Hi @Davide - While this might not be possible with a custom integration action, you might want to consider the following options:

• Build a zap that saves the file to the user’s Dropbox (or Google Drive etc..) folder that’s automatically syncing with their computer.
• Build a zap that sends them the download link in an email or in a Slack message.

Actually I need only something like opening an URL in a new browser tab, with a string like this  in address bar:

https://www.app.fattura24.com/api/v0.3/GetFile?apiKey=xxxx&docId=123456

any suggestion?

@Davide The problem here is that Zapier doesn’t work in Request-Response fashion so you can’t actually respond to HTTP requests with a custom response.

At last I solved by adding two steps in my Zap:

1. Zapier webhooks to post my request;
2. Email by Zapier to send the result of the previous step as attachment

Thank you very much for your support

@ikbelkirasan 
Now I’d like to build my GetFile action in a way that its result looks like the result I get by using Webhooks, that is the object ‘File’ ?

I tried to add this in my scripting:

 // Action 'Get File'
    get_file_pre_write: function(bundle)
    {
     var pjson = require('package.json');
     var fields = bundle.action_fields_full;
     var keys = Object.keys(fields);
     var docId = fields docId];
     var apiKey = bundle.request.params.apiKey;

     bundle.request.params =
     {
         apiKey: apiKey,
         docId: docId,
         source: 'F24-Zap ' + pjson.version
     };
     return bundle.request

    },

    get_file_post_write: function(bundle)
    {
       return bundle.response;
    },

When I test this code as a result I don’t get the File

@Davide Unfortunately, I haven’t built app in the Legacy Web Builder. However, it might be useful to look at this example app: https://github.com/zapier/zapier-platform/blob/master/example-apps/files/triggers/newFile.js