# 4.x Migration Guide

Chart.js 4.0 introduces a number of breaking changes. We tried keeping the amount of breaking changes to a minimum. For some features and bug fixes it was necessary to break backwars compatibility, but we aimed to do so only when worth the benefit.

## End user migration

### Charts

* Charts don't override the default tooltip callbacks, so all chart types have the same-looking tooltips.
* Default scale override has been removed if the configured scale starts with `x`/`y`. Defining `xAxes` in your config will now create a second scale instead of overriding the default `x` axis.

### Options

A number of changes were made to the configuration options passed to the `Chart` constructor. Those changes are documented below.

#### Specific changes

* The radialLinear grid indexable and scriptable options don't decrease the index of the specified grid line anymore.
* The `destroy` plugin hook has been removed and replaced with `afterDestroy`.
* Ticks callback on time scale now receives timestamp instead of a formatted label.
* `scales[id].grid.drawBorder` has been renamed to `scales[id].border.display`.
* `scales[id].grid.borderWidth` has been renamed to `scales[id].border.width`.
* `scales[id].grid.borderColor` has been renamed to `scales[id].border.color`.
* `scales[id].grid.borderDash` has been renamed to `scales[id].border.dash`.
* `scales[id].grid.borderDashOffset` has been renamed to `scales[id].border.dashOffset`.
* The z index for the border of a scale is now configurable instead of being 1 higher as the grid z index.
* Linear scales now add and subtracts `5%` of the max value to the range if the min and max are the same instead of `1`.
* If the tooltip callback returns `undefined`, then the default callback will be used.
* `maintainAspectRatio` respects container height.
* Time and timeseries scales use `ticks.stepSize` instead of `time.stepSize`, which has been removed.
* `maxTickslimit` wont be used for the ticks in `autoSkip` if the determined max ticks is less then the `maxTicksLimit`.

#### Type changes
* The order of the `ChartMeta` parameters have been changed from `<Element, DatasetElement, Type>` to `<Type, Element, DatasetElement>`.

### General
* Removed fallback to `fontColor` for the legend text and strikethrough color.
* Removed `config._chart` fallback for `this.chart` in the filler plugin.
* Removed `this._chart` in the filler plugin.