OpenTTD Modding on OpenMods

OpenTTD's fully-open-source modding heritage

OpenTTD (2003 first release, ongoing) is the open-source reimplementation of Transport Tycoon Deluxe. The modding architecture is unique on this list: OpenTTD is fully open-source, the modding "API" is the game's source code itself, and the community has built a rich ecosystem of NewGRFs (graphics replacements), AI/GS scripts (Squirrel-based logic), and scenarios.

The community runs bananas.openttd.org as the canonical content hub, integrated into the in-game launcher.

The toolchain

• In-game Online Content: built-in browser pulling from bananas.openttd.org.
• NewGRF format: for graphics replacements (locomotives, road vehicles, stations, terrain).
• GameScript / AI Script (Squirrel): for behaviour mods.
• Scenarios: pre-built starting situations.

What you'll find on OpenMods

OpenTTD content lives overwhelmingly on bananas.openttd.org and the in-game browser. GitHub hosts OpenTTD itself plus NewGRF authoring tools. OpenMods catalogues whatever GitHub-published OpenTTD content exists.

Practical notes

• Open-source game. You can read the source if you want to understand any behaviour.
• In-game content browser is the canonical install path. Settings → Online Content.
• NewGRFs change graphics, AI/GS change behaviour. Two distinct mod categories.
• Multiplayer is well-supported. OpenTTD's multiplayer infrastructure is mature.