express (using multer) Error: Multipart: Boundary not found, request sent by POSTMAN

Question

Notice: only when I use form-data body form in Postman (which is the form I have to use because I want to send files beside text fields), I get:

Error: Multipart: Boundary not found.

when I use x-www-form-urlencoded everything is ok. (ofcourse when body-parser is used as middleware)

This is Request Content: (made by Postman)

POST /test HTTP/1.1
Host: localhost:3000
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW
Cache-Control: no-cache
Postman-Token: 61089a44-0b87-0530-ca03-a24374786bd1

------WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name="test"

a simple word
------WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name="data"

good
------WebKitFormBoundary7MA4YWxkTrZu0gW--

index.js:

var express = require('express');
var app = express();

var multer = require('multer');
var upload = multer();

app.post('/test', upload.array(), function (req, res, next) {
    console.log(req.body.test);
    console.log(req.body);
});

app.listen(3000, function () {
    console.log('app started');
});

if you are having this issue in react native check this answer [enter link description here](https://stackoverflow.com/a/71205192/13989650) — Shazil Sattar, Feb 21 '22 at 11:15

score 131 · Accepted Answer · edited May 11 '20 at 22:32

131

I found the solution. I only had to prevent Postman to send a Content-Type header. So I just removed it from request headers.

edited May 11 '20 at 22:32

Kalle Richter

8,008
26
77
177

answered Apr 06 '18 at 13:38

5

Thank you it works. Can you explain the reason behind this? – Hassam Saeed Dec 07 '20 at 11:22
@HassamSaeed https://stackoverflow.com/a/67996268/13328625 I think this answer answers the question – InvalidHop Mar 14 '23 at 06:01

score 11 · Answer 2 · answered Aug 14 '21 at 07:12

To give some insight on why that is happening,

When using content type multipart/form-data in any HTTP request, you can add a boundary information alongside the Content-Type specification like:

Content-Type: multipart/form-data; boundary=MyBoundary

You can replace MyBoundary with any string of your liking.

Then you will have to encode your form data (name=Abebe&age=5) as:

--MyBoundary
Content-Disposition: form-data; name="name"

Abebe
--MyBoundary
Content-Disposition: form-data; name="age"

5
--MyBoundary--

For more info read this StackOverflow question and answer

score 6 · Answer 3 · answered Aug 07 '22 at 08:12

If you are using fetch method

fetch("http://localhost:4000/upload_files", {
    method: 'POST',
    body: formData,
    headers: {
      "Content-Type": "multipart/form-data"
    }
})

headers so that Fetch api automatically set the headers. Now remove headers or "Content-Type": "multipart/form-data"

fetch("http://localhost:4000/upload_files", {
    method: 'POST',
    body: formData
})

Now it works

score 5 · Answer 4 · answered Mar 24 '20 at 10:16

5

For JMeter and postman remove Content-Type from header.

it will resolve your issue.

answered Mar 24 '20 at 10:16

SANKET GIRME

67
1
2

score 3 · Answer 5 · answered Jun 07 '20 at 13:07

I am going to expand a little bit on user9150719 for those who are having the same issue with the frontend side of things and are wondering where to remove the headers.

I had the same issue; I was trying to post from an Angular app to my Nodejs server. my post request included raw data and a file input. So I was thinking FormData()

Angular Service

//Declare header variables. 

formDataHeader = {
        headers: new HttpHeaders({
          Accept: 'application/json',
          'Access-Control-Allow-Origin': '*',
          'Content-Type': 'multipart/form-data',
          Authorization: 'Bearer ' + this._myService.getToken()
        })
      };

//Post function to Nodejs server
    addNewContact(contact: FormData): any {

        return this._httpClient.post(
          environment.apiBaseUrl + '/contacts', // POST /api/contacts
          (contact), // contact data,
          this.formDataHeader
        );
    }

My formData was setup properly. I was able to get all the data, but the problem is that I had setup couple headers in my request that resulted in what user9150719 was experiencing.

My solution was to simplify my headers to this:

formDataHeader = {
        headers: new HttpHeaders({
          Authorization: 'Bearer ' + this._myService.getToken()
        })
      };

Another important thing to point out is that I didn't need to set the enctype="multipart/form-data" on my <form></form> tag.

Even though I had an httpInterceptor setup (I don't think it is working properly), I still needed to add the Authorization header on all my requests, but all other headers were resulting in my api call to return unexpected results.

Finally I think (but I am not entirely sure) that the reason why I didn't need to setup extra headers, is because in my NodeJS server, I already configured what headers to expect.

Node.JS Server

// app.js

app.use('/public/uploads', express.static('uploads'));
app.use('/public', express.static('public'));
app.use(express.static(path.join(__dirname, 'public')));
app.use(cors());
app.use((req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*');
    res.header('Access-Control-Allow-Headers', 'x-www-form-urlencoded, Origin, X-Requested-With, Content-Type, Accept, Authorization, *');
    if (req.method === 'OPTIONS'){
        res.header('Access-Control-Allow-Methods', 'GET, PUT, POST, PATCH, DELETE, OPTIONS');
        res.setHeader('Access-Control-Allow-Credentials', true);
        return res.status(200).json({});
    }
    next();
});
app.use(bodyParser.urlencoded({limit: '50mb', extended: true}));
app.use(bodyParser.json({limit: '50mb', extended: true}));

So I think that if your server is setup to handle certain types of headers (Content-Type, Authorization, Origin, etc.), You don't necessarily need to set those headers again on your frontend when you send your request to the server. There are certain exceptions, such Authorization which in certain cases need to be set; probably because they carry some data in the form of token or something in that regards.

I hope this helps someone out there!

score 0 · Answer 6 · answered Aug 26 '22 at 04:06

Don't mention CONTENT-TYPE header while uploading files from FE using axios/fetch or anything 3rd HTTP handler.

Reason bcoz we don't know the boundary of our files. If you pass only 'multipart/form-data' as Content-Type, you will get an error since we aren't passing boundary in there.

So, let the browser add it (multipart/form-data) along with Boundary based on the files attached.

AND if you want to send some data along with files, you should be sending them as a multipart/form-data(Again we don't need to add this header manually) type only.
We CANNOT send multiple Content-Type data at once for any http call. Please refer below code.

async onUpload(){
  const formData=new FormData();
  formData.append('files', file1);
  formData.append('files', file2);
  formData.append('data', {key1:value1, key2:value2});
  const res=await axios.post(URL, formData);
}

FYI @hassam-saeed

wuahi · Answer 7 · 2022-09-06T08:08:13.327

Just if someone has the same issue i had.

NestJs - BackEnd

NextJs - FrontEnd

I was trying to do something like:

const formData = new FormData()

formData.append('context', body.context.toString())
    
body.files.map((file) => {
    formData.append('files', file, `${file.name}`)
})

const response = await fetch(url, {
    method: 'POST',
    headers: {
        'Content-Type': 'multipart/form-data',
        ...(access_token ? { Authorization: `Bearer ${access_token}` } : {}),
    },
    body: formData,
})

But because this 'Content-Type' overrides the browsers setting of 'Content-Type' AND the content-length is not explicitly set (which was the real issue i think) ,the form-data was showing up on the backend still encoded. So NestJS was not able to parse the 'context' variable or the 'files'.

Also, if you use api routes in NextJS, remeber to check that no-where in there is the 'Content-Type' overridden.... I also had this issue.

score 0 · Answer 8 · answered Oct 05 '22 at 07:45

0

I did this instead

const form = new FormData();
headers['Content-Type'] = `multipart/form-data; boundary=${form._boundary}`;

Source: https://stackoverflow.com/a/54796556/8590519

answered Oct 05 '22 at 07:45

Aeriel

65
6

express (using multer) Error: Multipart: Boundary not found, request sent by POSTMAN

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