Incorrect MIME Type when reading file using “Read/Write Files from Disk” node

[Mohamed3nan]

Bug Description

Hello,,

After updating n8n to the beta version, the Read/Write Files from Disk node returns a different MIME type than in the previous version (1.120.3).

In the previous version, an MP4 file written using the same node would later be read with the MIME type: video/mp4

After upgrading, reading the exact same MP4 file now returns: application/mp4

To Reproduce

1. Create a workflow that writes a .mp4 file using the Read/Write Files from Disk node.
2. Read the same .mp4 file using the same node.
3. Inspect the binary metadata returned.

Workflow to Reproduce:

{
  "nodes": [
    {
      "parameters": {
        "operation": "write",
        "fileName": "/n8n_data/output.mp4",
        "dataPropertyName": "data0",
        "options": {}
      },
      "type": "n8n-nodes-base.readWriteFile",
      "typeVersion": 1,
      "position": [
        656,
        208
      ],
      "id": "1786827e-1a17-4273-8c14-c0f6480e06a2",
      "name": "Read/Write Files from Disk1"
    },
    {
      "parameters": {
        "options": {
          "allowFileUploads": true
        }
      },
      "type": "@n8n/n8n-nodes-langchain.chatTrigger",
      "typeVersion": 1.4,
      "position": [
        432,
        208
      ],
      "id": "c6548e10-5d69-4019-9ae4-542003e532f3",
      "name": "When chat message received",
      "webhookId": "b473a745-8d04-4d83-bb7d-79a07edf99b2"
    },
    {
      "parameters": {
        "fileSelector": "/n8n_data/output.mp4",
        "options": {}
      },
      "type": "n8n-nodes-base.readWriteFile",
      "typeVersion": 1,
      "position": [
        912,
        208
      ],
      "id": "f2d42429-4a62-4d0a-bdbb-5aec3ee5526a",
      "name": "Read/Write Files from Disk"
    }
  ],
  "connections": {
    "Read/Write Files from Disk1": {
      "main": [
        [
          {
            "node": "Read/Write Files from Disk",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "When chat message received": {
      "main": [
        [
          {
            "node": "Read/Write Files from Disk1",
            "type": "main",
            "index": 0
          }
        ]
      ]
    }
  },
  "pinData": {
    "Read/Write Files from Disk1": [
      {
        "sessionId": "372fba937523464085366d881565fd29",
        "action": "sendMessage",
        "chatInput": "ee",
        "files": [
          {
            "fileName": "output.mp4",
            "fileSize": "805267 bytes",
            "fileExtension": "mp4",
            "fileType": "video",
            "mimeType": "video/mp4"
          }
        ],
        "fileName": "/n8n_data/output.mp4"
      }
    ],
    "When chat message received": [
      {
        "sessionId": "372fba937523464085366d881565fd29",
        "action": "sendMessage",
        "chatInput": "ee",
        "files": [
          {
            "fileName": "output.mp4",
            "fileSize": "805267 bytes",
            "fileExtension": "mp4",
            "fileType": "video",
            "mimeType": "video/mp4"
          }
        ]
      }
    ],
    "Read/Write Files from Disk": [
      {
        "mimeType": "application/mp4",
        "fileName": "output.mp4",
        "fileExtension": "mp4",
        "fileSize": "805 kB"
      }
    ]
  },
  "meta": {
    "templateCredsSetupCompleted": true,
    "instanceId": "4ae195bf9aee1a545632cb1a7b5f0d73fa1ec648553b781b97113639d10a41bf"
  }
}

Expected behavior

The node should preserve or correctly detect the MIME type and continue to return: video/mp4 instead of: application/mp4

Debug Info

Debug info

core

• n8nVersion: 1.121.0
• platform: docker (self-hosted)
• nodeJsVersion: 22.21.0
• nodeEnv: production
• database: postgres
• executionMode: regular
• concurrency: -1
• license: enterprise (production)
• consumerId: c7e31770-5ee2-46d8-a026-527286c836c1

storage

• success: all
• error: all
• progress: false
• manual: true
• binaryMode: memory

pruning

• enabled: true
• maxAge: 336 hours
• maxCount: 10000 executions

client

• userAgent: mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/142.0.0.0 safari/537.36
• isTouchDevice: false

Generated at: 2025-11-18T15:18:23.035Z

Operating System

Ubuntu

n8n Version

1.121.0

Node.js Version

22.21.0

Database

PostgreSQL

Execution mode

main (default)

Hosting

self hosted

[n8n-assistant]

Hey @Mohamed3nan,

Thank you for reaching out! We’ve received your issue and are looking into it. To help us track this internally, we’ve created a Linear ticket with the reference: "GHC-5546".

We’ll keep you updated as we make progress, but if you have any additional details or context to share, feel free to add them here - it’s always helpful!

Thanks for your patience and for bringing this to our attention.

---

For INTERNAL use only: GHC-5546

[MookieLian]

Thank you for raising this issue, the first step of triage is completed, and it has been routed internally for further investigation.

-> View Reproduction Workflow JSON

GET request to public sample endpoint for a temporary MP4 file

Write file to disk using a temporary directory path tmp(container specific). MIME type is video/mp4.

Read file from disk using the same path/name pointing the sample file has returned MIME type application/mp4.

Reproduction: Docker, Self-Host, Debian, Version: Next
#triage:complete

[andkit01]

If you connect the YouTube Upload node after the Read Binary File node, even if you specify MIME type as "video/mp4" on the Read Binary File node, and it says "video/mp4" on the output; the YouTube Upload node throws an error saying "Bad request - please check your parameters. Media type 'application/mp4' is not supported."

Does the MIME type issue only apply to the Read Binary File node, or also the YouTube Upload node?

Thanks

[tderouze]

Hello,

I am facing exactly the same issue. Some additional comment :

• it occurs since the last upgrade of n8n (the workflow was working fine before)
• file --mime-type -b "myvideo.mp4" on the lxc returns mimetype vidéo/mp4
• adding this code fix the mimetype output, but the vidéo wrongly upload to youtube (but the workflow indivates success)

{
  "nodes": [
    {
      "parameters": {
        "jsCode": "// Récupère le premier item avec binary data\nconst item = $input.first();\n\nif (!item.binary || !item.binary.data) {\n  throw new Error('Pas de données binaires trouvées');\n}\n\n// Récupère les données binaires ORIGINALES (Buffer)\nconst originalBinary = $input.first().binary.data;\n\n// Crée une NOUVELLE entrée binaire avec MIME type corrigé\nconst newBinaryData = {\n  data: originalBinary.data,  // Buffer original (CRUCIAL)\n  mimeType: 'video/mp4',      // ✅ CORRECTION ICI\n  fileName: originalBinary.fileName || 'Saint_Andre.mp4',\n  fileExtension: 'mp4',\n  fileSize: originalBinary.fileSize\n};\n\nreturn [{\n  json: {\n    originalMime: originalBinary.mimeType,\n    newMime: 'video/mp4',\n    fileSize: originalBinary.fileSize\n  },\n  binary: {\n    data: newBinaryData   // NOUVEAU champ binaire avec mimeType correct\n  }\n}];\n"
      },
      "type": "n8n-nodes-base.code",
      "typeVersion": 2,
      "position": [
        1120,
        -448
      ],
      "id": "83bfa044-a781-4be4-88ad-46e8434b1718",
      "name": "Code in JavaScript"
    }
  ],
  "connections": {
    "Code in JavaScript": {
      "main": [
        []
      ]
    }
  },
  "pinData": {},
  "meta": {
    "instanceId": "89af474e60c70a1e45bf242e266e9ca1446dd974ab86f6d185b8ccded3effed2"
  }
}

[GaloranM]

Hi, is this a bug that will get fixed or just a new method? sending this because i’m running into the same issue with mp4 uploads since last update.

[fvaswani]

No official response from n8n yet - would be good to know if this is a bug or the new behaviour going forward.

[andkit01]

It seems to be a bug introduced in the recent version, which needs to be fixed, but unfortunately it seems like it's not getting enough attention/priority for the team to address it... that's unfortunate...

[andkit01]

Not sure if there is any way to get more attention/increase the priority... this seems to be a critical bug that likely affect many n8n users.

[GaloranM]

Is there any simple way to bypass it, in this scenario?

[polilluminato]

I had the same bug some days ago but now it's gone.
I've got n8n version 1.122.4 self-hosted with Coolify on an Ubuntu Server 24.04.3 LTS.

I've got the same scenario as @GaloranM

And this is the configuration

Read mp4 from Disk	Upload a video