannot delete an internal file:

Error message

Cannot delete an internal file: 

What it means

GwtFileHandle.delete() unconditionally throws 'Cannot delete an internal file: <path>'. Preloaded assets are baked into the application bundle and immutable from JavaScript; the GWT backend exposes no deletion. The message text says 'internal file' because only Internal/Classpath handles can exist in this backend.

Source

Thrown at backends/gdx-backends-gwt/src/com/badlogic/gdx/backends/gwt/GwtFileHandle.java:365

	public FileHandle sibling (String name) {
		return parent().child(fixSlashes(name));
	}

	/** @throws GdxRuntimeException if this file handle is a {@link FileType#Classpath} or {@link FileType#Internal} file. */
	public void mkdirs () {
		throw new GdxRuntimeException("Cannot mkdirs with an internal file: " + file);
	}

	/** Returns true if the file exists. On Android, a {@link FileType#Classpath} or {@link FileType#Internal} handle to a
	 * directory will always return false. */
	public boolean exists () {
		return preloader.contains(file);
	}

	/** Deletes this file or empty directory and returns success. Will not delete a directory that has children.
	 * @throws GdxRuntimeException if this file handle is a {@link FileType#Classpath} or {@link FileType#Internal} file. */
	public boolean delete () {
		throw new GdxRuntimeException("Cannot delete an internal file: " + file);
	}

	/** Deletes this file or directory and all children, recursively.
	 * @throws GdxRuntimeException if this file handle is a {@link FileType#Classpath} or {@link FileType#Internal} file. */
	public boolean deleteDirectory () {
		throw new GdxRuntimeException("Cannot delete an internal file: " + file);
	}

	/** Copies this file or directory to the specified file or directory. If this handle is a file, then 1) if the destination is a
	 * file, it is overwritten, or 2) if the destination is a directory, this file is copied into it, or 3) if the destination
	 * doesn't exist, {@link #mkdirs()} is called on the destination's parent and this file is copied into it with a new name. If
	 * this handle is a directory, then 1) if the destination is a file, GdxRuntimeException is thrown, or 2) if the destination is
	 * a directory, this directory is copied into it recursively, overwriting existing files, or 3) if the destination doesn't
	 * exist, {@link #mkdirs()} is called on the destination and this directory is copied into it recursively.
	 * @throws GdxRuntimeException if the destination file handle is a {@link FileType#Classpath} or {@link FileType#Internal}
	 *            file, or copying failed. */
	public void copyTo (FileHandle dest) {
		throw new GdxRuntimeException("Cannot copy to an internal file: " + dest);

View on GitHub (pinned to 97f4086187)

Solutions

1. On the web build, 'deletion' means removing a key from Preferences/localStorage — implement it in a platform-specific save manager.
2. Branch on Gdx.app.getType() == ApplicationType.WebGL before any delete() call in shared code.
3. Audit ported code for delete()/deleteDirectory() usage when adding the GWT target.

Example fix

// before
Gdx.files.local("saves/slot1.json").delete(); // throws on GWT

// after
if (Gdx.app.getType() == ApplicationType.WebGL) {
    Gdx.app.getPreferences("saves").remove("slot1").flush();
} else {
    Gdx.files.local("saves/slot1.json").delete();
}

// 'delete' on web means removing a storage key
if (Gdx.app.getType() == ApplicationType.WebGL) {
    Gdx.app.getPreferences("saves").remove("slot1").flush();
} else {
    Gdx.files.local("saves/slot1.json").delete();
}

static boolean canDeleteFiles () {
    return Gdx.app.getType() != ApplicationType.WebGL;
}

When it happens

Trigger: Calling delete() on a FileHandle under GwtApplication — typically save-management code that removes old save files, or cleanup code that deletes temporary files after use.

Common situations: Ported save-slot management (delete save X) that uses file deletion on desktop; cache-clearing code; shared utilities that tidy up temporary assets.

Related errors

• Cannot write to files in GWT backend
• Cannot copy to an internal file:
• Cannot move an internal file:
• FileType '
• file() not supported in GWT backend

AI-assisted analysis of libgdx/libgdx@97f4086187 (2026-08-14). Data as JSON: /api/errors/999622b63e286a6e. Report an issue: GitHub.