Can I use the Fonts app without paying?

Yes, you can! A limited set of fonts is available to use for free. 

And if you're curious to experience Fonts’ full potential without limits, you can easily start a one-time free trial.

Once the trial is over, it’s your choice whether to continue with a subscription to Fonts or to cancel your plan and return to the free version. To avoid unwanted charges, remember to cancel the automatic subscription no less than 24 hours prior to the end of your free trial.

For more on this topic, see What happens if I don’t want to continue with a subscription after my free trial?