The slider varies the datastream value between the datastream’s min/max values based on the slider’s horizontal position. It is similar in the way a potentiometer is used to vary resistance based on its position.


Select or create a datastream of data type integer or double. Widget properties (label, color, etc.) are also changed via the datastream, but only for virtual, enumerable, and location pins, not digital and analog pins.

Widget Controls

The widget has the following controls:
Send on release: Enable to limit updating the assigned datastream value only when the control is released by the user.

How to process widget input on the device

When the control is pressed, value is sent and stored into the Blynk.Cloud. After that it's sent to your device.

Reading the widget value

For example, if Slider widget is set to Datastream with Virtual Pin V1, you can use such code:
BLYNK_WRITE(V1) // this command is listening when something is written to V1
int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable
if (pinValue == 1){
// do something when the control is pressed;
} else if (pinValue == 0) {
// do something when the control is released;
Serial.print("V1 value is: "); // printing value to serial monitor

Changing the datastream value

You can update the assigned datastream value using the hardware or HTTP API.
Blynk.virtualWrite(vPin, 1);
https://{server_address}/external/api/update/?token={your 32 char token}&V0=1
https://{server_address}/external/api/batch/update/?token={your 32 char token}&V0=1
Don't put Blynk.virtualWrite()into the void loop() as it can cause a flood of messages and your hardware will be disconnected. Send such updates only when necessary, use flags, or timers.
Sketch: Basic Sketch
Sketch: Set Property
Sketch: VirtualPinWrite
Sketch: VirtualPinRead

Change Widget Properties

You can change certain properties of the Widget from your hardware. For that, use this command:
Blynk.setProperty(vPin, "widgetProperty", "propertyValue");
  • vPin is: virtual pin number the widget is assigned to
  • widgetProperty: property you want to change
  • propertyValue: value of the property you want to change
Don't put Blynk.setProperty()into the void loop() as it can cause a flood of messages and your hardware will be disconnected. Send such updates only when necessary, or use timers.

Properties you can change

You can change the properties color, label, isDisabled, isHidden of the widget from your hardware, or via an HTTP API. The color hexadecimal values in the HTTP API URL must include the hash # character urlencoded as %23.

Set a custom label for the widget

Blynk.setProperty(V1, "label", "Status");


Blynk.setProperty(V1, "isHidden", true);
Widget will be hidden from dashboard. Design your UI so that it doesn't look weird when there is no widget.


Blynk.setProperty(V1, "isDisabled", true);
Widget will be greyed out on UI and users won't be able to tap on it.

Set a color for the widget

Blynk.setProperty(V1, "color", "#73D13D"); // green
Blynk.setProperty(V1, "color", "#ED9D00"); // orange

Change widget properties via HTTPs API

/external/api/update/property?token={your 32 char token}&pin={your vPin}&{property}={value}
Updates the Datastream Property and all assigned Widgets

Sync to the latest known state

You can update your hardware to the latest datastream value from Blynk.Cloud after your hardware went offline, and then came online again. Use Blynk.syncVirtual() to update a single virtual pin, or Blynk.syncAll() to update all virtual pins. See State Syncing for more details.
// Called when hardware is connected to Blynk.Cloud
// get the latest value for V1
// Request Blynk server to re-send latest values for all pins