Filtering

You may specify filters to allow (or deny) only certain content types, file extensions, or file sizes in a FS.Collection. Use the filter option.

Images = new FS.Collection("images", {
  filter: {
    maxSize: 1048576, //in bytes
    allow: {
      contentTypes: ['image/*'],
      extensions: ['png']
    },
    deny: {
      contentTypes: ['image/*'],
      extensions: ['png']
    },
    onInvalid: function (message) {
      if (Meteor.isClient) {
        alert(message);
      } else {
        console.log(message);
      }
    }
  }
});

Alternatively, you can pass your filters object to myFSCollection.filters().

To be secure, this must be added on the server; however, you should use the filter option on the client, too, to help catch many of the disallowed uploads there and allow you to display a helpful message with your onInvalid function.

You can mix and match filtering based on extension or content types. The contentTypes array also supports "image/*" and "audio/*" and "video/*" like the "accepts" attribute on the HTML5 file input element.

If a file extension or content type matches any of those listed in allow, it is allowed. If not, it is denied. If it matches both allow and deny, it is denied. Typically, you would use only allow or only deny, but not both. If you do not pass the filter option, all files are allowed, as long as they pass the tests in your FS.Collection.allow() and FS.Collection.deny() functions.

The extension checks are used only when there is a filename. It's possible to upload a file with no name. Thus, you should generally use extension checks only in addition to content type checks, and not instead of content type checks.

The file extensions must be specified without a leading period. Extension matching is case-insensitive.