A small component for building file upload fields of any type, for example a simple file upload button or an image gallery field with drag and drop support and preview of selected images.


npm install --save react-butterfiles

Or if you prefer yarn:

yarn add react-butterfiles

Quick Example:

Create a simple file field which consists of a drop zone and a file upload button (for cases where drag
and drop is not convenient). Multiple PDF / JPG files are accepted, but with the following restrictions:

  • 3 files max
  • max 2MB in size per file
  • max 10MB in size for the whole selection
import Files from "react-butterfiles";
    onSuccess={files => this.setState({ files })}
    onError={errors => this.setState({ errors })}
    {({ browseFiles, getDropZoneProps }) => (
            <div {...getDropZoneProps({ className: "myDropZone" })}/>
            <button onClick={browseFiles}>Select files...</button>
                { => (
                    <li key={}>{}</li>
                { => (
                    <li key={}>
                        {} - {error.type}

More examples on


Prop Type Default Description
accept array [] Defines which file types will be accepted. Example: ["application/pdf"].
multiple boolean false Allow multiple file selection by setting this prop to `true.
maxFileSize string "2mb" Defines maximum file size (bytes lib used behind the scenes). Example: "10mb"
multipleMaxSize string "10mb" Useful only if multiple prop is set to true. Defines max. file size of all selected files.
multipleMaxCount number null Useful only if multiple prop is set to true. Defines max. allowed selected files.
convertToBase64 boolean false If true, selected files will also be converted to baser64 format (useful when working with images / thumbnails).
onSuccess (files: Array<SelectedFile>) => void undefined Callback that will get executed once a valid file selection has been made (via browse files dialog or drag and drop).
onError (errors: Array<FileError>) => void undefined Callback that will get executed once an invalid file selection has been made. More info about possible errors below.

Render (children) prop

Render prop gives you access to two callbacks:

Prop Type Description
browseFiles BrowseFilesParams => void Once executed, file browser will be shown. Useful for file upload buttons. The callback can also accept custom onSuccess and onError callbacks, that will override the main ones.
getDropZoneProps (additionalProps: ?Object) => Object Props that need to be spread to a drop zone. You can add additional props if needed, for example className or style.

Note that you don't need to use both callbacks, you can use only one if that's your requirement.
For example, to create a simple file field, you would only need to use the browseFiles callback.

Selection error types

While selecting and droping files, if there are one or more that do not comply with the rules that were set via props, an onError callback will be triggered, with all of the errors passed as the first argument.

Every error in the array will have one of the following error types.

Type Description
unsupportedFileType This can only happen via drag and drop since file browser dialog won't let users choose files of invalid type.
maxSizeExceeded One or more file sizes are greater than maxFileSize value.
multipleMaxCountExceeded User selected more files than allowed (more than multipleMaxCount).
multipleMaxSizeExceeded User selected one or more files with their total size greater than allowed (more than multipleMaxSize).
multipleNotAllowed This can only happen via drag and drop since file browser dialog won't let users select two or more files if multiple was not set to true.