Heroku: No Default Language Could Be Detected for This App

Heroku: No default language could be detected for this app error thrown for node app

Heroku has a set of default buildpacks, used when it needs to detect the language of your app.

In order to do that detection, it runs the bin/detect command of each of those default buildpacks, until one of them returns a 0 exit code.

This is the command for the node buildpack.

As you can see, it requires a package.json to be located at the root of your app, not in a subfolder.

This is the difference causing your build to fail. You need to put your app at the root of your git repository.

heroku: no default language could be detected for this app

I can't remember how I fixed this but looking at the Date Modified in my files after I posted this question I created two files:

runtime.txt (thanks rurp) which contains:

python-3.5.2

Procfile which contains:

web: gunicorn projectname.wsgi --log-file -

This is a Django project and projectname.wsgi leads to a wsgi.py located at

projectname/wsgi.py

This contains:

import os
import signal

import sys
import traceback

import time
from django.core.wsgi import get_wsgi_application
from whitenoise.django import DjangoWhiteNoise

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "projectname.settings")

application = get_wsgi_application()
application = DjangoWhiteNoise(application)

Heroku: No default language could be detected for this app for python even with runtime.txt

A possible solution to this problem can be specifying the buildpack during app creation like :

$ heroku create myapp --buildpack heroku/python

or after app creation like:

$ heroku buildpacks:set heroku/python

Refer Docs : Heroku Docs

The other problem I figured was that I had unnecessary package.json and other files in my django project. I solved it by removing unnecessary files from my app directory.

Since these files were obstructing the automatic detection of buildpack.

Another reason of failed detection could be wrong folder structure of your app. The Procfile and other heroku files should be right at the start of the git directory otherwise your app won't get detected.

Ruby-heroku No default language could be detected for this app

Gemfile and gemfile are different things. Rename gemfile to Gemfile and gemfile.lock to Gemfile.lock, commit that change, and deploy again.

If you're using a filesystem that doesn't distinguish between those things (like most Windows filesystems) it might be tricky to do. See Change case of a file on Windows?

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