Append the parameter freeAmount with the desired amount to the checkout URL. When the page opens, the shopping cart will be automatically filled with this donation amount.
The link always follows the logic
| www.startnext.com/ | projectlink/ | support | ?freeAmount= | 50 |
| Startnext | Your own link caption | Checkout | Parameters (GET) | The desired amount |
Compound Example
https://www.startnext.com/projektlink/unterstuetzen?freeAmount=50