[Django]-Django – How to make a variable available to all templates?

What you want is a context processor, and it’s very easy to create one. Assuming you have an app named custom_app, follow the next steps:

• Add custom_app to INSTALLED_APPS in settings.py (you’ve done it already, right?);
• Create a context_processors.py into custom_app folder;

• Add the following code to that new file:

  def categories_processor(request):
   categories = Category.objects.all()            
   return {'categories': categories}
  

• Add context_processors.py to TEMPLATE_CONTEXT_PROCESSORS in settings.py

  TEMPLATE_CONTEXT_PROCESSORS += ("custom_app.context_processors.categories_processor", )
  

And now you can use {{categories}} in all the templates 😀

As of Django 1.8

To add a TEMPLATE_CONTEXT_PROCESSORS, in the settings you must add the next code:

TEMPLATES[0]['OPTIONS']['context_processors'].append("custom_app.context_processors.categories_processor")

Or include that string directly in the OPTIONS.context_processors key in your TEMPLATES setting.