File upload

Examples

The basic FileUpload component can accept a file via browse or drag-and-drop, and behaves like a standard form field with its value and onChange props. The type prop determines how the FileUpload component behaves upon accepting a file, what type of value it passes to its onChange prop, and what type it expects for its value prop.

Text files

If type="text" is passed (and hideDefaultPreview is not), a TextArea preview will be rendered underneath the filename bar. When a file is selected, its contents will be read into memory and passed to the onChange prop as a string (along with its filename). Typing/pasting text in the box will also call onChange with a string, and a string value is expected for the value prop.

A user can always type instead of selecting a file, but by default, once a user selects a text file from their disk they are not allowed to edit it (to prevent unintended changes to a format-sensitive file). This behavior can be changed with the allowEditingUploadedText prop:

Restricting file size and type

Any props accepted by react-dropzone's Dropzone component can be passed as a dropzoneProps object in order to customize the behavior of the Dropzone, such as restricting the size and type of files allowed. The following example will only accept CSV files smaller than 1 KB. Note that file type determination is not reliable across platforms (see the note on react-dropzone's docs about the accept prop), so be sure to test the behavior of your file upload restriction on all browsers and operating systems targeted by your application.

IMPORTANT: A note about security

Restricting file sizes and types in this way is for user convenience only, and it cannot prevent a malicious user from submitting anything to your server. As with any user input, your application should also validate, sanitize and/or reject restricted files on the server side.

Other file types

If no type prop is specified, the component will not read files directly. When a file is selected, a File object will be passed to onChange and your application will be responsible for reading from it (e.g. by using the FileReader API or attaching it to a FormData object). A File object will also be expected for the value prop instead of a string, and no preview of the file contents will be shown by default. The onReadStarted and onReadFinished callbacks will also not be called since the component is not reading the file.

Customizing the file preview

Regardless of type, the preview area (the TextArea, or any future implementations of default previews for other types) can be removed by passing hideDefaultPreview, and a custom one can be rendered by passing children.

Bringing your own file browse logic

FileUpload is a thin wrapper around the FileUploadField presentational component. If you need to implement your own logic for accepting files, you can instead render a FileUploadField directly, which does not include react-dropzone and requires additional props (e.g. onBrowseButtonClick, onClearButtonClick, isDragActive).

Note that the isLoading prop is styled to position the spinner dead center above the entire component, so it should not be used with hideDefaultPreview unless a custom empty-state preview is provided via children. The below example prevents isLoading and hideDefaultPreview from being used at the same time. You can always provide your own spinner as part of the children!