The user experience of applying a resource pack in Eaglercraft involves an import process. Players cannot simply drag and drop files into a directory as they might on a desktop OS. Instead, Eaglercraft provides an interface to upload the .zip file. Once uploaded, the file is stored in the browser's cache.
Warning: You cannot add new blocks (like Copper or Deepslate). Eaglercraft 1.8.8 does not have those block IDs. The game will simply ignore those texture files. eaglercraft 188 resource packs work
At its core, Eaglercraft 1.8.8 maintains strict adherence to the asset hierarchy. This means that a resource pack designed for the official Java Edition version 1.8.9 (the most common stable release of that era) will function almost identically in Eaglercraft. The pack must be structured as a .zip archive containing a pack.mcmeta file (which defines the pack description and format version) and the standard subfolders: assets/minecraft/textures/ for blocks, items, and GUI; assets/minecraft/sounds/ for audio; and assets/minecraft/models/ for JSON-based item and block model overrides. The user experience of applying a resource pack
However, if you join a public Eaglercraft server, that server may force a resource pack on you. This overrides your personal selection. You can disable this in the multiplayer settings: Options > Chat Settings > "Allow Server Resource Packs: Off" . Once uploaded, the file is stored in the browser's cache