Zig zag border for a circle?

Question

Based on many tutorials I am able to create a zig zag border for square/rectangle objects using :after and :before. However when it comes to circle

Answer 1

Another solution is to use clip-path property:

.box {
  width: 150px;
  height: 150px;
  background: lightblue;
}

.clipped {
  clip-path: polygon(50% 0%, 46.93% 3.1%, 43.47% 0.43%, 40.83% 3.9%, 37.06% 1.7%, 34.89% 5.49%, 30.87% 3.81%, 29.21% 7.85%, 25% 6.7%, 23.89% 10.92%, 19.56% 10.33%, 19.01% 14.66%, 14.64% 14.64%, 14.66% 19.01%, 10.33% 19.56%, 10.92% 23.89%, 6.7% 25%, 7.85% 29.21%, 3.81% 30.87%, 5.49% 34.89%, 1.7% 37.06%, 3.9% 40.83%, 0.43% 43.47%, 3.1% 46.93%, 0% 50%, 3.1% 53.07%, 0.43% 56.53%, 3.9% 59.17%, 1.7% 62.94%, 5.49% 65.11%, 3.81% 69.13%, 7.85% 70.79%, 6.7% 75%, 10.92% 76.11%, 10.33% 80.44%, 14.66% 80.99%, 14.64% 85.36%, 19.01% 85.34%, 19.56% 89.67%, 23.89% 89.08%, 25% 93.3%, 29.21% 92.15%, 30.87% 96.19%, 34.89% 94.51%, 37.06% 98.3%, 40.83% 96.1%, 43.47% 99.57%, 46.93% 96.9%, 50% 100%, 53.07% 96.9%, 56.53% 99.57%, 59.17% 96.1%, 62.94% 98.3%, 65.11% 94.51%, 69.13% 96.19%, 70.79% 92.15%, 75% 93.3%, 76.11% 89.08%, 80.44% 89.67%, 80.99% 85.34%, 85.36% 85.36%, 85.34% 80.99%, 89.67% 80.44%, 89.08% 76.11%, 93.3% 75%, 92.15% 70.79%, 96.19% 69.13%, 94.51% 65.11%, 98.3% 62.94%, 96.1% 59.17%, 99.57% 56.53%, 96.9% 53.07%, 100% 50%, 96.9% 46.93%, 99.57% 43.47%, 96.1% 40.83%, 98.3% 37.06%, 94.51% 34.89%, 96.19% 30.87%, 92.15% 29.21%, 93.3% 25%, 89.08% 23.89%, 89.67% 19.56%, 85.34% 19.01%, 85.36% 14.64%, 80.99% 14.66%, 80.44% 10.33%, 76.11% 10.92%, 75% 6.7%, 70.79% 7.85%, 69.13% 3.81%, 65.11% 5.49%, 62.94% 1.7%, 59.17% 3.9%, 56.53% 0.43%, 53.07% 3.1%);
}

As mentioned in another answer - the tricky part is figuring out the right values. I didn't pick them by hand - check this codepen to see how they are generated.