Even if you get an X-Ray working, Bloxd.io has server-side occlusion. You might see the diamond, but the server knows you can't pathfind to it. You will frequently hit invisible "ghost blocks" that stop your mining progress, making the X-Ray useless.
Some older videos instructed players to paste code into the browser's Developer Console (F12). This code would change the transparency of blocks in the game's memory. While this worked briefly during early beta versions of Bloxd.io, the developers have patched these exploits. X Ray Texture Pack Bloxd.io