payloadcms/payload · error · FileRetrievalError

Unable to determine mimetype for file: ${importDoc.filename}

Error message

Unable to determine mimetype for file: ${importDoc.filename}

What it means

After retrieving the file, the createCollectionImport task derives a mimetype from file.mimetype falling back to importDoc.mimeType. If both are falsy it throws a FileRetrievalError, because the mimetype is required to route CSV vs JSON parsing.

Source

Thrown at packages/plugin-import-export/src/import/getCreateImportCollectionTask.ts:72

      if (!collectionConfig) {
        throw new Error(`Collection config not found for: ${importCollection}`)
      }

      // Retrieve the file using getFileFromDoc (handles both local and cloud storage)
      const file = await getFileFromDoc({
        collectionConfig,
        doc: {
          filename: importDoc.filename as string,
          mimeType: importDoc.mimeType as string | undefined,
          url: importDoc.url as string | undefined,
        },
        req,
      })

      const fileMimetype = file.mimetype || (importDoc.mimeType as string)

      if (!fileMimetype) {
        throw new FileRetrievalError(
          req.t,
          `Unable to determine mimetype for file: ${importDoc.filename}`,
        )
      }

      const result = await createImport({
        name: (importDoc.filename as string) || 'import',
        batchSize,
        collectionSlug: importDoc.collectionSlug as string,
        debug,
        defaultVersionStatus,
        file: {
          name: importDoc.filename as string,
          data: file.data,
          mimetype: fileMimetype,
        },
        format: fileMimetype === 'text/csv' ? 'csv' : 'json',
        importMode: (importDoc.importMode as 'create' | 'update' | 'upsert') || 'create',

View on GitHub (pinned to 00c58b35c0)

Solutions

1. Backfill importDoc.mimeType for existing records.
2. Ensure new uploads persist mimeType (set it in the upload handler / collection fields).
3. If the file is local, confirm getFileByPath returns a mimetype (depends on the file extension detection).

const importDoc = await req.payload.findByID({ id: importId, collection: importCollection })
if (!importDoc) throw new Error('import doc missing')
const mimetype = (await getFileFromDoc({ collectionConfig, doc: importDoc, req })).mimetype || importDoc.mimeType
if (!mimetype) throw new Error('no mimetype; backfill importDoc.mimeType')

const hasMimeType = (d: { mimeType?: unknown }): boolean =>
  typeof d.mimeType === 'string' && d.mimeType.length > 0

When it happens

Trigger: The stored import document has no mimeType field and the retrieved file's mimetype is undefined. Common when uploads were persisted without a mimeType or a storage adapter did not populate it.

Common situations: Older import records created before mimeType was tracked; custom upload flow that omits mimeType; storage adapter that strips metadata.

Related errors

• Unable to determine mimetype for file: ${doc.filename}
• No file data provided for import
• Unable to determine mimetype for file: ${doc.filename}
• Unable to retrieve file: missing filename or url
• Collection with slug ${collectionSlug} not found

AI-assisted analysis of payloadcms/payload@00c58b35c0 (2026-08-12). Data as JSON: /api/errors/3dfeff91751a0377. Report an issue: GitHub.