Allows you to apply CSS styles to various elements of the Home Assistant frontend.

Install using HACS or see this guide.

While card-mod can be installed as a lovelace resource, some functionality1 will benefit greatly from it being installed as a frontend module instead.

To do that, add the following to your configuration.yaml file and restart Home Assistant. See card_mod resource URL section below for how to find/use this URL.

frontend:
  extra_module_url:
    - /[card_mod resource URL]

The card_mod resource URL is dependent on where/how you have installed card-mod.js.

• If you installed through HACS, this is likely similar to /hacsfiles/lovelace-card-mod/card-mod.js?hacstag=12345678901. Here hacstag=12345678901 is just an example. Your actual card_mod HACS resource URL will be different.
• If you manage resources due to using YAML mode3 or are not using HACS your resource url may be different.

When installing through HACS your Dashboard2 lovelace resource definition will be automatically added in Dashboard resources which you can access via the button below.

Example Dashboard2 lovelace resource definition when installed through HACS.

/hacsfiles/lovelace-card-mod/card-mod.js?hacstag=12345678901

In configuration.yaml add your exact resource path to frontend: extra_module_url:. NOTE: All resource paths listed here are EXAMPLES ONLY. When updating card-mod through HACS make sure to update your extra_module_url: manually to match. This is critically important as it prevents the resource being loaded twice.

frontend:
  extra_module_url:
    - /hacsfiles/lovelace-card-mod/card-mod.js?hacstag=12345678901

NOTE: If you manage your resource URLs in YAML and do not use CAST, you do not need a resource URL at all. In this case you can just use extra_module_url. It is recommended that you use a cache busting technique to assist with caching of old files on update. e.g. ...\card-mod.js?v4.0.0 updating the version when you update card-mod.

1. Installing card-mod as a Frontend module via extra_module_url will provide performance improvements to non-CAST devices e.g. enhanced speed in applying card-mod to cards, especially when using card-mod themes. Installing card-mod as a Frontend module is also required if you are using card-mod to style panels of Home Assistant which are not Lovelace dashboards, as Dashboard resources are not loaded for those panels. This includes styling the sidebar in your theme for these panels.

2. Dashboard lovelace resource definition is required to enable card-mod to be applied to dashboards on CAST devices.

3. Since Home Assistant 2026.2 YAML Dashboards can set resource_mode to either yaml or storage. When set to yaml resources are managed in yaml mode. You can set to storage to manage resources using UI and also allowing HACS to manage resources directly.

IMPORTANT:

1. Any resource definitions automatically added by HACS should be kept as is even after adding extra_module_url. This enables you to keep track when updating via HACS.
2. Whenever you alter extra_module_url you need to restart Home Assistant.
3. Starting from version 4.2.0, if a patching version mismatch is detected, both a Browser console warning and Home Assistant notification will be created listing both the card-mod version checking for duplicates, as well as the version which has already run patching code. e.g. CARD-MOD (4.2.1): hui-card already patched by 4.2.0! If the later version is earlier than the checking version, then this is a critical issue that needs to be addressed immediately as you will not be running up to date patching code. If both versions are the same, it indicates that you have duplicate resource URLs and may end up in a critical version state. For both cases, refer to the information above to implement the recommended approach for your installation. Note: Any version prior to 4.2.0 will show as unknown version as version was not tracked in patching check prior to 4.2.0.
4. If you continue to get notifications from devices regarding duplicate patching, you may need to clear the Home Assistant Frontend application cache for that device. This may happen immediately or after some time depending on what starting pages have been cached in the Home Assistant Frontend application cache. Card_mod includes a custom event to action clearing the Home Assistant Frontend application cache. See Clearing Home Assistant Frontend application cache.

• Open your card in the GUI editor
• Click the "SHOW CODE EDITOR" button at the bottom
• Add the following to the bottom of the code:

card_mod:
  style: |
    ha-card {
      color: red;
    }

You should see the text of the card turn red as you type.
You should also see a little brush icon popping up near the "SHOW VISUAL EDITOR" button. This indicates that this card has card-mod code which will not be shown in the visual editor.

Cards are styled by adding the following to the card configuration:

card_mod:
  style: <STYLES>

If the simplest form, <STYLES> is a string of CSS which will be injected into the appropriate element based on the card type. See README-application for a detailed description on where card-mod is applied in version 4, which is slightly different from previous versions.

NOTE: card-mod only works on cards that are contained by a hui-card element, or contain a ha-card element. This includes almost every card standard Home Assistant Frontend cards, and most custom cards.

For a card contained by a hui-card element, which is almost every standard Home Assistant Frontend card, styles are injected into a shadowRoot and the bottom most element is :host, though in most cases the first element in the shadowRoot is ha-card. For many custom cards which do not take advantage of the modern hui-root container, but contain a ha-card element, the styles are injected into ha-card and the bottommost element is ha-card. See README-application for more details.

TIP: Home Assistant themes makes use of CSS variables. Those can both be set and used in card-mod - prepended by two dashes:

card_mod:
  style: |
    ha-card {
      --ha-card-background: teal;
      color: var(--primary-color);
    }

Since 4.2.0, the issue that gives rise to needing prepend option should be automatically detected and applied. card-mod version 4 has the prepend option that affects where card_mod styles are injected into the shadowRoot of the card. This is not normally required. However if a card renders in a way that initially has a 'Loading...' or similar initial state, before its final state, prepend may help. When prepend is true, card_mod styles are injected using the prepend function rather than the append function. The option is added at the same level as style.

type: energy-distribution
card_mod:
  prepend: true
  style: |
    ha-card {
      background: red;
    }

Cards known to need prepend option are listed below. Generally these cards will initially have a non-card 'Loading...' state.

• energy-distribution
• energy-sankey
• energy-sources-table
• custom:alarmo-card
• custom:button-state-card
• custom:logbook-card

  type: grid
  cards:
    - type: energy-date-selection
    - type: energy-sankey
      card_mod:
        style: |
          ha-card {
            border-color: red;
          }

Card_mod styles will not show on page load as although card_mod applies, it is removed by the next render of the card.

type: grid
cards:
  - type: energy-date-selection
  - type: energy-sankey
    card_mod:
      prepend: true # <- add prepend:true here
      style: |
        ha-card {
          border-color: red;
        }

card_mod styles will show correctly on page load.

In entities and glance cards, each entity can have options. Those elements can be styled individually by adding a card_mod parameter to the entity configuration.

For those cases, the styles are injected into a shadowRoot, and the bottommost element is thus accessed through :host.

This also applies to view badges and elements in picture-elements cards.

type: entities
entities:
  - entity: light.bed_light
    card_mod:
      style: |
        :host {
          color: red;
          }
  - entity: light.ceiling_lights
    card_mod:
      style: |
        :host {
          color: green;
        }
  - entity: light.kitchen_lights
    card_mod:
      style: |
        :host {
          color: blue;
        }

With card-mod installed, the <ha-icon> element - used e.g. by entities, glance and many more cards - will set it's icon to the value found in the CSS variable --card-mod-icon (if present).

It will also set the icon color to the value found in the CSS variable --card-mod-icon-color if present. This ignores entity state, but will still dim unless you also set --card-mod-icon-dim to none.

- entity: light.bed_light
  card_mod:
    style: |
      :host {
        --card-mod-icon: mdi:bed;
      }

All styles may contain jinja2 templates that will be processed by the Home Assistant backend.

card-mod also makes the following variables available for templates:

• config - The entire configuration of the card, entity or badge - (config.entity may be of special interest)

• user - The name of the currently logged in user

• browser - The browser_id of your browser, if you have browser_mod installed

• hash - Whatever comes after # in the current URL. card-mod watches for location changes through location-changed and popstate events so templates will be rebound with the updated hash

• panel - various information about the panel in view, be it a lovelace dashboard or another panel view. panel is a dictionary containing the following panel attributes with example values shown.

  • panel.fullUrlPath: "card-mod/another-test-view"
  • panel.panelComponentName: "lovelace"
  • panel.panelIcon: "mdi:card-bulleted-outline"
  • panel.panelNarrow: true
  • panel.panelRequireAdmin: false
  • panel.panelTitle: "Card Mod"
  • panel.panelUrlPath: "card-mod"
  • panel.panelTitle: "Card Mod - Test View"
  • panel.viewNarrow: true
  • panel.viewTitle: "Test View"
  • panel.viewUrlPath: "another-test-view"

  You can debug card-mod jinja2 templates by placing the comment {# card_mod.debug #} anywhere in your template. You will see debug messages on template binding, value updated, reuse, unbinding and final ubsubscribing. Any template is kept subscribed in cache for a 20s cooldown period to assist with template application, which can bring a slight speed improvememts when switching back and forth to views, or using the same template on cards on different views.

Home Assistant makes extensive use of something called shadow DOM. This allows for easy reuse of components (such as ha-card or ha-icon) but causes some problems when trying to apply CSS styles to things.

When exploring the cards in your browsers element inspector you may have come across a line that says something like "#shadow-root (open)" (exactly what it says depends on your browser) and have noticed that elements inside that does not inherit the styles from outside.

In order to style elements inside a #shadow-root, you will need to make your style: a dictionary rather than a string.

For each dictionary entry the key will be used to select one or several elements through a modified querySelector() function. The value of the entry will then be injected into those elements.

NOTE: The modified querySelector() function will replace a dollar sign ($) with a #shadow-root in the selector.

The process is recursive, so the value may also be a dictionary. A key of "." (a period) will select the current element.

Let's change the color of all third level titles (### like this) in a markdown card, and also change it's background.

If we look at the card in the element inspector of chrome, it looks like this:

The <ha-card> element is the base, and from there we see that we need to go through one #shadow-root to reach the <h3>. That #shadow-root is inside an <ha-markdown> element, so our selector will be:

ha-markdown$

which will find the first <ha-markdown> element and then all #shadow-roots inside that.

To add the background to the <ha-card>, we want to apply the styles to the base element directly, which has the key

.

This gives the final style:

card_mod:
  style:
    ha-markdown$: |
      h3 {
        color: purple;
      }
    .: |
      ha-card {
        background: teal;
      }

NOTE: The selector chain of the queue will look for one element at a time separated by spaces or "$".
For each step, only the first match will be selected.
But for the final selector of the chain (i.e. in a given dictionary key) all matching elements will be selected. Chains ending with $ is a special case for convenience, selecting the shadowroots of all elements.

E.g. the following will select the div elements in the first marker on a map card:

"ha-map $ ha-entity-marker $ div": |

But the following will select the div elements in all map markers on a map card (because we end the first key on the ha-entity-marker $ selector and start a new search within each result for div):

"ha-map $ ha-entity-marker $":
  "div": |

NOTE 2: Following on the note above; due to the high level of load order optimization used in Home Assistant, it is not guaranteed that the ha-entity-marker elements exist at the time when card-mod is looking for them. If you break the chain once more:

"ha-map $":
  "ha-entity-marker $":
    "div": |

then card-mod will be able to retry looking from the ha-map $ point at a later time, which may lead to more stable results.

In short; if things seem to be working intermittently - try splitting up the chain into several steps.

The DOM navigation can be tricky to get right the first few times, but you'll eventually get the hang of it.

To help you, you can use your browsers Element inspector to see which steps card-mod takes.

• Open up the element inspector and find the base element (e.g. #shadow-root or card contained by <hui-card> or <ha-card> contained by a custom card or other element. See README-application for more details.). This should contain a <card-mod> element whether you specified a style or not.
• Make sure the <card-mod> element is selected.
• Open up the browsers console (in chrome you can press Esc to open the console and inspector at the same time).
• Type in $0.card_mod_input and press enter.
  This is the style information that step of the chain was given. If this is a string, you're at the end of the chain. If it's an object, you can move on to the next step.
• Type in $0.card_mod_children and press enter.
  This is a set of any <card-mod> elements in the next step of any chain. Clicking "card-mod" in the value: of the set items will bring you to that <card-mod> element in the inspector, and you can keep on inspecting the rest of the chain.
• You can also use $0.card_mod_parent to find the parent of any <card-mod> element in a chain.

For a bit more information, you can use the following in the configuration of the card you're having problems with. It may or may not help you.

card_mod:
  debug: true

You can also set debug via theme variables. See README-themes.md

Cards that don't have a <ha-element> can still be styled by using the supplied custom:mod-card card.

This is only necessary in very very few instances, and likely to bring more problems than it solves.

Most likely your card contains another card, in which case that is the one you should apply the styles to.

Enough warnings.

type: custom:mod-card
card:
  type: custom:beloved-custom-card
  ...
card_mod:
  style: |
    ha-card {
      ...
    }

The mod-card will create a <ha-card> element and put your card inside that. If you wish to style the ha-card so that it is transparent, include the following style.

type: custom:mod-card
card:
  type: custom:beloved-custom-card
  ...
card_mod:
  style: |
    ha-card {
      background: none;
      box-shadow: none;
      border: none;
      transition: none;
    }

Rows in entities conditional rows can be styled directly. If you style the conditional config itself, you need to take care as the conditional row wrapper is not in a shadowRoot so styles may leak to other rows/elements.

type: entities
state_color: true
entities:
  - type: conditional
    conditions:
      - condition: state
        entity: input_boolean.test_boolean
        state: "off"
    row:
      entity: sun.sun
      name: Conditional Sun
      card_mod:
        style: |
          :host {
            color: red;
          }

Styling a conditional row config using shadowRoot. This method is available for legacy configurations.

type: entities
state_color: true
entities:
  - type: conditional
    conditions:
      - condition: state
        entity: input_boolean.test_boolean
        state: "on"
    row:
      entity: sun.sun
      name: Conditional Sun 
    card_mod:
      style:
        hui-simple-entity-row $ hui-generic-entity-row $: |
          .row {
            color: red;
          }

Styling a conditional config where styles will 'leak' to all rows.

type: entities
state_color: true
entities:
  - type: conditional
    conditions:
      - condition: state
        entity: input_boolean.test_boolean
        state: "on"
    row:
      entity: sun.sun
      name: Conditional Sun
    card_mod:
      style: |
        :host {
          --primary-text-color: red;
        }

The elements in a picture-elements conditional element can be styled directly. If you style the conditional config itself, you need to take care as the conditional element wrapper is not in a shadowRoot so styles may leak to other rows/elements.

type: picture-elements
image:
  media_content_id: https://demo.home-assistant.io/stub_config/t-shirt-promo.png
elements:
  - type: conditional
    conditions:
      - entity: input_boolean.test_boolean
        state: "on"
    elements:
      - type: state-badge
        entity: sun.sun
        style:
          left: 25%
          top: 25%
        card_mod:
          style: |
            :host {
              color: green;
            }

Styling the conditional config. This method is available for legacy configurations.

type: picture-elements
image:
  media_content_id: https://demo.home-assistant.io/stub_config/t-shirt-promo.png
elements:
  - type: conditional
    conditions:
      - entity: input_boolean.test_boolean
        state: "on"
    elements:
      - type: state-badge
        entity: sun.sun
        style:
          left: 25%
          top: 25%
    card_mod:
      style:
        hui-state-badge-element $ ha-state-label-badge $: |
          :host {
            color: red;
          }

Styling the conditional config where styles will 'leak' to all elements.

type: picture-elements
image:
  media_content_id: https://demo.home-assistant.io/stub_config/t-shirt-promo.png
elements:
  - type: conditional
    conditions:
      - entity: input_boolean.test_boolean
        state: "on"
    elements:
      - type: state-badge
        entity: sun.sun
        style:
          left: 25%
          top: 25%
    card_mod:
      style: |
        :host {
          --primary-text-color: purple;
        }

All my test cases are available in the test/views directory.

You can a demo in docker by going to the test directory and running:

docker-compose up

Then going to http://localhost:8125 and logging in with username dev and password dev.

Or you could use the vscode devcontainer and run the task "Run hass".

For details on where card-mod is applied see README-application.

For instructions on how to develop a card-mod theme, see README-themes.md.

For adding card-mods styling powers to your custom card, see README-developers.md.

If at any time you need to clear the Home Assistant Application cache, which is used in addition to Browser cache, starting with Version 4.2.0 you can use a custom action to clear the Home Assistant Application cache and reload the Browser. This can be very convenient especially for devices where the option is hidden in a debugging menu and will clear more than just the application cache (e.g. localStorage which clears out many stored items like Browser Mod Browser ID).

The action can be executed using fire-dom-event with key card_mod with action: clear_cache. This can be used on any card that supports the fire-dom-event action which includes all standard Home Assistant cards.

Example button to clear cache and reload.

show_name: true
show_icon: true
type: button
name: Clear Frontend Cache
tap_action:
  action: fire-dom-event
  card_mod:
    action: clear_cache