I've been researching this and cannot find any comprehensive guides. I'm looking to replace some incandescent bulbs soldered to pcb's inside my cars console. I've found some through-hole clear LEDs that have built-in resistors and they work but does that make them actually 12v? When I put a volt meter across the connections it reads the same output voltage as input voltage so I don't see the resistance happening. I've also looked for SMD leds with built-in resistors or 12v version but I don't think they exist. I don't really have room for resistors and looking for options.
AFAIK there is no, or at least no common, led diode that is typically 12V forward voltage by it self. 12V led are modules that consist of some combination of diodes and resistors to make them suitable for 12V power applications without needing extra current limiting. This may be a single led with resistor, or multiple LEDs with resistor, or maybe a constant current IC. Some may have extra features like reverse protection or any direction input.
But they are not bare diodes.