Laurent,

CanvasJS Chart automatically sets the height and width of the chart according to container’s dimensions. If the values are not set for the container, it takes the default values. If you are using Bootstrap tabs, the issue may be that since the second tab is not displayed initially, the chart takes the default values. To solve this issue, second chart should be re-rendered when the shown.bs.tab event is fired by bootstrap.

You can also refer to this article to read up more about how to fix the issue.

—
Ananya Deka
Team CanvasJS