How do I resize my video to 9:16 aspect ratio?

Shotstack API
1

I want video show my video vertically in an aspect ratio of 9:16. Right now it shows horizontally.

2

You just need to set the output aspect ratio using the aspectRatio parameter.

The JSON would look like as follows:

"output": {
   "format": "mp4",
   "resolution": "sd",
   "aspectRatio": "9:16"
}

Full JSON below:

{
    "timeline": {
        "soundtrack": {
            "src": "https://s3-ap-southeast-2.amazonaws.com/shotstack-assets/private/epic.mp3"
        },
        "background": "#000000",
        "tracks": [
            {
                "clips": [
                    {
                        "asset": {
                            "type": "html",
                            "html": "<b>Horizontal Videos for Social Media</b>",
                            "css": "b { font-family: \"Open Sans\"; color: #ffffff; font-size: 24px; text-align: left; }",
                            "width": 400,
                            "height": 200,
                            "background": "transparent"
                        },
                        "start": 1.2,
                        "length": 5,
                        "position": "bottomLeft",
                        "offset": {
                        	"x": 0.05,
                        	"y": 0.05
                        },
                        "transition": {
                            "in": "fade",
                            "out": "fade"
                        }
                    }
                ]
            },
            {
                "clips": [
                    {
                        "asset": {
                            "type": "video",
                            "src": "https://shotstack-assets.s3.ap-southeast-2.amazonaws.com/footage/hot-air-balloon-vertical.mp4",
                            "trim": 5
                        },
                        "start": 1,
                        "length": 6,
                        "transition": {
                            "in": "fade",
                            "out": "fade"
                        },
                        "fit": "contain"
                    }
                ]
            }
        ]
    },
    "output": {
        "format": "mp4",
        "resolution": "hd",
        "aspectRatio": "9:16"
    }
}

Or with PHP you should be able to use ->setAspectRatio("9:16").

API reference doc is here: https://shotstack.io/docs/api