Datastreams

Datastreams are the foundation of how Blynk handles device data. Every value a device sends or receives — a sensor reading, a switch state, a GPS coordinate — flows through a Datastream.

Each Datastream maps to a Virtual Pin and defines how that data is typed, stored, displayed, and used across the platform: in dashboards, automations, and reports.

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Data Types

Each Datastream has a data type that determines how values are stored and validated.

Data Type	Range	Typical use
Integer	−2,147,483,648 to 2,147,483,647	Switches, counters, status codes
Double	±1.7976931348623157 × 10³⁰⁸	Sensor readings, measurements
String	Up to 255 characters	Text labels, timestamps, messages
Enumerable	Integer key mapped to display labels	State machines, multi-state controls
Location	Longitude + latitude (two doubles)	GPS coordinates

If the device sends a value that doesn't match the configured data type, the server will ignore it. Out-of-range values are clamped to Min or Max.

Need to store static or semi-static device information? Use Device Metadata instead. Metadata is better suited for values that rarely change — serial numbers, install locations, configuration parameters — and doesn't consume a Virtual Pin.

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Managing Datastreams

Open Template Settings → Datastreams to see all Datastreams defined for a template.

Filtering

Use the filter tabs to narrow the list by data type: All · Integer · Double · String · Enum · Location

Table columns

The table shows key properties at a glance. Default columns:

Column	Description
Pin	Virtual Pin number (sortable)
Name	Datastream name
Data type	Integer, Double, String, Enum, or Location
Semantics	Assigned semantic tags
Min / Max	Value bounds
Default	Initial value
Units	Display unit abbreviation
Use in Automations	Whether exposed as a Condition or Action

Use the column management button at the top-right of the table to add or remove columns. Additional columns available:

Column	Description
ID	Datastream ID
Display Name	Name shown to end-users
Color	Assigned color
Notes	Notes field content
Decimals	Display decimal places
Appears As	How it appears in Automations
Automation Condition	Whether exposed as a Condition
Automation Action	Whether exposed as an Action
Data History	Storage mode (Last Value, 1 Min AVG, RAW)

Browse Presets

Click Browse Presets to add a pre-configured Datastream from Blynk's library. Presets include common IoT datapoints (temperature, humidity, battery, RSSI, etc.) with sensible defaults already filled in.

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Creating a Datastream

Click New Datastream. Enter a name or pick from the preset suggestions, then configure the settings in the panel that opens.

See Datastream Settings for a full reference of all configuration options.

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Firmware Quick Reference

Reading a value sent from the app

BLYNK_WRITE(V1) {
  int value = param.asInt();      // Integer
  float value = param.asFloat();  // Double
  String value = param.asStr();   // String
}

Sending a value to the app

Blynk.virtualWrite(V1, value);

Syncing on reconnect

BLYNK_CONNECTED() {
  Blynk.syncAll();   // Sync all Datastreams with "sync on reconnect" enabled
  // OR
  Blynk.sync(V1);   // Sync a specific pin (ignores sync setting)
}