LimeSurvey version: LimeSurvey Cloud Version 6.15.5
Survey theme/template: fruity general
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We want to use a survey to provide proof of documentation, for which large(r) amounts of documents need to be updated 10-20 a time. The general one-by-one upload function is very slow, so we would like to select several documents at once. Is that possible? Or other ideas to speed the upload process up?

I don't think Limesurvey allows to upload more than one document at once. I guess this is due to the fact that yo need to add information as for example the name.

Not sure if it would be possible to add some third party upload libraries to Limesurvey.

I feel that the upload question has very little priority, also because it is probably not as widely and frequently used as other question types.

Of course, in certain scenarios the upload question can be the main question, like in your case.

There are quite a few upload libraries based on JS out there, even open source. But I am no expert on this and if it is possible to integrate them with Limesurvey.

Hi,
using the cloud version you are a bit restricted.
You can't use plugins and have no direct access to the database.

But you can zip the files before. Then there is only one upload.

And what means "very slow". 
The upload of 10 files took me 2:15 minutes. I should say this is acceptable.

Joffm