expressjs.com/_includes/api/en/4x/res-sendFile.md

res.sendFile(path [, options] [, fn])

`res.sendFile()` is supported by Express v4.8.0 onwards.

Transfers the file at the given path. Sets the Content-Type response HTTP header field based on the filename's extension. Unless the root option is set in the options object, path must be an absolute path to the file.

The following table provides details on the options parameter.

Property	Description	Default	Availability
maxAge	Sets the max-age property of the Cache-Control header in milliseconds or a string in ms format	0
root	Root directory for relative filenames.
lastModified	Sets the Last-Modified header to the last modified date of the file on the OS. Set false to disable it.	Enabled	4.9.0+
headers	Object containing HTTP headers to serve with the file.
dotfiles	Option for serving dotfiles. Possible values are "allow", "deny", "ignore".	"ignore"
acceptRanges	Enable or disable accepting ranged requests.	true	4.14+
cacheControl	Enable or disable setting Cache-Control response header.	true	4.14+

The method invokes the callback function fn(err) when the transfer is complete or when an error occurs. If the callback function is specified and an error occurs, the callback function must explicitly handle the response process either by ending the request-response cycle, or by passing control to the next route.

Here is an example of using res.sendFile with all its arguments.

app.get('/file/:name', function (req, res, next) {

  var options = {
    root: __dirname + '/public/',
    dotfiles: 'deny',
    headers: {
        'x-timestamp': Date.now(),
        'x-sent': true
    }
  };

  var fileName = req.params.name;
  res.sendFile(fileName, options, function (err) {
    if (err) {
      console.log(err);
      res.status(err.status).end();
    }
    else {
      console.log('Sent:', fileName);
    }
  });

});

The following example illustrates using res.sendFile to provide fine-grained support for serving files:

app.get('/user/:uid/photos/:file', function(req, res){
  var uid = req.params.uid
    , file = req.params.file;

  req.user.mayViewFilesFrom(uid, function(yes){
    if (yes) {
      res.sendFile('/uploads/' + uid + '/' + file);
    } else {
      res.status(403).send('Sorry! you cant see that.');
    }
  });
});

For more information, or if you have issues or concerns, see send.