Steam says it failed to unpack the runtime. What should I check?

First check that you have some free disk space, then look for a leftover or incomplete Steam runtime download. With some Ubuntu-based package installations, Steam’s files are under ~/.steam, often in ~/.steam/steam, rather than ~/.local/share/Steam.

If you find a clearly temporary runtime download or cache, removing that one item and starting Steam again may let it download a clean copy. Don’t delete the whole Steam directory, since it can contain your library and other client data. If you’re unsure which item is safe to remove, share the exact terminal error and how Steam was installed before changing files.

The error can happen when Steam can’t download or unpack its runtime, so a network hiccup or a partial download is another possibility. If you have room on the drive, close Steam completely and try launching it again later, ideally with a stable connection.

Opening it from a terminal is useful because it shows the full error instead of silently doing nothing. The exact install method and Linux distribution matter for the next steps, so check those if retrying doesn’t help.

Before trying a different package, figure out which Steam installation you already have. The system package and a Flatpak install store files in different places, so instructions for one may not match the other. On an Ubuntu-based system, a directory under ~/.steam can be normal.

I wouldn’t switch installation types as the first fix. Start with the terminal output, available disk space, and the existing Steam files, then choose a targeted step based on what you find.