GRF is the file extention for Ragnarok Online Game Resource Archive. This file is a sort of .zip storing all resources files from the game in its content.

Writing a loader in javascript was kind of challengeous because of some limitation:

• Memory limitation
• Binary file
• ZLIB compression
• Custom DES encryption

This viewer is now used to locate errors, help searching for files, preview files (bmp, gif, jpeg, tga, models, maps, effects) and can be used to extract some type of files.

As there is no API to write into the disk there is no way to modify the GRFs you are viewing, or extract a folder from it. That's why it's called GRF Viewer. Maybe in future, more access will be given to javascript and I'll be able to modify it.

Note: By clicking directly into the data folder, it will use the remote client files instead of the files contained in your own GRF file. Try it now !