how to check if file exists in Firebase Storage?

Question

When using the database you can do snapshot.exists() to check if certain data exists. According to the docs there isn't a similar method with storage.

https://firebase.google.com/docs/reference/js/firebase.storage.Reference

What is the proper way of checking if a certain file exists in Firebase Storage?

score 36 · Accepted Answer · edited Apr 21 '21 at 21:28

36

Firebase added an .exists() method. Another person responded and mentioned this, but the sample code they provided is incorrect. I found this thread while searching for a solution myself, and I was confused at first because I tried their code but it always was returning "File exists" even in cases when a file clearly did not exist.

exists() returns an array that contains a boolean. The correct way to use it is to check the value of the boolean, like this:

const storageFile = bucket.file('path/to/file.txt');
storageFile
  .exists()
  .then((exists) => {
        if (exists[0]) {
          console.log("File exists");
        } else {
          console.log("File does not exist");
        }
     })

I'm sharing this so the next person who finds this thread can see it and save themselves some time.

edited Apr 21 '21 at 21:28

jsiot

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answered Mar 02 '21 at 15:10

most200

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Thanks for this. Is there any Google documentation for this method? I can't seem to find it. – Grant Singleton Apr 28 '21 at 21:46
@GrantSingleton I have not been able to find any official documentation on it myself either. – most200 Apr 29 '21 at 02:00
@GrantSingleton Correction: there is one reference. Another poster shared it in a comment further down on this same topic, if you scroll down. https://googleapis.dev/nodejs/storage/5.1.1/File.html#exists-examples – most200 Apr 29 '21 at 02:02
4

make sure to check `exists[0]` and not `exists`. that was my ire – Patrick Michaelsen Jun 24 '21 at 16:49
Where does bucket come from? – Brandon Pillay Sep 20 '21 at 19:01
1

@BrandonPillay For me it comes from: `const fbAdmin = require('firebase-admin'); const bucketName = projectId + '.appspot.com'; const bucket = fbAdmin.storage().bucket(bucketName);` – most200 Sep 21 '21 at 01:43
are there any costs associated with this method? – snack overflow May 04 '22 at 20:27
1

@dovigz I'm not sure on costs. Here is the link to cloud storage pricing: https://cloud.google.com/storage/pricing#pricing To me it feels like exists() could be a class B operation (which cost $.004 per 10k in 2022 pricing), but it is not explicitly listed. Firebase also includes 50k free operations per month. I don't use exists at a high enough volume to see any impact on my current costs. You could try running a quantity of exists operations to see if they show up in your billing, or contact Firebase support to ask if they can clarify. – most200 May 08 '22 at 00:08
1

since 5.1.1 was long ago, and google is not a good resource for finding these API docs, just confirming this IS an official documented function, but afaict ONLY in the server/admin API. Presumably the /latest docs path will remain valid even as versions change: https://googleapis.dev/nodejs/storage/latest/File.html#exists – NNSkelly Jun 16 '23 at 18:55

score 33 · Answer 2 · answered Jun 10 '16 at 16:21

33

You can use getDownloadURL which returns a Promise, which can in turn be used to catch a "not found" error, or process the file if it exists. For example:

storageRef.child("file.png").getDownloadURL().then(onResolve, onReject);

function onResolve(foundURL) {
    //stuff
}

function onReject(error) {
    console.log(error.code);
}

answered Jun 10 '16 at 16:21

mjr

777
1
10
26

10

Warning: might be costly if you have several thousands of documents as downloading url will be priced by Firebase. – Corentin Houdayer Jul 28 '20 at 12:54
@CorentinHoudayer He is giving reference with file_name. So there is only one file. Why will it be costly? – Abu Saeed Apr 02 '22 at 04:41
@Unknown2433 If you download only this document once in your app for a single user, the answer is no. If you do it multiple times (each app launch) with multiple files, yes it will become pretty expensive. Take a look at firebase pricing and you can estimate your budget based on this. – Corentin Houdayer Apr 03 '22 at 12:59
@CorentinHoudayer I am not downloading the file. I am requesting for the download url of the file and calling `getDownloadUrl` is free. Isn't it? – Abu Saeed Apr 03 '22 at 17:37
@Unknown2433 It isn't free as you will consume bandwidth which has a cost. I had an app where I was showing wallpapers, using this request 50 times / per session on average was really expensive for me. Even more if you download the file using URL of course. In order to know the consumed bandwidth, you might do your own test on Android with a specific app for instance. – Corentin Houdayer Apr 04 '22 at 19:27
@CorentinHoudayer I know about bandwidth cost which is the worst thing about firebase storage. But I didn't knew that calling `getDownloadUrl` uses bandwidth. Thanks for the info – Abu Saeed Apr 05 '22 at 12:06

score 10 · Answer 3 · answered Jun 10 '16 at 16:17

10

I believe that the FB storage API is setup in a way that the user only request a file that exists.

Thus a non-existing file will have to be handled as an error: https://firebase.google.com/docs/storage/web/handle-errors

answered Jun 10 '16 at 16:17

Yacine

147
10

score 6 · Answer 4 · answered Jul 21 '20 at 09:30

6

I've found a nice solution while keeping within the Node.js Firebase Gogole Cloud Storage SDK using the File.exists, taught it would be ideal to share for those searching.

const admin = require("firebase-admin");
const bucket = admin.storage().bucket('my-bucket');

const storageFile = bucket.file('path/to/file.txt');
storageFile
  .exists()
  .then(() => {
    console.log("File exists");
  })
  .catch(() => {
    console.log("File doesn't exist");
  });

Google Cloud Storage: Node.js SDK version 5.1.1 (2020-06-19) at the time of writing

answered Jul 21 '20 at 09:30

kylewelsby

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The example code is wrong. Check the example on the docs: https://googleapis.dev/nodejs/storage/5.1.1/File.html#exists-examples – Pier Mar 03 '21 at 15:49
Bucket doesn't have property file – Roman Soviak Feb 04 '23 at 11:24

score 1 · Answer 5 · answered Jul 09 '21 at 16:57

1

That worked for me

  Future<bool> fileExists(String file) async {
    var parts = file.split('/');
    var path = parts.sublist(0, parts.length - 1).join('/');
    var listResult = await _storage.ref().child(path).list();
    return listResult.items.any((element) => element.fullPath == file);
  }

answered Jul 09 '21 at 16:57

Diogo Pio

21
1

2

A good answer will always include an explanation why this would solve the issue, so that the OP and any future readers can learn from it – Tyler2P Jul 09 '21 at 17:32

how to check if file exists in Firebase Storage?

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