Search for a regex pattern: regex_search

The regex_search template filter searches for a regular expression (regex) pattern anywhere in a string. A regular expression is a special text pattern that describes what you are looking for, such as “a sequence of digits” or “the word error”. It returns true if the pattern is found anywhere in the string, and false otherwise.

This is useful when you need to check whether some text contains a particular pattern, regardless of where it appears. For example, you might want to check if a sensor’s state contains a number, see if an error message mentions a specific keyword, or test whether a device’s firmware version string includes a certain format. Unlike regex_match, which only checks the beginning of the string, regex_search scans the entire string.

Usage

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

{{ "Temperature is 23.5 degrees" | regex_search("\\d+\\.\\d+") }}

true

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

Function parameters

The following parameters can be provided to this function.

Case-insensitive searching

Set ignorecase to true to find matches regardless of upper or lowercase letters.

{{ "Error: Device Offline" | regex_search("error", ignorecase=true) }}

true

Good to know

• Returns true or false, not the matched text. Use regex_findall to extract the match.
• Matches anywhere in the string. Use regex_match to require a match at the start.

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.

Check if a sensor value contains a number

Test whether a sensor state that returns text includes a numeric value.

{{ states("sensor.status_message") | regex_search("\\d+") }}

true

Filter entities by pattern in state

Use regex_search in a condition to check if a sensor’s state mentions a specific keyword.

{% if states("sensor.weather_report")
   | regex_search("rain|storm|thunder", ignorecase=true) %}
  Bad weather expected
{% else %}
  Weather looks fine
{% endif %}

Bad weather expected

Check for a version number format

Verify that a firmware version string contains a semantic version pattern.

{{ "Firmware v2.4.1-beta" | regex_search("v\\d+\\.\\d+\\.\\d+") }}

true

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.

• Replace using a regex pattern: regex_replace - Replaces all occurrences of a regular expression pattern 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.

• Test if string contains pattern: search - Template test that checks if a string contains a regular expression pattern anywhere.