Decode hex string to bytes: from_hex

The from_hex filter converts a hexadecimal string into a bytes object. Each pair of hex characters in the input string is converted to a single byte. For example, “48656c6c6f” decodes to the bytes representing “Hello”.

This is useful when working with IoT devicesA device is a model representing a physical or logical unit that contains entities. and protocols that represent binary data as hex strings. Many BLE (Bluetooth Low Energy) sensorsSensors return information about a thing, for instance the level of water in a tank. [Learn more], Zigbee devices, and serial protocols report their data as hexadecimal strings. The from_hex filter converts these hex strings into bytes that you can then process further with unpack to extract numeric values, or decode to a text string.

Usage

Here’s how to use this template function. Copy any example and adjust it to your setup.

{{ "48656c6c6f" | from_hex }}

b'Hello'

Function signature

The signature is a technical summary of this template function. It shows the name of the function, the values (called parameters) it accepts, and what type of data each parameter expects (for example, a piece of text or a number).

Function parameters that have a = with a value after them are optional. If you leave them out, the default value shown is used automatically. Function parameters without a default are required.

value | from_hex() -> bytes

Function parameters

The following parameters can be provided to this filter.

Good to know

• The input must have an even number of hex characters. Odd-length strings raise an error.
• The result is raw bytes. Pipe to string for text, or unpack for numeric values.
• A 0x prefix on the input raises an error; strip it first.

Try it yourself

Ready to test this? Open Developer tools > Template, paste the example into the Template editor, and watch the result update on the right. Edit the values to see how the function adapts to your own entitiesAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more].

More examples

Real scenarios where this function comes up in automations and templates. Copy any example and adapt it to your setup.

Decode a hex sensor value to an integer

Convert a hex string from a sensor into an integer using unpack.

{{ "04d2" | from_hex | unpack(">H") }}

1234

Decode hex to a text string

Convert a hex-encoded string to readable text by decoding the resulting bytes.

{{ "486f6d65" | from_hex | string }}

Home

Process BLE advertisement data

Extract a temperature value from a BLE sensor that reports data as a hex string. The first two bytes (4 hex characters) contain the temperature as a big-endian signed short.

{% set hex_data = states("sensor.ble_advertisement") %}
{{ hex_data[:4] | from_hex | unpack(">h") / 100 }}

21.5

Still stuck?

The Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with your template and expected result, or share on our subreddit /r/homeassistant.

Related template functions

These functions work well alongside this one:

• Pack value to bytes: pack - Packs a value into bytes using a Python struct format string.

• Unpack bytes to value: unpack - Unpacks bytes into a value using a Python struct format string.

• Decode from base64: base64_decode - Decodes a base64-encoded string.