filters

concat 2 strings: {{ "hello "|add:"john doe" }}

capitalize: {{ "hello there!"|capfirst }}

capitalize each word: {{ "hello there!"|title }}

default value: {{ simple.nothing|default:"n/a" }}

default only if nil: {{ nil|default_if_none:"n/a" }}

variable is safe: {{ var|safe }}

truncate string: {{ "Joel is a slug"|truncatechars:9 }} -> Joel i...

pluralize: customer{{ 2|pluralize }}

urlencode: {{ "http://www.example.org/foo?a=b&c=d"|urlencode }}

convert to integer: {{ var|integer }}

join a list of string: {{ items | join:", " }}

newline to <br>: {{ var | linebreaks | safe }}

escape var for js: {{ var | escapejs }}

reference:

https://github.com/flosch/pongo2/blob/master/template_tests/filters.tpl