[Django]-A Better Django Admin ManyToMany Field Widget

you could try using a raw id in the admin.
and the django docs:
http://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.raw_id_fields

if you are looking for something with auto-complete you might want to look at this as a starting point http://code.djangoproject.com/wiki/AutoCompleteSolutions

and finally a very simplistic inline Example:

models.py

class SomeModel(models.Model):
    users = models.ManyToMany(User)

admin.py:

class SomeModelAdmin(admin.ModelAdmin):
    raw_id_fields = ("users",)

I haven’t actually played with it but I found this promising looking library referenced elsewhere.

It appears to do exactly what I wanted. Rather than loading the entire list of related objects (regardless of how many there are!) and presenting you with a picker to select a few of them, as filter_horizontal does, it presents a search/filter box and uses typeahead/autocomplete calls to retrieve results dynamically. This is great for the case where you have maybe 5000 users and want to pick 3 or 4 of them without waiting for 5k <option> elements to download and render.

This is an old question, but I want to add an answer here for people who find this just like I did: this situation is exactly what Django inline admins are for. Specifically, I use TabularInlines with raw id fields for many-to-many relations that have too many choices.

https://docs.djangoproject.com/en/2.1/ref/contrib/admin/#django.contrib.admin.TabularInline

You can try using Inline model as such –

class ManyToManyInline(TabularInline): 
    model = MyModel.many_to_many_field_name.through 
    raw_id_fields = ("render_raw_id_using_this",) 

@register(MyModel) 
class YourAdminClass(AnyBaseClass): 
    exclude = ("many_to_many_field_name",) 
    inlines = (ManyToManyInline,) 

Now there is another issue I faced, finding "render_raw_id_using_this" field name.

So, I moved to shell and tried finding fields in through model as such –

In [1]: MyModel.many_to_many_field_name.through._meta.fields 
Out [1]: (<django.db.models.fields.AutoField: id>, <django.db.models.fields.related.ForeignKey: fieldname1>, <django.db.models.fields.related.ForeignKey: fieldname2>) 

So, I replaced render_raw_id_using_this with fieldname1

Similarly, you can use these field names to render raw id instead of drop down list in Inline model.