Uppy with Transloadit and Dashboard Modal

Hi folks,

I’m trying to use uppy on my software to upload hundred of files using transloadit plugin.

When I selected up to 14 files it works very well, but if I selected more files, like 20, it appears a bunch of errors:

“Access to XMLHttpRequest at ‘…://api2-mudhol.transloadit.com/resumable/files/**’ from origin ‘…://localhost:3000’ has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.”

“Access to fetch at ‘…://api2-mudhol.transloadit.com/assemblies/**’ from origin ‘…://localhost:3000’ has been blocked by CORS policy: No ‘Access-Control-Allow-Origin’ header is present on the requested resource. If an opaque response serves your needs, set the request’s mode to ‘no-cors’ to fetch the resource with CORS disabled.”

“[Uppy] [23:10:20] Failed to upload IMG_9357.JPG This looks like a network error, the endpoint might be blocked by an internet provider or a firewall.
Source error: [TypeError: Failed to fetch]”

“GET …://api2-mudhol.transloadit.com/assemblies/**net::ERR_FAILED 429”

This is my code in React:

const uppy = new Uppy({
restrictions: {
allowedFileTypes: [‘image/’, 'video/’, ‘audio/*’, ‘.docx’, ‘.pdf’, ‘.doc’],
maxNumberOfFiles: 100,
minNumberOfFiles: 1,
autoProceed: false,
proudlyDisplayPoweredByUppy: false,

uppy.use(Transloadit, {
getAssemblyOptions (file) {
return ({
params: {
auth: { key: ‘’ },
template_id: '
fields: {
folder_name: albumId,
file_uuid: uuid(),
file_name: file.name,
limit: 1,

strings: {
dropHereOr: ‘Drop here or %{browse}’,
browse: 'browse ',

I’m not understanding why sometimes I got these errors, and other times not.

Just for share. I could fix it by updating the uppy package.

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