1. Native JavaScript file upload library
2. jQuery supported (but optional)
3. S3, Azure, & custom endpoint support
4. Fault tolerance: chunking, resume, retry, pause
   
5. Images: scaling, previews, paste
6. UI: DnD, templating, progress, initial lists
7. Also: CORS, delete, forms, validation
8. Soon: CloudFront, duplicate file detection, ...

• Don't worry about the S3 REST API
  
• Forget about constructing requests & handling errors
• Construct a policy?  No need!
• Use S3's bandwidth, not your server's
• Keep your server simple & focused

• MPE POST via form submit
  
• entire file in one request
• custom headers sent as params
• 303 from S3 to a same-origin endpoint
• IE7 requires json2.js (for policy generation)

• Uses S3 "multipart upload API"
• Upload files in chunks via XHR
  
• Each request must be signed
  

• Each request sent to S3 must be signed by server
• Secret key lives on the server
• Access key on the client
• Keys should be associated w/ limited IAM user

 var uploader = new qq.s3.FineUploader({
    element: document.getElementById("uploaderContainer"),
    request: {
        endpoint: "https://mybucket.s3.amazonaws.com",
        accessKey: "{{MY_CLIENTSIDE_IAM_USER_ACCESS_KEY}}"
    },
    signature: {
        endpoint: "/s3signatures.php"
    },
    iframeSupport: {
        localBlankPagePath: "/blankpage.html"
    }
});

• Server only necessary for static resources
• Generate short-lived limited creds via server...
• ... -or- use AWS WIF (all client-side)
• Requests are signed client-side by Fine Uploader
• WIF only possible in "modern" browsers