Can I put the capacitor at the end of the LED strip?

I have an addressable LED strip, and I want to put an capacitor to avoid flickering. Would it be also work if I put it at the end of the strip?

With a strip of that length, a capacitor is less important. Yes, I think its OK to put it there.

Are you getting flickering? If so, I do not think the capacitor will make a difference. What power supply are you using? What sketch are you running? (Before you post a sketch, please read the forum guide in the "please read" sticky post, especially #7).

As a general rule you can put capacitors across the power supply anywhere you like without causing harm. That doesn't mean that some places are not better than others, just that you won't damage anything by trying. Ideally place capacitors close to the load and always put 0μ1 decoupling capacitors as close to the power pins as physically possible for any integrated circuit.

The actual reason for this capacitor is somewhat unclear.

One consideration however is that it stabilises the voltage at the point where the power cable connects to the strip, suppressing the surges which the varying current demands of the LEDs as they implement their PWM may interact and potentially resonate with the transmission line nature of the power cable. Without the capacitor, this could result in sufficient excursions of voltage to be confused with actual data, causing spurious "instructions" to the LED control chips. This could appear as flickering.

Or it could simply interfere with the real data being sent to the strip. In both these cases, the critical point to locate the capacitor is where the power and data connect to the strip, not the other end of the strip. Note that there are always individual bypass capacitors on the strip, one for each LED (control chip) in order to suppress any such effects along the strip.

Do remember that the foils on the strip have a significant resistance such that you need to provide a power feed from a heavier power cable running alongside the strip, tapping in at least every metre along and including both ends of the strip.

Are you using a 3.3V board? I saw flickering recently when I was running an LED strip with a micro:bit, which I figure was a result of the 3.3V logic when Neopixel is 5V. It worked well enough for a tinkering/crafting project but it would not have been good enough for a nicer display.

I am using a Wemos D1 mini, so yes it is 3.3V.
I did not expreienced flickering yet, but I have worked with a 2x2 ws2812b board and there was massive flickering, which could have been solved with a capacitor. Btw. I have been using a 3V3 Pro mini there.

That's why I want to add one to this project too, just in case.

OK, so a 74HCT14 to convert to 5 V logic levels for the LED strip would be a very good idea in case. A 74HC04 is a second-best option. You need to connect two gates in tandem so the data is inverted and inverted again. The unused gate inputs should be grounded of course unless you find another use for them.

Whether this was your other flickering problem however, I cannot guarantee; it may still be a code problem. It most likely was not the lack of a capacitor but could have been the logic levels.

Well, it seems to work perfect right now, but if I something occurs, I will consider you solution, thanks.