Hearts of Iron IV Modding on OpenMods

Paradox's WW2 grand strategy with a vast alternative-history mod scene

Hearts of Iron IV (2016) is Paradox's World War II grand strategy. The modding architecture is identical to EU4 and CK3, Workshop, Paradox Mods, the launcher, script-driven data, and the community's defining contribution is alternative-history total conversions: Kaiserreich (Central Powers won WWI), The New Order: Last Days of Europe (Axis won WWII), Old World Blues (Fallout setting on the HoI4 map), Millennium Dawn (modern day).

These TCs are some of the most ambitious mod projects in PC gaming. Kaiserreich and TNO each have years of content and thousands of events, often exceeding the base game's depth.

The toolchain

Identical to CK3 and EU4: Workshop / Paradox Mods + the Paradox Launcher + script files. The community Tiger linter exists for HoI4 too.

What you'll find on OpenMods

HoI4 mods live primarily on Workshop. The largest TCs (Kaiserreich, TNO) have substantial GitHub presence for their collaborative development. OpenMods catalogues GitHub-hosted HoI4 mods, typically TC code rather than smaller mods.

Practical notes

• The TC scene is the headline. Kaiserreich, TNO, Old World Blues, Millennium Dawn, Equestria at War, each is effectively a separate game running on HoI4's engine.
• TCs don't usually combine. Pick one TC per playthrough. Some have official sub-mods (e.g. Kaiserreich + a UI mod) but most are exclusive.
• Performance scales poorly with TC complexity. TNO especially is heavy, the late-game can grind to seconds-per-day on older hardware.
• DLC requirements vary. Some mods require specific DLCs; some have "no DLC required" variants.