Tooltip

Tooltip Configuration

Namespace: options.plugins.tooltip, the global options for the chart tooltips is defined in Chart.defaults.plugins.tooltip.

Position Modes

Possible modes are:

• 'average'
• 'nearest'

'average' mode will place the tooltip at the average position of the items displayed in the tooltip. 'nearest' will place the tooltip at the position of the element closest to the event position.

New modes can be defined by adding functions to the Chart.Tooltip.positioners map.

Example:

/**
 * Custom positioner
 * @function Tooltip.positioners.myCustomPositioner
 * @param elements {Chart.Element[]} the tooltip elements
 * @param eventPosition {Point} the position of the event in canvas coordinates
 * @returns {Point} the tooltip position
 */
const tooltipPlugin = Chart.registry.getPlugin('tooltip');
tooltipPlugin.positioners.myCustomPositioner = function(elements, eventPosition) {
    /** @type {Tooltip} */
    var tooltip = this;
    /* ... */
    return {
        x: 0,
        y: 0
    };
};

Alignment

The titleAlign, bodyAlign and footerAlign options define the horizontal position of the text lines with respect to the tooltip box. The following values are supported.

• 'left' (default)
• 'right'
• 'center'

These options are only applied to text lines. Color boxes are always aligned to the left edge.

Sort Callback

Allows sorting of tooltip items. Must implement at minimum a function that can be passed to Array.prototype.sort (opens new window). This function can also accept a third parameter that is the data object passed to the chart.

Filter Callback

Allows filtering of tooltip items. Must implement at minimum a function that can be passed to Array.prototype.filter (opens new window). This function can also accept a fourth parameter that is the data object passed to the chart.

Tooltip Callbacks

Namespace: options.plugins.tooltip.callbacks, the tooltip has the following callbacks for providing text. For all functions, this will be the tooltip object created from the Tooltip constructor.

Namespace: data.datasets[].tooltip.callbacks, items marked with Yes in the column Dataset override can be overridden per dataset.

All functions are called with the same arguments: a tooltip item context. All functions must return either a string or an array of strings. Arrays of strings are treated as multiple lines of text.

Label Callback

The label callback can change the text that displays for a given data point. A common example to show a unit. The example below puts a '$' before every row.

var chart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        plugins: {
            tooltip: {
                callbacks: {
                    label: function(context) {
                        var label = context.dataset.label || '';
                        if (label) {
                            label += ': ';
                        }
                        if (context.parsed.y !== null) {
                            label += new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(context.parsed.y);
                        }
                        return label;
                    }
                }
            }
        }
    }
});

Label Color Callback

For example, to return a red box for each item in the tooltip you could do:

var chart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        plugins: {
            tooltip: {
                callbacks: {
                    labelColor: function(context) {
                        return {
                            borderColor: 'rgb(255, 0, 0)',
                            backgroundColor: 'rgb(255, 0, 0)'
                        };
                    },
                    labelTextColor: function(context) {
                        return '#543453';
                    }
                }
            }
        }
    }
});

Label Point Style Callback

For example, to draw triangles instead of the regular color box for each item in the tooltip you could do:

var chart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        plugins: {
            tooltip: {
                usePointStyle: true,
                callbacks: {
                    labelPointStyle: function(context) {
                        return {
                            pointStyle: 'triangle',
                            rotation: 0
                        };
                    }
                }
            }
        }
    }
});

Tooltip Item Context

The tooltip items passed to the tooltip callbacks implement the following interface.

{
    // The chart the tooltip is being shown on
    chart: Chart
    // Label for the tooltip
    label: string,
    // Parsed data values for the given `dataIndex` and `datasetIndex`
    parsed: object,
    // Raw data values for the given `dataIndex` and `datasetIndex`
    raw: object,
    // Formatted value for the tooltip
    formattedValue: string,
    // The dataset the item comes from
    dataset: object
    // Index of the dataset the item comes from
    datasetIndex: number,
    // Index of this data item in the dataset
    dataIndex: number,
    // The chart element (point, arc, bar, etc.) for this tooltip item
    element: Element,
}

External (Custom) Tooltips

External tooltips allow you to hook into the tooltip rendering process so that you can render the tooltip in your own custom way. Generally this is used to create an HTML tooltip instead of an on-canvas tooltip. The external option takes a function which is passed a context parameter containing the chart and tooltip. You can enable external tooltips in the global or chart configuration like so:

var myPieChart = new Chart(ctx, {
    type: 'pie',
    data: data,
    options: {
        plugins: {
            tooltip: {
                // Disable the on-canvas tooltip
                enabled: false,
                external: function(context) {
                    // Tooltip Element
                    var tooltipEl = document.getElementById('chartjs-tooltip');
                    // Create element on first render
                    if (!tooltipEl) {
                        tooltipEl = document.createElement('div');
                        tooltipEl.id = 'chartjs-tooltip';
                        tooltipEl.innerHTML = '<table></table>';
                        document.body.appendChild(tooltipEl);
                    }
                    // Hide if no tooltip
                    var tooltipModel = context.tooltip;
                    if (tooltipModel.opacity === 0) {
                        tooltipEl.style.opacity = 0;
                        return;
                    }
                    // Set caret Position
                    tooltipEl.classList.remove('above', 'below', 'no-transform');
                    if (tooltipModel.yAlign) {
                        tooltipEl.classList.add(tooltipModel.yAlign);
                    } else {
                        tooltipEl.classList.add('no-transform');
                    }
                    function getBody(bodyItem) {
                        return bodyItem.lines;
                    }
                    // Set Text
                    if (tooltipModel.body) {
                        var titleLines = tooltipModel.title || [];
                        var bodyLines = tooltipModel.body.map(getBody);
                        var innerHtml = '<thead>';
                        titleLines.forEach(function(title) {
                            innerHtml += '<tr><th>' + title + '</th></tr>';
                        });
                        innerHtml += '</thead><tbody>';
                        bodyLines.forEach(function(body, i) {
                            var colors = tooltipModel.labelColors[i];
                            var style = 'background:' + colors.backgroundColor;
                            style += '; border-color:' + colors.borderColor;
                            style += '; border-width: 2px';
                            var span = '<span style="' + style + '"></span>';
                            innerHtml += '<tr><td>' + span + body + '</td></tr>';
                        });
                        innerHtml += '</tbody>';
                        var tableRoot = tooltipEl.querySelector('table');
                        tableRoot.innerHTML = innerHtml;
                    }
                    var position = context.chart.canvas.getBoundingClientRect();
                    var bodyFont = Chart.helpers.toFont(tooltipModel.options.bodyFont);
                    // Display, position, and set styles for font
                    tooltipEl.style.opacity = 1;
                    tooltipEl.style.position = 'absolute';
                    tooltipEl.style.left = position.left + window.pageXOffset + tooltipModel.caretX + 'px';
                    tooltipEl.style.top = position.top + window.pageYOffset + tooltipModel.caretY + 'px';
                    tooltipEl.style.font = bodyFont.string;
                    tooltipEl.style.padding = tooltipModel.padding + 'px ' + tooltipModel.padding + 'px';
                    tooltipEl.style.pointerEvents = 'none';
                }
            }
        }
    }
});

See samples (opens new window) for examples on how to get started with external tooltips.

Tooltip Model

The tooltip model contains parameters that can be used to render the tooltip.

{
    // The items that we are rendering in the tooltip. See Tooltip Item Interface section
    dataPoints: TooltipItem[],
    // Positioning
    xAlign: string,
    yAlign: string,
    // X and Y properties are the top left of the tooltip
    x: number,
    y: number,
    width: number,
    height: number,
    // Where the tooltip points to
    caretX: number,
    caretY: number,
    // Body
    // The body lines that need to be rendered
    // Each object contains 3 parameters
    // before: string[] // lines of text before the line with the color square
    // lines: string[], // lines of text to render as the main item with color square
    // after: string[], // lines of text to render after the main lines
    body: object[],
    // lines of text that appear after the title but before the body
    beforeBody: string[],
    // line of text that appear after the body and before the footer
    afterBody: string[],
    // Title
    // lines of text that form the title
    title: string[],
    // Footer
    // lines of text that form the footer
    footer: string[],
    // colors to render for each item in body[]. This is the color of the squares in the tooltip
    labelColors: Color[],
    labelTextColors: Color[],
    // 0 opacity is a hidden tooltip
    opacity: number,
    // tooltip options
    options : Object
}