The most significant development in DSi firmware history is . This is a "bootloader exploit" that is installed directly to the DSi’s internal NAND memory.
Unlike the original DS or DS Lite, the DSi has an internal operating system that can be updated. Nintendo released several official updates between 2008 and 2011. The final version is (released in June 2012 for PAL/NA regions and slightly later for Japan). Nintendo Dsi Firmware Download
The final official firmware released for the Nintendo DSi was , launched in December 2012. You can check your current version by looking at the numbers on the bottom right corner of the top screen while in the System Settings menu. Understanding Custom Firmware (Homebrew) The most significant development in DSi firmware history is