Level Slider

Displays a vertically filled level for the last datastream value, and sets a new value when the user taps and drags the level control. The number of level segments displayed and selectable are adjustable by the widget settings. It combines functions of Level V and Slider.


Select or create a datastream of data type integer or double.

Widget Controls

The widget has the following controls:

  • Level Handle: Drag the level handle to adjust the level.

Widget Settings

  • Use datastream’s Min/Max - The min/max range of the slider is constrained to the datastream min/max values when this is enabled, otherwise the user may enter specific values (make sure they are within the range of the assigned datastream min/max).

  • NUMBER OF SEGMENTS - defines visually how the levels are displayed relative to the latest datastream value, and the step behavior of the level handle when the number of segments is specified between 3 and 10. The ‘Fill’ option will use a continuous range between the min/max specified by ‘MIN/MAX VALUES’.

  • Send on release - when enabled, the selected value is sent when the user releases the control, otherwise it is continuously sent until released by the user (not recommended).

How to process widget with the hardware

Reading the widget value

For example, if Level Slider widget is set to Datastream with Virtual Pin V1, you can use such code:

// Called when the datastream V1 value changes

// Assign incoming value from pin V1 to a variable
// according to the datastream data type
int pinValue = param.asInt(); 
// double pinValue = param.asDouble();

if (pinValue == 0){
  // do something when the value is 0
} else if (pinValue > 0 && =< 128) {
  // do something when the value is between 1 and 128
} else {
  // print value to serial monitor
  Serial.print("V1 value is: "); 


Changing the datastream value(s)

You can set the state of the widget by updating the assigned datastream value using the hardware or HTTP API. For a datastream V1 assigned data type of integer, double, or enum:


Blynk.virtualWrite(V1, 1);


https://{server_address}/external/api/update/?token={your 32 char token}&V1=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 label, color, isDisabled, isHidden of the widget from your hardware, or via an HTTP API. The URL must be encoded, so spaces in labels must be replaced with %20, and color hexadecimal values in the HTTP API URL must include the hash # character urlencoded as %23.

Change Widget Label

Blynk.setProperty(V1, "label", "Air temperature");

Set Widget Color

Works only if the gradient was not set for this widget.

//#D3435C - Blynk RED 
Blynk.setProperty(V1, "color", "#D3435C");


Widget will be greyed out on UI and users won't be able to tap on it.

Blynk.setProperty(V1, "isDisabled", 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, "isHidden", true);

Change widget properties via HTTPs API

Updates the Datastream Property and all assigned Widgets

GET https://{server_address}/external/api/update/property?token={your 32 char token}&pin={your vPin}&{property}={value}

The endpoint allows you to update the Datastream Property value via GET request. All widgets (both web and mobile) that are assigned to this datastream will inherit this property. The Datastream Property is persistent and will be stored forever until you change it with another value. In order to clear the property you need to clear the device data in device actions menu.

Example: https://blynk.cloud/external/api/update/property?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&pin=V2&label=My%20Label



Path Parameters


{server address}*


Get from the bottom right of your Blynk console. More information.

Query Parameters




Device auth token from Device info



The datastream virtual pin (should start with "v")



The property of the widget you want to update: label, color, isDisabled, isHidden



the text used as widget label



button color hexadecimal, must include the hash # character urlencoded as %23. Works only if the gradient was not set for this widget.



true or false



true or false

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

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