Understand the four labels
Valve separates Steam Deck compatibility into four categories. Verified means the game meets its criteria for an out-of-the-box experience. Playable can involve manual adjustments. Unsupported means it is not currently functional under the review. Unknown means Valve has not assessed it yet. Unknown is therefore not the same finding as Unsupported.
Read the detailed entry for the game rather than copying a badge from an older article. Compatibility assessments and game software can change. The useful question is what the current notes say about the version you intend to install.
Read for friction, not just permission
Valve’s checks consider input, display, seamless operation, and system support. Think about which of those will affect you most. A setup step might be fine at a desk and inconvenient on a train. A small text label might be technically readable while still making a long evening uncomfortable.
A compatibility category does not give you a universal battery-life result or guarantee a particular frame rate in every scene. Those require measurements with a specified game version, settings, and device. This guide does not claim to have benchmarked a game or tested a particular preset.
Change one thing at a time
Once you install a game, begin with its intended default configuration and a short representative session. If you make adjustments, note the original setting first. Test one change in the same part of the game so that a different scene does not masquerade as an improvement.
Pay attention to the whole experience: clear menus, stable controls, comfortable text, and whether a launcher requires extra input. A technically working game can still be a poor fit for the way you use a handheld. Choosing another screen for that title is a reasonable outcome.
Keep your purchase decision specific
Before buying, check the exact product, current compatibility notes, and the store’s applicable purchase terms. If you want to try a demo, verify that one is offered and remember that a demo may not represent every part of the full release. Avoid building a purchase decision around an unverified performance claim from a different system.
Save the notes that actually matter to you: whether you need a keyboard for setup, whether reading feels comfortable, and which default setting you changed. A useful personal library is one you can return to without having to solve the same small problem every time.