3.3v Arduino, 3.3v Flashing LED - resistor needed?

Projects General Guidance
1

I see many topics indicating a resistor is still necessary even if supply = 3.3V, and LED Vf = 3.3V. I'm having a hard time wrapping my head around that, unless they're speaking of using one as a protection measure.

But,

I have a blue LED that by itself flashes. Vf is 3.3V.

Can I hook up that to a 3.3V arduino without a resistor?

2

I have a blue LED that by itself flashes.

So what does the data sheet say?

3

As a general rule: "always use resistors".. :slight_smile:

It may be a low value one.... but still use them.

As GM says.. what does the datasheet direct you to do? (not familiar with flashing leds myself)