backend-file-uploads

Backend File Uploads

When adding file uploads to backend Hono routes, use the existing file middleware from apps/backend/src/middleware/file. Read apps/backend/src/middleware/file/README.md before implementing or changing upload behavior.

• Import upload helpers from @backend/middleware/file.
• Use fileUpload(...) as route middleware before the Hono handler.
• Prefer diskStorage(...) for production uploads and larger files.
• Use memoryStorage() only for small files that need direct buffer access.
• Always configure appropriate limits, especially fileSize and file count limits.
• Use fileFilter when uploads must be restricted by MIME type or other file metadata.
• Read uploaded data from Hono context with c.get("file"), c.get("files"), or c.get("body") according to the upload method.

Example:

import { fileUpload, diskStorage } from "@backend/middleware/file";

app.post(
  "/upload",
  fileUpload({
    storage: diskStorage({ destination: "./uploads" }),
    limits: {
      fileSize: 5 * 1024 * 1024,
      files: 1,
    },
    fileFilter: (_req, file, cb) => {
      cb(null, file.mimetype.startsWith("image/"));
    },
  }).single("file"),
  async (c) => {
    const file = c.get("file");

    return c.json({ fileId: file.filename });
  },
);