# Dimension matchers

Dimension Selectors allow you to identify and filter UI elements based on their physical size on the screen. 

### **Overview**

| **Selector** | **Description**                                                                             |
| ------------ | ------------------------------------------------------------------------------------------- |
| `width`      | Targets an element with a specific width in pixels.                                         |
| `height`     | Targets an element with a specific height in pixels.                                        |
| `tolerance`  | A value used to allow for minor rendering or rounding differences when matching dimensions. |

{% hint style="success" %}

#### Usage tips

* **Combine with Traits**: Use `tolerance` alongside `traits: square` if you need to find an element that is square but you only know its approximate size.
* **Device Variability**: Be careful with hardcoded pixel values when running tests on a wide variety of device models with different screen resolutions. Using a higher `tolerance` can help maintain cross-device compatibility.
  {% endhint %}

### `width` and `height`

These selectors match the exact pixel dimensions of an element as reported by the accessibility tree. Because screen densities vary across different devices (e.g., iPhone 15 vs. Pixel 7), it is recommended to combine `width` and `height` with other Selectors.

```yaml
# Taps a button that is exactly 200px wide
- tapOn:
    id: action_button
    width: 200

# Asserts that the profile header has a height of 350px
- assertVisible:
    id: profile_header
    height: 350
```

### `tolerance`

Rendering engines and screen scaling can result in slight variations in reported dimensions (e.g., a 100px button reporting as 99px or 101px). The `tolerance` parameter allows you to define a buffer range to ensure your tests remain stable across different devices.

If you set a `tolerance: 5`, Maestro will match any element within +/- 5 pixels of the target dimension.

```yaml
# Matches an icon that is 48px square, with a 2px wiggle room
- assertVisible:
    id: settings_icon
    width: 48
    height: 48
    tolerance: 2
```