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---

title: generatePresignedDownloadUrl description: Generate a presigned URL for secure file downloads from S3-compatible storage

<Callout title="Backend Implementation Required" type="error"> This function **must be implemented on your backend server** and cannot be safely exposed to the frontend. The function handles sensitive S3 credentials and should only be called from your server-side code. </Callout> <Callout title="CORS Configuration Required" type="error"> You **must configure CORS settings** on your S3 bucket or storage provider to allow your frontend domain to download files using the generated presigned URLs. Without proper CORS configuration, downloads will fail with cross-origin errors. </Callout>

Usage

import { generatePresignedDownloadUrl } from '@/lib/generate-presigned-download-url';

const downloadUrl = await generatePresignedDownloadUrl(
  'file-key',
  3600 // expires in 1 hour
);

Installation

<InstallTabs component="generate-presigned-download-url" />

Parameters

| Parameter | Type | Description | Default | |-------------|----------|---------------------------------------|---------| | key | string | The S3 object key of the file | - | | expiresIn | number | URL expiration time in seconds | 3600 |

Returns

A string containing the presigned download URL that allows temporary access to the file.

Environment Variables

This function requires the following environment variables:

S3_REGION=your-region
S3_ENDPOINT=your-s3-endpoint
S3_ACCESS_KEY=your-access-key
S3_SECRET_KEY=your-secret-key
S3_BUCKET_NAME=your-bucket-name

Dependencies

• @aws-sdk/client-s3
• @aws-sdk/s3-request-presigner

Implementation

import { GetObjectCommand } from '@aws-sdk/client-s3';
import { getSignedUrl } from '@aws-sdk/s3-request-presigner';

import { getS3Client } from '@/lib/s3-client';

export async function generatePresignedDownloadUrl(
  key: string,
  expiresIn = 3600,
) {
  try {
    const command = new GetObjectCommand({
      Bucket: process.env.S3_BUCKET_NAME,
      Key: key,
    });

    const url = await getSignedUrl(getS3Client(), command, { expiresIn });
    return url;
  } catch (err) {
    console.error({ err }, 'Failed to generate download URL');
    throw new Error('Failed to generate download URL');
  }
}

Frontend Integration

<Card title="downloadFile" href="/docs/storage/download-file"> Generate presigned URLs for secure file uploads to cloud storage </Card>

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