Replace using a regex pattern: regex_replace

The regex_replace template filter replaces all occurrences of a regular expression (regex) pattern in a string with a replacement value. A regular expression is a special text pattern that describes what you are looking for; regex_replace finds every part of the string that matches and swaps it out. This works like a find-and-replace tool, but with the power of patterns instead of fixed text.

This is useful when you need to clean up or transform text from sensorsSensors return information about a thing, for instance the level of water in a tank. [Learn more] and other sources. For example, you might want to strip unwanted characters from a sensor value, reformat a phone number, remove units from a measurement string so you can convert it to a number, or clean up device names for display on a dashboard.

Usage

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

{{ "Hello 123 World 456" | regex_replace("\\d+", "N") }}

Hello N World N

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 = are usually required. A few optional parameters have no default value, so the signature shows them without a = as well. To check whether a parameter is required, look at the parameter list below the signature. Each parameter is marked as Required or Optional.

The most common optional parameter without a default value is default. The default parameter sets the value a function returns when the function can’t produce a result, for example, when float gets text that isn’t a number. If you leave out default, there is no fallback value, so most functions raise an error and the template fails. The parameter list of each function says what happens. If you set default, the function returns your value instead.

round(
    value: Any,
    precision: int = 0,
    method: str = "common",
    default: Any,
) -> float | int | Any

regex_replace(
    value: str,
    find: str = "",
    replace: str = "",
    ignorecase: bool = False,
) -> str

Function parameters

The following parameters can be provided to this function.

Removing matched text

Pass an empty string as the replacement to remove all matches from the string.

{{ "Temperature: 23.5 C" | regex_replace("[^0-9.]", "") }}

23.5

Case-insensitive replacement

Set ignorecase to true to match and replace regardless of upper or lowercase letters.

{{
  "Error: DEVICE offline"
  | regex_replace("error", "Warning", ignorecase=true)
}}

Warning: DEVICE offline

Good to know

• Replaces every occurrence, not just the first one.
• Backreferences in the replacement use \1, \2, and so on, to refer to capturing groups from the pattern.
• Passing an empty replacement deletes every match from the string.

Try it yourself

Ready to test this? Open Settings > 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.

Strip units from a sensor value

Remove non-numeric characters from a sensor state so you can use it as a number.

{{ states("sensor.wind_speed") | regex_replace("[^0-9.]", "") | float }}

15.3

Clean up a device name for display

Remove unwanted prefixes or suffixes from a device name.

{{
  "MQTT - Living Room Sensor [v2]"
  | regex_replace("^MQTT - ", "")
  | regex_replace("\\s*\\[.*\\]$", "")
}}

Living Room Sensor

Mask sensitive information

Replace digits in a phone number or account number for display purposes.

{{ "+1-555-123-4567" | regex_replace("\\d(?=\\d{4})", "*") }}

+*-***-***-4567

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:

• Match a regex pattern: regex_match - Tests if a string matches a regular expression pattern at the beginning.

• Search for a regex pattern: regex_search - Searches for a regular expression pattern anywhere in a string.

• Find all regex matches: regex_findall - Finds all occurrences of a regular expression pattern in a string and returns them as a list.

• Find regex match at index: regex_findall_index - Finds all occurrences of a regex pattern and returns the match at a specific index.