Consequences of changing the theme font in existing presentation - PPT 2019

When you go to the slide master by clicking View - Slide Master and select the Fonts button in the Background group, you can effectively see which theme font is active.

Starting with a blank presentation, this is the Office theme. In the list of fonts, the Office theme is selected in gray. The Calibri Light font is active for the header and the Calibri font for the body text. This is in the PPT 2019 version, in other later versions these can be different fonts.

Below is an example of a slide with the built-in Office theme font.

If you choose a different theme font from the list in the slide master, it will have effect on all the underlying slides.

Below you see the same slide where the theme font Arial Black (header) and Arial (body) was chosen.

As you can see, all the text on the slide has been changed. Including the text in shapes, text boxes and graphs.

Also note that you do not do this with impunity, for example look at the main title which  suddenly runs over 2 lines!

Changing the theme font is not the same thing as selecting the master placeholders and applying a font.

On the sample slide below I applied Arial Black for the header and Arial Rounded MT Bold for the main text in the master placeholders. The underlying slides are all affected since the master determines the appearance of the placeholder text. Unfortunately, other text from text boxes and graphs and shapes has not. 

What if you create a completely new theme font in the slide master as in the example below?

To do this, click on the list arrow next to Fonts and select Customize font at the bottom.

Choose your fonts, in the example below I have set Arial Rounded MT Bold for the header and Brittanic Bold for the main text. Then give the theme a name and click Save.

The new theme font now also appears in the list of theme fonts under the Custom section. It is also immediately applied to all underlying slides.

What if you return to the slides and notice that the theme hasn't been applied? This is probably due to the fact that a change has been made to the slide itself. For example, you selected an object and manually adjusted the font. Since local formatting has priority, changing the theme font will do nothing.

Below is the same example where the Aptos Display font has been applied to the blue rectangle. As you can see, the theme font change had no effect.

If you still want the object to follow the theme font, you can clear the local formatting.

Select the shape and in the Font group of the Home tab, click the Clear All Formatting button.

Now the shape will follow the master theme font.