Download a file from NodeJS Server using Express

Question

How can I download a file that is in my server to my machine accessing a page in a nodeJS server?

I'm using the ExpressJS and I've been trying this:

app.get('/download', function(req, res){

  var file = fs.readFileSync(__dirname + '/upload-folder/dramaticpenguin.MOV', 'binary');

  res.setHeader('Content-Length', file.length);
  res.write(file, 'binary');
  res.end();
});

But I can't get the file name and the file type ( or extension ). Can anyone help me with that?

Solution 1

Update

Express has a helper for this to make life easier.

app.get('/download', function(req, res){
  const file = `${__dirname}/upload-folder/dramaticpenguin.MOV`;
  res.download(file); // Set disposition and send it.
});

Old Answer

As far as your browser is concerned, the file's name is just 'download', so you need to give it more info by using another HTTP header.

res.setHeader('Content-disposition', 'attachment; filename=dramaticpenguin.MOV');

You may also want to send a mime-type such as this:

res.setHeader('Content-type', 'video/quicktime');

If you want something more in-depth, here ya go.

var path = require('path');
var mime = require('mime');
var fs = require('fs');

app.get('/download', function(req, res){

  var file = __dirname + '/upload-folder/dramaticpenguin.MOV';

  var filename = path.basename(file);
  var mimetype = mime.lookup(file);

  res.setHeader('Content-disposition', 'attachment; filename=' + filename);
  res.setHeader('Content-type', mimetype);

  var filestream = fs.createReadStream(file);
  filestream.pipe(res);
});

You can set the header value to whatever you like. In this case, I am using a mime-type library - node-mime, to check what the mime-type of the file is.

Another important thing to note here is that I have changed your code to use a readStream. This is a much better way to do things because using any method with 'Sync' in the name is frowned upon because node is meant to be asynchronous.

Solution 2

Use res.download()

It transfers the file at path as an “attachment”. For instance:

var express = require('express');
var router = express.Router();

// ...

router.get('/:id/download', function (req, res, next) {
    var filePath = "/my/file/path/..."; // Or format the path using the `id` rest param
    var fileName = "report.pdf"; // The default name the browser will use

    res.download(filePath, fileName);    
});

• Read more about res.download()

Solution 3

For static files like pdfs, Word docs, etc. just use Express's static function in your config:

// Express config
var app = express().configure(function () {
    this.use('/public', express.static('public')); // <-- This right here
});

And then just put all your files inside that 'public' folder, for example:

/public/docs/my_word_doc.docx

And then a regular old link will allow the user to download it:

<a href="public/docs/my_word_doc.docx">My Word Doc</a>

Solution 4

Here's how I do it:

1. create file
2. send file to client
3. remove file

Code:

let fs = require('fs');
let path = require('path');

let myController = (req, res) => {
  let filename = 'myFile.ext';
  let absPath = path.join(__dirname, '/my_files/', filename);
  let relPath = path.join('./my_files', filename); // path relative to server root

  fs.writeFile(relPath, 'File content', (err) => {
    if (err) {
      console.log(err);
    }
    res.download(absPath, (err) => {
      if (err) {
        console.log(err);
      }
      fs.unlink(relPath, (err) => {
        if (err) {
          console.log(err);
        }
        console.log('FILE [' + filename + '] REMOVED!');
      });
    });
  });
};

Solution 5

In Express 4.x, there is an attachment() method to Response:

res.attachment();
// Content-Disposition: attachment

res.attachment('path/to/logo.png');
// Content-Disposition: attachment; filename="logo.png"
// Content-Type: image/png

View more solutions

Comments

[Thiago Miranda de Oliveira]

Thanks.. Is there a way to get this information from the fs.readFileSync? I'm using a static file in this example but I'll use this download api for any files, passing the name of it.

[Capy]

Setting output filename works with res.setHeader('Content-disposition', 'attachment; filename=' + filename); tnx!

[R J.]

how to download multiple documents using res.download() method.

[loganfsmyth]

@RJ. If you have a question, create a new one, don't leave a comment.

[frosty]

What if you want to use res.download, but change the content type header? I am trying to serve a chrome extension of my site, but the Chrome web store only allows this to work if the content type of the file is 'application/x-chrome-extension'. So, using res.download, is it possible to do that?

[loganfsmyth]

Please create a new question, comments are for commenting.

[ZachB]

Note that it appears that res.download does not use streaming.

[loganfsmyth]

@ZachB What makes you say that? It does as far as I can see.

[ZachB]

@loganfsmyth I was reading the source code and it just calls send. See similar observations posted here: stackoverflow.com/questions/13106096/…. Would be nice if I'm wrong.

[loganfsmyth]

I don't know about older versions of Express, but in 3.x it just calls .sendfile, which uses streaming. github.com/visionmedia/express/blob/…

[ZachB]

@loganfsmyth Not sure what I was looking at, but you're right -- it does stream. Thanks for correcting me.

[nembleton]

That works well for assets (although a dedicated serving proxy like nginx is recommended). But for anything that requires secured access, the accepted method is better. Generally speaking for docs and files containing information, I wouldn't recommend using the public method.

[MalcolmOcean]

you could add middleware to ensure that only appropriate users can access the files

[MalcolmOcean]

e.g. this.use('/topsecret', mGetLoggedInUser, mEnsureAccess, express.static('topsecret')) ...and then each request goes through mEnsureAccess. Of course, that means you'll need to be able to figure out a user's access level just based on the url of the secure document, or whatever.

[user137717]

@loganfsmyth How can I set the file path with res.download? The file I want to send is a directory level above and __dirname+'../otherdir' isn't correct.

[loganfsmyth]

If you have a question, please ask it as a question, don't leave a comment.

[Dana Woodman]

Express 4.x uses .set() instead of .setHeader() btw

[Besto]

I couldn't do it with the first solution, but the express helper you edited in worked like a charm. Thanks!

[summerNight]

What if the data was coming in from a HTTP request instead of a file and we had to let users download the file in a streaming way?

[Jossef Harush Kadouri]

@summerNight - well, that is a different case than the question specified. search for nodejs proxy file download response for best practice

[MikeSchem]

if you pass in the path, is this method safe for directory traversal attacks?

[loganfsmyth]

@MikeSchem It is not.

[rohitwtbs]

@loganfsmyth I just used this code to get docx on client.I am using angular5 in clent. I request the docx from a http get request.But when i get the file browser throws error. syntax error: uexpected token P at JSON position 0.

[loganfsmyth]

@rohitwtbs That sounds like you are treating to file as JSON when it isn't JSON. I can't really say why that would be.

[user1063287]

this is the only solution i have found in about two days of searching that works for my particular scenario of getting an audio file. the only thing is that i don't think res.download() works with $.ajax calls unfortunately - i had to use window.open("/api/get_audio_file");, see: stackoverflow.com/a/20177012

[1UC1F3R616]

@summerNight i am still looking for this particular solution, if some link is there then plz help

[summerNight]

@1UC1F3R616 I ended up solving the problem like this: router.get(API_PREFIX + '/file-download', function (req, res, next) { var file = process.env.FILE_DOWNLOAD_LOCATION + '/' + req.query.filename res.download(file); });

[Jossef Harush Kadouri]

@summerNight and @1UC1F3R616 note that you are vulnerable to directory traversal attacks. for instance https://.../api?filename=../../../keys/my-secret-ssl-key.pem‌​. to avoid that, you need to validate the query param

[Manny Alvarado]

I am baffled at this answer. I started my server with "node server.js". It's running, but I can't seem to get this working. This should download a file into your downloads folder in your computer no? In my setup it just doesn't work. I've been trying to do this for an hour now.

[Jhollman]

this was the Answer i looking for, Simple and Efficient