How We Verified 51 RL Environments (and What We Learned)

Most "awesome RL" lists are link collections nobody maintains. We wanted rlenvlab's directory to be different: every repo link verified live, every paper link checked, maintenance status derived from real commit history. Here's exactly how we did it — and the traps we found along the way.

The pipeline

1. Repo existence via the GitHub API. Every one of the 45 unique repos was checked live. No guessing from memory, no trusting old READMEs.
2. Redirect resolution. GitHub orgs move. We followed redirects to canonical names: deepmind/* became google-deepmind/*, and HighwayEnv and D4RL now live under Farama-Foundation/.
3. Maintenance from pushed_at. "Maintained" means a commit within the last 12 months — not vibes. This caught repos that look alive but haven't been touched in years.
4. Paper links verified against arXiv. Every arXiv ID was checked for existence and title match before linking.
5. Star counts as integers. Real current numbers from the API, not rounded figures copied from blog posts.

What we caught

The arXiv check paid for itself immediately: 7 of our 11 uncertain paper IDs turned out to be completely different papers — our guessed "MuJoCo Playground" and "Isaac Lab" IDs pointed at unrelated work. Those entries ship with no paper link rather than a wrong one. We also caught a 404 on what we thought was the Overcooked-AI repo — the real one uses an underscore (overcooked_ai), not a hyphen. These are exactly the errors that accumulate silently in unmaintained lists.

What the data taught us

• 34 of 51 environments are maintained — a healthier ratio than the ecosystem's reputation suggests, thanks largely to Farama's stewardship.
• The graveyard is real but specific: OpenAI Retro, DeepMind Lab, NLE, SMAC, RLCard, and PySC2 are archived or stale. If your tutorial pins one of these, budget time for dependency archaeology.
• Surprises cut both ways: Microsoft's AirSim looked dead but shows commits from September 2026. Reputation is a lagging indicator; commit history isn't.

Keeping it honest

Verification isn't a one-time event — it's a cadence. Our checking scripts live alongside the dataset, and we re-verify on a monthly cycle as part of the changelog. If you spot a dead link or a repo we've misjudged, that's a data bug, and we'd rather hear about it than host it.

Browse the result: the directory, all 51 environments, every link checked.