Django template tags: check the request agent is Facebook.

facebook_tags.py

from django import template

register = template.Library()


@register.assignment_tag(takes_context=True)
def is_facebook(context):
    request = context.get('request')
    a = request.META['HTTP_USER_AGENT']
    f = ['facebookexternalhit/1.1 (+https://www.facebook.com/externalhit_uatext.php)',
         'facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)']
    if a in f:
        return True
    return False