# The filters block

The filters block contains information on how the layer is being filtered before displaying. In order for a feature to be shown on the map it must evaluate the filter expression to `true`.

Filters are written using a JSON infix notation that looks like one of `[identifier, operator, operand]`, `true` or `false` .

* Valid identifiers are either a feature property or a nested expression.
* Valid operators are:
  * `"lt"` – Less than
  * `"gt"` – Greater than
  * `"le"` – Less than or equal to
  * `"ge"` – Greater than or equal to
  * `"eq"` – Equal to
  * `"ne"` – Not equal to
  * `"and"` – And, cast to boolean
  * `"or"` – Or, cast to boolean
  * `"cn"` – Contains the operand, cast to string
  * `"nc"` – Does not contain the operand, cast to string
  * `"in"` – Contained in the operand list
  * `"ni"` – Not contained in the operand list
  * `"is"` – Used to match against null values
  * `"isnt"` – Used to match against null values
* Operands are:
  * A numerical value, a string value, a boolean value
  * An array of numerical, string, or boolean values, a shorthand expanded to these patterns:
    * Input 1: `[id, "in", [element1, …, elementN]`
    * Expansion 1: `id` is equal (`”eq”`) to one of more of the elements
    * Input 2: `[id, "ni", [element1, …, elementN]`
    * Expansion 2: `id` is not equal (`”ne”`) to any of the elements
    * Not defined for operators other than `"in"` and `"ni"`
  * A nested expression
* In cases of type mismatch cast the identifier value to the operand’s type
  * Type casting applies element-wise to lists with `"in"` and `"ni"` operators

{% code title="Example of a filter block that filters out features with a value less than 50000 on the “acres” property" %}

```jsx
"filters": ["acres", "lt", 50000]
```

{% endcode %}

{% code title="Example of a more complex filter block" %}

```jsx
"filters": [["acres", "ge", 50000], "and", ["acres", "le", 70000]]
```

{% endcode %}