Resume Upload

Resume an interrupted chunked upload. When a connection drops, chunks already uploaded are skipped on retry, continuing from where it left off.

var uploader = new MultipleUpload(document.getElementById('demo-resume'), {
 uploadUrl: '/api/upload',
 multiple: true,
 chunked: true,
 chunkSize: 1 * 1024 * 1024, // 1 MB for demo
 retries: 5,
 onTaskError: function(task, error) {
 document.getElementById('resume-status').textContent =
 'Upload interrupted: ' + error + ' ?will auto-retry';
 },
 onTaskComplete: function(task) {
 document.getElementById('resume-status').textContent =
 task.fileName + ' uploaded successfully (resumed if interrupted)';
 }
});

Continuing where it stopped

With chunking on, the client can ask the server which chunks it already holds and send only the rest. A 4 GB upload interrupted at 90% resumes as a 400 MB upload rather than starting over.

Two different kinds of resume

Within a session, resume is automatic after a network failure. Across a reload or a crash it needs persistState, and how much survives depends on the adapter: localStorage keeps the bookkeeping so the user re-picks the files, IndexedDB can keep the blobs too and resumes with no user action at all.