Catalog Avatar Creator lets you try on limiteds, accessories, hats, hair combos, bundles, and animation packs from the Roblox catalog without spending a Robux. When you find something you actually want to keep, you can buy it in-game and it goes straight to your Roblox inventory, same as buying from the Marketplace.
The game's other big tool is the community outfit library: over 50 million player-created looks you can browse, wear, and use as a starting point. Try one on, swap out pieces you don't like, and build from there instead of starting from nothing. Everything is controlled through a set of chat slash commands, about 23 in total, that cover avatar appearance, server types, and display tools. None of them show up in any tutorial, but typing /cmds in the chat bar lists them all.

