How to get the v-for index in Vue.js?

Declare an index variable:

<div v-for="(item, index) in items" :key="item.name">

</div>

Demo:

new Vue({
  el: '#app',
  data: {
    items: [{name: 'a'}, {name: 'b'}]
  }
})

<script src="https://unpkg.com/vue"></script>

<div id="app">
  <div v-for="(item, index) in items" :key="item.name">
    {{ index }}: {{ item.name }}
  </div>
</div>

Official docs section – Mapping an Array to Elements with v-for (emphasis mine):

Inside v-for blocks we have full access to parent scope properties. v-for also supports an optional second argument for the index of the current item.