# `keys` The `keys` filter returns the keys of an array. It is useful when you want toiterate over the keys of an array: <table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1 2 3</pre></div></td><td class="code"><div class="highlight"><pre>{% for key in array|keys %} ... {% endfor %} </pre></div></td></tr></table>