Typora allows to use <img> tag for displaying images, which can also be used to adjust the size of images.

For example, you could specify the width or height attribute of an <img> tag, or set the width/height in its style attribute:

<img src="https://www.google.com/doodles/kamma-rahbeks-241st-birthday" width="200px" />

<!--or-->


Another common use case is that when you try to insert a retina image, and want to scale it to a “correct” size according, then you could specify a zoom factor in its style attribute.
<img src="https://www.google.com/doodles/kamma-rahbeks-241st-birthday" style="zoom:50%" />

Above syntax can be understood and displayed by Typora. Although you could set other css properties in its style attribute, they will be ignored when you edit or preview by Typora, but could affect the exported HTML or PDF.