What Are YMAP Files?
YMAP files are the map placement format used by GTA V and FiveM to define where objects, buildings, and props exist in the game world. When you create a custom interior or map modification for FiveM, you are essentially creating a YMAP file that tells the engine which 3D models to place, where to position them, and how to orient them. Unlike simple prop placement scripts that spawn objects at runtime, YMAP files are loaded as part of the game world during streaming, which means they benefit from the engine's built-in level of detail system, occlusion culling, and memory management. This makes YMAP the preferred method for creating permanent map additions that need to perform well on servers with many players.
Tools for Map Development
The primary tool for creating FiveM maps is CodeWalker, a free community-developed application that allows you to browse, edit, and export GTA V map data. With CodeWalker, you can place props from the game's built-in library, position them precisely using coordinates and rotation values, and export your creation as a YMAP file ready for streaming. For more advanced work, Blender with the Sollumz addon allows you to create entirely custom 3D models and export them in the formats FiveM requires. Many map developers also use in-game tools like Spooner or custom prop placement scripts for initial layout work before exporting to YMAP format. The workflow typically involves rough placement in-game, refinement in CodeWalker, and final export for production use.
Creating Custom Interiors
Custom interiors are enclosed spaces like apartments, offices, shops, or underground facilities that players can enter and interact with. Creating a convincing interior requires attention to collision geometry, lighting, and prop density. Start by defining the shell of your interior using appropriate wall, floor, and ceiling models, then add furniture, decorations, and functional elements. Collision files (YBNF) must match your visual geometry so players cannot walk through walls or fall through floors. Interior lighting is handled through a combination of baked light probes and dynamic light sources defined in your YMAP. Test your interior thoroughly by walking through every corner, checking for visual seams, collision gaps, and areas where the camera clips through geometry.
Streaming and Performance
Custom maps are streamed to players as they approach the location, which means file size and complexity directly impact loading times and client performance. Keep your YMAP files focused on a reasonable area rather than spreading props across the entire map in a single resource. Large interiors should be split into multiple YMAP files that load independently, and you should use appropriate LOD distances to prevent distant props from consuming rendering resources. The fxmanifest.lua for a map resource needs to include your YMAP and YTYP files as data_file entries with the correct type declarations. Monitor client-side performance using FiveM's built-in profiler to ensure your custom maps do not cause frame rate drops, especially in areas where many players gather simultaneously.
Prop Libraries and Best Practices
GTA V ships with thousands of built-in props that you can use in your maps without adding any extra streaming content. Learning the prop naming conventions helps you find the right objects quickly. Props prefixed with prop_ are general-purpose items, v_ prefixed items are interior furnishings, and hei_ items come from heist-related content. When placing props, align them to a consistent grid to avoid floating objects and overlapping geometry. Group related props together logically and use descriptive names for your YMAP files so other developers can understand the map structure. Always test your maps with the default game lighting and weather conditions, as props can look very different under various lighting scenarios.