If you clicked through from another article on this website and want to know what an MLO is, here's your answer: an MLO is a custom interior made for GTA. That's the short explanation. Everything else on this page is just detail.
This page is intentionally kept brief. It serves as a glossary anchor - a concise, correct definition that other articles can link to instead of re-explaining the concept every time.
What MLO stands for
MLO stands for Multi Loaded Object - although you may have seen it referred to as Map Loaded Object in older forum posts. The acronym went off on its own tangent over time, and you'll find various expansions throughout the web. In practice, however, the meaning has converged: an MLO is a custom interior that the game loads when you walk through a portal door.
The term originated in the GTA IV / GTA V modding community. This is not terminology used by Rockstar themselves. Rockstar's own interiors use similar mechanisms, but they are not called MLOs in any official documentation or releases.
What an MLO actually does
When the player passes through a doorway marked as an MLO portal, the game essentially swaps the interior area being rendered (typically some placeholder interior or empty space) for a new interior custom-made by a modder. These interiors can be vastly different from what the exterior building facade may imply - in a sense, MLOs allow modders to put pocket dimensions inside an otherwise untouched exterior world.
The majority of MLOs are interiors of buildings: police stations, hospitals, bars, custom businesses, the typical staples you'd see on a roleplay server. Some are bigger: underground tunnels, secret labs, concealed bunkers.
How MLOs are made
The general process: the modeller creates the interior in 3ds Max or Blender, exports it using plugins that create GTA-compatible asset files, then imports those files into CodeWalker and hooks the interior up to the map. Collisions, lighting and audio occlusion must also be done separately. Solid MLOs can take weeks to make - good ones can take months.
We do not include a step-by-step walkthrough because tooling changes frequently and a guide would become outdated. The procedure is available; it is thoroughly documented by the community; the tools are mature.
Where MLOs live
Primarily on FiveM. MLOs are used sparingly in single-player mods because installation is finicky and less robust overall than with texture or vehicle mods. Since FiveM servers bundle MLOs with the server itself - the player downloads them automatically when joining - they are used extensively there. It's common for a sizeable RP server to use dozens of MLOs.
MLOs are also a type of item in the gtamodding.net catalogue and other marketplaces. You won't find MLO downloads hosted on this site - we are an editorial layer on top of the catalogue, not a redistribution host.
Why MLOs matter for GTA 6
Should GTA 6 get ported to PC like past instalments, and should the game be built off a familiar fork of GTA 5's RAGE engine, then MLOs will likely be one of the first major mod types to come into its own. Modding interiors needs far less groundwork than modding exteriors does, and there is massive demand from RP servers. We go into why we expect this specifically in the MLO future piece. Keep in mind, this is all conjecture.