Say we want …

• to create a Gallery that has a name and has_many :images, which in turn have a caption
• to offer the user a single form to create a gallery with any number of images
• immediate uploads with a progress bar per image
• a snapp...

When you allow file uploads in your app, a user might upload content that hurts other users.

Our primary concern here is users uploading .html or .svg files that can run JavaScript and [possibly hijack another user's session](#section-att...

A flat folder structure can be cool if you have only a few folders but can be painful for huge amounts. We recently had this issue in a project with more than 100.000 attachments, where we used a structure like this `/attachments/123456789/file.pd...

To upload a file via AJAX (e.g. from an <input type='file'>) you need to wrap your params in a FormData object.

You can initialize a FormData using the contents of a form:

va...

1. Saving files to a directory that is not shared between deploys or servers

If you save your uploads to a made up directory like "RAILS_ROOT/uploads", this directory goes away after every deploy (since every release gets a new). Also this di...

Carrierwave's BaseUploader can have some validations that you can use by overriding a certain method, which's expected name is hard coded. A popular example is extension_allowlist, which returns an array of strings and let's you only upload fi...

While upgrading CarrierWave from version 0.11.x to 3.x, we encountered some very nasty fails. Below are the basic changes you need to perform and some behavior you may eventually run into when upgrading your application. This aims to save you some...

If in your application your users pass along params that result in filenames, like invoices/generated?number=123. This could be your (very careless) controller method:

def generated
  send_file File.join(Rails.root, 'shared', 'invoices'...

Attaching files to a field that is handled by Carrierwave uploaders (or maybe any other attachment solution for Rails) in tests allows different approaches. Here is a short summary of the most common methods.

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