ShareX

You can set Kutt as your default URL shortener in ShareX app.

You need to get your API key from the settings page in Kutt. Replace your API key with yourapikeyhere and copy the code:

{
  "Name": "kutt",
  "DestinationType": "URLShortener",
  "RequestURL": "https://kutt.it/api/url/sharex",
  "Headers": {
    "X-API-Key": "yourapikeyhere",
    "Target": "{\"target\":\"$input$\"}"
  },
  "URL": "$json:shortUrl$"
}

Now open ShareX app, go to Destinations > Destination settings..., open the last option "Custom Uploaders". On this page find import button and select "import from clipboard". (You can also save the file in a .json file and import from file)

Now in destinations menu choose "Custom URL Shortener" as the default shortener.