For Strapi version 3.0.0-beta.20 onward

All you need to do is to create a file at extensions/upload/config/settings.json

Cloudinary

1. Install strapi-provider-upload-cloudinary

yarn add strapi-provider-upload-cloudinary

2. Update extensions/upload/config/settings.json

{    
  "provider": "cloudinary",    
  "providerOptions": {  
    "cloud_name": "YOUR CLOUDINARY CLOUD NAME",  
    "api_key": "YOUR CLOUDINARY API KEY",  
    "api_secret": "YOUR CLOUDINARY API SECRET"    
  }  
}

AWS S3

1. Install strapi-provider-upload-aws-s3

yarn add strapi-provider-upload-aws-s3

2. Update extensions/upload/config/settings.json

{    
  "provider": "aws-s3",    
  "providerOptions": {  
    "accessKeyId": "YOUR AWS IAM ACCESS KEY",  
    "secretAccessKey": "YOUR AWS IAM SECRET KEY",  
    "region": "YOUR S3 BUCKET REGION",  
    "params": {  
        "Bucket": "YOUR S3 BUCKET NAME"  
    }  
  }  
}

Google Cloud Storage (GCS)

1. Install strapi-provider-upload-google-cloud-storage

yarn add strapi-provider-upload-google-cloud-storage

2. Update extensions/upload/config/settings.json

{    
  "provider": "google-cloud-storage",    
  "providerOptions": {  
    "serviceAccount": "YOUR GCS SERVICE ACCOUNT JSON",  
    "bucketName": "YOUR GCS BUCKET NAME",  
    "baseUrl": "https://storage.googleapis.com/YOUR GCS BUCKET NAME"    
  }  
}

And that’s it! Enjoy!

Photo by Drew Coffman on Unsplash