The matSort and mat-sort-header are used, respectively, to add sorting state and display to tabular data.

Adding sort to table headers

To add sorting behavior and styling to a set of table headers, add the <mat-sort-header> component to each header and provide an id that will identify it. These headers should be contained within a parent element with the matSort directive, which will emit a matSortChange event when the user triggers sorting on the header.

Users can trigger the sort header through a mouse click or keyboard action. When this happens, the matSort will emit a matSortChange event that contains the ID of the header triggered and the direction to sort (asc or desc).

Changing the sort order

By default, a sort header starts its sorting at asc and then desc. Triggering the sort header after desc will remove sorting.

To reverse the sort order for all headers, set the matSortStart to desc on the matSort directive. To reverse the order only for a specific header, set the start input only on the header instead.

To prevent the user from clearing the sort state from an already sorted column, set matSortDisableClear to true on the matSort to affect all headers, or set disableClear to true on a specific header.

Disabling sorting

If you want to prevent the user from changing the sorting order of any column, you can use the matSortDisabled binding on the mat-sort, or the disabled on a single mat-sort-header.

Using sort with the mat-table

When used on a mat-table header, it is not required to set a mat-sort-header id on because by default it will use the id of the column.

Accessibility

When you apply MatSortHeader to a header cell element, the component wraps the content of the header cell inside a button. The text content of the header cell then becomes the accessible label for the sort button. However, the header cell text typically describes the column and does not indicate that interacting with the control performs a sorting action. To clearly communicate that the header performs sorting, always use the sortActionDescription input to provide a description for the button element, such as "Sort by last name".

MatSortHeader applies the aria-sort attribute to communicate the active sort state to assistive technology. However, most screen readers do not announce changes to the value of aria-sort, meaning that screen reader users do not receive feedback that sorting occurred. To remedy this, use the matSortChange event on the MatSort directive to announce state updates with the LiveAnnouncer service from @angular/cdk/a11y.

If your application contains many tables and sort headers, consider creating a custom directives to consistently apply sortActionDescription and announce sort state changes.