If you have come to this page from another article on the site, an MLO is a custom interior environment in GTA. That's the short version. Everything else here is detail.
We keep this page short on purpose. It is a glossary anchor - a small, accurate definition that other articles can link to without having to re-explain the concept every time.
What MLO stands for
MLO stands for Multi Loaded Object - sometimes Map Loaded Object in older community discussion. The acronym has drifted in usage and you will see different expansions in different places. The meaning, in practice, has converged: an MLO is a custom interior that the game loads when the player passes through a portal door.
The term comes out of the GTA IV / GTA V modding scene. It is not a Rockstar term. Rockstar's own internal interiors work via similar mechanisms but are not labelled MLOs in any official material.
What an MLO actually does
When the player walks through a doorway tagged as an MLO portal, the game switches the rendered interior space from whatever was there before (often a stub interior or nothing) to a custom environment built by a modder. The interior can be radically different from what the exterior facade suggests - in a sense, MLOs let modders ship pocket dimensions inside an unchanged exterior world.
Most MLOs are interiors of buildings: police stations, hospitals, bars, custom businesses, the standard furniture of a roleplay server. Some are larger - underground tunnels, hidden labs, secret bunkers.
How MLOs are made
The typical workflow: the modeller builds the interior in 3ds Max or Blender, exports it via plugins that produce GTA-compatible asset files, then uses CodeWalker to wire it into the map. Collisions, lighting and audio occlusion all need separate work. A serious MLO takes weeks - good ones take months.
We don't ship a step-by-step here because tooling changes regularly and a tutorial would go stale. The process exists; it is well-documented in the community; the tools are mature.
Where MLOs live
Mostly on FiveM. The single-player modding scene uses MLOs sparingly because installing them in single-player requires specific care and is more fragile than texture or vehicle mods. FiveM servers, by contrast, ship MLOs as part of the server bundle - the player downloads them automatically when joining. A typical large RP server has dozens of MLOs in active use.
MLOs are also a category in the gtamodding.net catalogue and in various marketplaces. We do not host MLO downloads on this site - we are the editorial layer above the catalogue, not a redistribution host.
Why MLOs matter for GTA 6
If GTA 6's PC release follows the historical pattern, and if the underlying engine is a recognisable evolution of GTA 5's RAGE branch, MLOs will be one of the first serious mod categories to mature. The reasoning is simple: interior modding requires less foundational toolwork than exterior modding does, and the demand from RP servers is enormous. We discuss this expectation specifically in the MLO future piece - it is, of course, speculative.