Hello @Helina !
Yes you can give free shipping based on weight. Follow these steps:
From your Shopify admin, go to Settings > Shipping and delivery.
Next to the shipping profile where you want to add a free shipping rate, click Manage rates.
Add the shipping rate to each shipping zone where you want the free shipping rate:
Click Add rate.
Enter the name for the rate.
Make sure that the value of the Price field is 0.
Click Add conditions.
Select Based on item weight.
Enter a minimum weight.
Hope this helps!
As @DigitalArtisans has mentioned, you can easily offer free shipping based on weight. Please follow this guide for the same: https://help.shopify.com/en/manual/shipping/understanding-shipping/shipping-rates#flat-shipping-rate....
To set up free shipping over a set weight, you can follow these steps below:
Step 1: Go to Shipping
Step 2: Choose one shipping zone
Step 3: Weight based rates
Step 4: Enter the name of the rate
Step 5: Type the values
Step 6: Select the price of the rate
Step 7: Click Done
For the details, you can read here.