nodejs special characters encoding issue only when hosted in IIS with iisnode module

Question

using express and body-parser with the following setup:

const express = require('express');
const bodyParser = require('body-parser');
const app = express();

app.use(bodyParser.json({limit: '100mb', extended: true,type: 'application/*+json;charset=utf-8'}))
app.use(bodyParser.urlencoded({limit: '100mb', extended: true}));
app.use(bodyParser.text({defaultCharset: 'utf-8'}));
app.use(express.json());

When running the nodejs server using npm start, special characters inside the json body are utf-8 encoded as expected. Once hosted in IIS, the character encoding fails. Only difference is the hosting environment. The .NET Globalization options are set correctly for the IIS site hosting the nodejs server application with 'utf-8' settings, without making any difference. Double-checked web.config. What could possibly be messing up the incoming requests data?

json body request output - when nodejs is hosted in IIS

json body request output - when server is run directly using npm start:

A hint on what may be going on: https://www.i18nqa.com/debug/bug-utf-8-latin1.html

Anyone know where to look?

Answer 1

Found the issue, which is probably as simple as it is stupid. I will post it anyway since I spent a lot of time looking in the wrong places. The problem was divided. The baretail app used for reviewing the logged request on the server was run with an ANSI charset. Changing it to UTF-8 displayed the special characters correctly on screen. The API to further receive this request saved the special characters as "unknown characters" - leading me to start looking at the problem already on what were coming in on the nodejs server.

Absolutely worth noting - The API to further receive this request is the Facebook Conversions API -> https://developers.facebook.com/docs/marketing-api/conversions-api/using-the-api#verify. It does not handle the requests as 'application/json' but 'application/x-www-form-urlencoded' with a form-data request containing the json object along with the facebook param "format" set to "json". Content-Type "application/json" works technically for this API-call but special characters are saved with the "unknown char question mark" symbol. Setting the "Accept-Language" in header or the facebook "locale" param in the request does not work for this API-call specifically.