Breaking Changes

This page lists all Vue 3 breaking changes from Vue 2.

While it looks like a lot has changed, a lot of what you know and love about Vue is still the same; but we wanted to be as thorough as possible and provide detailed explanations and examples for every documented change.

Details

Global API

• Global Vue API is changed to use an application instance
• Global and internal APIs have been restructured to be tree-shakable

Template Directives

• v-model usage on components has been reworked, replacing v-bind.sync
• key usage on <template v-for> and non-v-for nodes has changed
• v-if and v-for precedence when used on the same element has changed
• v-bind="object" is now order-sensitive
• v-on:event.native modifier has been removed

Components

• Functional components can only be created using a plain function
• functional attribute on single-file component (SFC) <template> and functional component option are deprecated
• Async components now require defineAsyncComponent method to be created
• Component events should now be declared with the emits option

Render Function

• Render function API changed
• $scopedSlots property is removed and all slots are exposed via $slots as functions
• $listeners has been removed / merged into $attrs
• $attrs now includes class and style attributes

Custom Elements

• Custom element checks are now performed during template compilation
• Special is attribute usage is restricted to the reserved <component> tag only

Other Minor Changes

• The destroyed lifecycle option has been renamed to unmounted
• The beforeDestroy lifecycle option has been renamed to beforeUnmount
• Props default factory function no longer has access to this context
• Custom directive API changed to align with component lifecycle and binding.expression removed
• The data option should always be declared as a function
• The data option from mixins is now merged shallowly
• Attributes coercion strategy changed
• Some transition classes got a rename
• <TransitionGroup> now renders no wrapper element by default
• When watching an array, the callback will only trigger when the array is replaced. If you need to trigger on mutation, the deep option must be specified.
• <template> tags with no special directives (v-if/else-if/else, v-for, or v-slot) are now treated as plain elements and will result in a native <template> element instead of rendering its inner content.
• Mounted application does not replace the element it's mounted to
• Lifecycle hook: events prefix changed to vnode-

Removed APIs

• keyCode support as v-on modifiers
• $on, $off and $once instance methods
• Filters
• Inline templates attributes
• $children instance property
• propsData option
• $destroy instance method. Users should no longer manually manage the lifecycle of individual Vue components.
• Global functions set and delete, and the instance methods $set and $delete. They are no longer required with proxy-based change detection.