Why is response.data an html string instead of json object? node.js, express.js, react

My app was running perfectly fine on the localhost, but once I deployed to Heroku I got this bug:

When I console.log(response.data) in the client side I receive this string instead of the res.json with my user info:

“<!doctype html><html lang=”en”><meta charset=”utf-8″/><link rel=”icon” href=”/climbing.png”/><meta name=”viewport” content=”width=device-width,initial-scale=1″/><meta name=”theme-color” content=”#000000″/><meta name=”description” content=”Web site created using create-react-app”/><link rel=”apple-touch-icon” href=”/logo192.png”/><link rel=”manifest” href=”/manifest.json”/>Climber Nation<script defer=”defer” src=”/static/js/main.56943839.js”><link href=”/static/css/main.a3875cba.css” rel=”stylesheet”>You need to enable JavaScript to run this app.<div id=”root”>”

    headers: {
      "Content-Type": "application/json",
      "Access-Control-Allow-Origin": "*",
    credentials: true,
    origin: ["https://climber-nation.herokuapp.com/"],
    methods: ["GET", "POST"],

const authenticateToken = (req, res, next) => {
  try {
    const token = req.headers["authorization"];

    if (token == null) {
      return res.sendStatus(401);
    } else {
      jwt.verify(token, process.env.ACCESS_TOKEN_SECRET, (error, decoded) => {
        if (error) {
          return res.sendStatus(403);
        } else {
          req.user = decoded;

          return next();
  } catch (error) {
    return res.status(400).json({ error: error });


app.get("/authentication", authenticateToken, async (req, res) => {
  const username = req.user.username;

  const allUserInfo = await db("users").select("*").where("username", username);

  const image = await db("images")
    .innerJoin("users", "images.image_id", "users.user_id")
    .where("username", username);

  const imageFile =
    "https://climber-nation.herokuapp.com/images/" + image[0]?.filename;

    allUserInfo: allUserInfo[0],
    imageFile: imageFile,


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Method 1

A friend helped me to solve.

I had these lines of code in my server, but had a small typo and also needed to rearrange the locations they were in.

Beggining of server app:
app.use(express.static(path.join(__dirname, "build")));

End of server app:

app.get("*", (req, res) => {
  res.sendFile(path.join(__dirname, "build", "index.html"));

My deployed app is now fully working.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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