---
title: "ResizeObserverSize | JavaScript maps SDK"
description: "Documentation for MapTiler SDK"
---

> For AI agents: a documentation index is available at [/llms.txt](https://docs.maptiler.com/llms.txt). Markdown versions of all pages are available by appending .md to any URL.

# Interface ResizeObserverSize

The **`ResizeObserverSize`** interface of the Resize Observer API is used by the ResizeObserverEntry interface to access the box sizing properties of the element being observed.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/ResizeObserverSize)

interface ResizeObserverSize {  
    [blockSize](#blocksize): number;  
    [inlineSize](#inlinesize): number;  
}

##### Index

### Properties[](#properties)

[blockSize](#blocksize) [inlineSize](#inlinesize)

## Properties[](#properties-1)

### `Readonly`blockSize[](#blocksize)

blockSize: number

The **`blockSize`** read-only property of the ResizeObserverSize interface returns the length of the observed element's border box in the block dimension. For boxes with a horizontal writing-mode, this is the vertical dimension, or height; if the writing-mode is vertical, this is the horizontal dimension, or width.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/ResizeObserverSize/blockSize)

### `Readonly`inlineSize[](#inlinesize)

inlineSize: number

The **`inlineSize`** read-only property of the ResizeObserverSize interface returns the length of the observed element's border box in the inline dimension. For boxes with a horizontal writing-mode, this is the horizontal dimension, or width; if the writing-mode is vertical, this is the vertical dimension, or height.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/ResizeObserverSize/inlineSize)