Sending an arbitrary long array of files in an HTTP request node

Questions
,
1

Describe the problem/error/question

I need to execute an HTTP request where the server expects me to provide multiple files under the same filed data. The number of files is not static so I cannot just map every file to a field in the n8n node. Is that even possible via the http node or should I use a code node?

What is the error message (if any)?

I tried it like this but obviously if I have more than 1 file I get an error that the binary with id , doesn’t exist.

Please share your workflow

Information on your n8n setup

  • n8n version: 2.21.7
  • Database (default: SQLite): postgres
  • n8n EXECUTIONS_PROCESS setting (default: own, main): own
  • Running n8n via (Docker, npm, n8n cloud, desktop app): docker
  • Operating system: macOS
2

Hi @Vidomina

Try this

  1. Copy the JSON block above.
  2. Open your n8n editor.
  3. Press Ctrl+V (or Cmd+V on Mac) to paste the nodes directly into the canvas.
  4. To test: Click “Execute Workflow”.
  5. To use with your real data:
    • Delete the “Mock Data Generator” node.
    • Connect your actual data node to the “Construct Multipart Body” node.
    • Ensure your data node provides binary files (the code will automatically find all binary keys, excluding any key named params).
3

Hello @kjooleng thanks for the suggestion!

I ran into 2 issues: first your Construct Multipart Body works well for text but files like pdf and docx get absolutely muffled by the approach.

I modified it to:

the second is that when I feed the request to the service now I get a:
Content-Type is not supported

I haven’t gotten to debugging that yet.

4

Here is the modified json

This allows you to verify that the logic works for both metadata (JSON) and binary content (simulating your PDFs/Docs) without needing your actual files present.

5

Thanks for the edited mock data generator.
I looked into why the service was returning
Content-Type is not supported and it looks like the HTTP node doesn’t send anything.

I tried setting it to n8n-binary + filed name multipartBody but I got an error " source.on is not a function" - I probably have messed up something with the javascript as I am not very experienced with n8n’s functions. I’ll dig around the documentation and try and figure it out but if I’m missing something obvious any input is welcome.

6

Use this specific Code Node and these exact HTTP Request settings

return (async () => {
  const CRLF = '\r\n';
  const items = $input.all();
  const result = [];

  for (let i = 0; i < items.length; i++) {
    const item = items[i];
    // 1. Create a unique boundary
    const boundary = `----n8nboundary${Math.random().toString(36).slice(2, 11)}`;
    const chunks = [];

    const pushText = (text) => chunks.push(Buffer.from(text, 'utf8'));

    // 2. ADD THE 'aggregate' FIELD MANUALLY
    // Since we are in 'Binary' mode, this MUST be in the buffer
    pushText(`--${boundary}${CRLF}`);
    pushText(`Content-Disposition: form-data; name="aggregate"${CRLF}`);
    pushText(`${CRLF}true${CRLF}`);

    // 3. Handle 'params' file
    if (item.binary?.params) {
      const paramsMeta = item.binary.params;
      const paramsBuf = await this.helpers.getBinaryDataBuffer(i, 'params');
      const fileName = paramsMeta.fileName || 'params.json';
      const mimeType = paramsMeta.mimeType || 'application/json';

      pushText(`--${boundary}${CRLF}`);
      pushText(`Content-Disposition: form-data; name="params"; filename="${fileName}"${CRLF}`);
      pushText(`Content-Type: ${mimeType}${CRLF}${CRLF}`);
      chunks.push(paramsBuf);
      pushText(CRLF);
    }

    // 4. Handle all other files (mapped to 'data')
    if (item.binary) {
      const dataKeys = Object.keys(item.binary).filter((k) => k !== 'params');
      for (const key of dataKeys) {
        const fileMeta = item.binary[key];
        const fileBuf = await this.helpers.getBinaryDataBuffer(i, key);
        const fileName = fileMeta.fileName || key;
        const mimeType = fileMeta.mimeType || 'application/octet-stream';

        pushText(`--${boundary}${CRLF}`);
        pushText(`Content-Disposition: form-data; name="data"; filename="${fileName}"${CRLF}`);
        pushText(`Content-Type: ${mimeType}${CRLF}${CRLF}`);
        chunks.push(fileBuf);
        pushText(CRLF);
      }
    }

    // 5. Close boundary
    pushText(`--${boundary}--${CRLF}`);

    const body = Buffer.concat(chunks);
    
    // The exact header the server needs to see
    const contentTypeHeader = `multipart/form-data; boundary=${boundary}`;

    result.push({
      json: item.json,
      binary: {
        multipartBody: await this.helpers.prepareBinaryData(
          body,
          'request.bin',
          contentTypeHeader
        ),
      },
    });
  }

  return result;
})();

Do not add anything to “Body Parameters”. Configure http request like this:

  • Method: POST
  • URL: your-api-endpoint
  • Send Body: true
  • Body Content Type: Binary ← This is the most important part
  • Input Data Field Name: multipartBody
  • Options: (Leave empty)

image
image1394×833 19.1 KB

7

What version of n8n are using. I tried couple and I was only able to get it going consistently on
1.123.65. Sadly when I was able to run it n8n actually tried to upload the body sending every single bit as its own form-data:

Host: javeRequestCatcher.127.0.0.1.nip.io
Accept: application/json,text/html,application/xhtml+xml,application/xml,text/*;q=0.9, image/*;q=0.8, */*;q=0.7
Accept-Encoding: gzip, compress, deflate, br
Connection: close
Content-Length: 69898
Content-Type: multipart/form-data; boundary=--------------------------6c56103870e43e66b91b529d
User-Agent: axios/1.18.0

----------------------------6c56103870e43e66b91b529d
Content-Disposition: form-data; name="0"

45
----------------------------6c56103870e43e66b91b529d
Content-Disposition: form-data; name="1"

45
 
<skip a lot of lines>

13
----------------------------6c56103870e43e66b91b529d
Content-Disposition: form-data; name="668"

10
----------------------------6c56103870e43e66b91b529d--

On I wanna say every 2.xx version I tried I just got source.on is not a function as an error

8

Will this help?

  1. Delete the HTTP Request node.

  2. Put this code in a Code Node​.

const axios = require('axios');
const FormData = require('form-data');

const item = $input.first();
const form = new FormData();

// 1. Add 'aggregate'
form.append('aggregate', 'true');

// 2. Add 'params'
if (item.binary?.params) {
  const buf = await this.helpers.getBinaryDataBuffer(0, 'params');
  form.append('params', buf, { filename: 'params.json', contentType: 'application/json' });
}

// 3. Add all other files to 'data'
if (item.binary) {
  const keys = Object.keys(item.binary).filter(k => k !== 'params');
  for (const key of keys) {
    const buf = await this.helpers.getBinaryDataBuffer(0, key);
    const file = item.binary[key];
    form.append('data', buf, { filename: file.fileName || key, contentType: file.mimeType });
  }
}

// 4. Execute request directly
try {
  const response = await axios.post('http://example.org/project/tag', form, {
    headers: form.getHeaders(),
  });
  return { json: response.data };
} catch (error) {
  return { json: { error: error.message } };
}
  1. Go to your Settings (or Environment variables) and ensure that NODE_FUNCTION_ALLOW_EXTERNAL includes axios and form-data if your specific instance restricts them (though they are usually bundled). If it’s n8n Cloud or standard Docker, axios is built-in.
9

That worked great until the second the endpoint required authentication - custom code nodes do not have permissions to work with saved credentials.

After a bunch brainstorming I ended up creating a custom node. Currently the implementation is quick and dirty, but if ever have time I’ll get it up to standard and post it as a community node.

10

Thanks for this