user51587: I'm unable to access the first led in my strip with this code:
void loop()
{
  leds[0] = CRGB::White; FastLED.show(); delay(100);
  leds[0] = CRGB::Black; FastLED.show(); delay(100);
}

Instead, it blinks 3 leds, though I expect it to blink only the first one.

Here's how my setup code looks like:
#define DATA_PIN    1
#define CLK_PIN   5
#define LED_TYPE    WS2812B
#define COLOR_ORDER RGB
#define NUM_LEDS    60
CRGB leds[NUM_LEDS];

#define BRIGHTNESS          10

void setup() {
  delay(1000); // Power-up delay

  // tell FastLED about the LED strip configuration
  FastLED.addLeds<LED_TYPE,DATA_PIN,COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);

  // set master brightness control
  FastLED.setBrightness(BRIGHTNESS);
}

The led was bought from here: https://www.aliexpress.com/item/0-5-5M-30-60-LEDs-M-2811-Pixels-Programmable-Individual-Addressable-LED-Strip-light-WS2811/32849630888.html?spm=a2g0s.9042311.0.0.8e664c4dU4dru2

user27653: The description in the link of where you bought the strip says:

Description:

LED Type: 5050SMD with External IC WS2811 （1 IC control 3leds）


So, this is probably as intended.
Note the application circuits in the datasheet for the controller IC (WS2811) [Page 5] where, for 5V, you can address a single LED, but for a 12V configuration, you must group the LEDs in sets of 3.


51587: <p>I'm unable to access the first led in my strip with this code:</p>

<pre><code>void loop()
{
  leds[0] = CRGB::White; FastLED.show(); delay(100);
  leds[0] = CRGB::Black; FastLED.show(); delay(100);
}
</code></pre>

<p>Instead, it blinks 3 leds, though I expect it to blink only the first one.</p>

<p><a href="https://i.stack.imgur.com/iAfuX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iAfuX.jpg" alt="enter image description here"></a></p>

<p>Here's how my setup code looks like:</p>

<pre><code>#define DATA_PIN    1
#define CLK_PIN   5
#define LED_TYPE    WS2812B
#define COLOR_ORDER RGB
#define NUM_LEDS    60
CRGB leds[NUM_LEDS];

#define BRIGHTNESS          10

void setup() {
  delay(1000); // Power-up delay

  // tell FastLED about the LED strip configuration
  FastLED.addLeds&lt;LED_TYPE,DATA_PIN,COLOR_ORDER&gt;(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);

  // set master brightness control
  FastLED.setBrightness(BRIGHTNESS);
}
</code></pre>

<p>The led was bought from here: <a href="https://www.aliexpress.com/item/0-5-5M-30-60-LEDs-M-2811-Pixels-Programmable-Individual-Addressable-LED-Strip-light-WS2811/32849630888.html?spm=a2g0s.9042311.0.0.8e664c4dU4dru2" rel="nofollow noreferrer">https://www.aliexpress.com/item/0-5-5M-30-60-LEDs-M-2811-Pixels-Programmable-Individual-Addressable-LED-Strip-light-WS2811/32849630888.html?spm=a2g0s.9042311.0.0.8e664c4dU4dru2</a></p>
 27653: <p>The description in the link of where you bought the strip says:</p>

<blockquote>
  <p>Description:</p>
  
  <ol>
  <li>LED Type: 5050SMD with External IC WS2811 （1 IC control 3leds）</li>
  </ol>
</blockquote>

<p>So, this is probably as intended.</p>

<p>Note the application circuits in the <a href="https://cdn-shop.adafruit.com/datasheets/WS2811.pdf" rel="nofollow noreferrer">datasheet for the controller IC (WS2811)</a> [Page 5] where, for 5V, you can address a single LED, but for a 12V configuration, you must group the LEDs in sets of 3.</p>

<p><a href="https://i.stack.imgur.com/kOXy2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kOXy2.png" alt="enter image description here"></a></p>
