New tech feels like it is appearing every other week in Smash 4, with the current tech du jour being Grounded Spike Cancelling or GSC for short. First discovered by Flynn CL, documented by ESAM, and now covered by the Beefy Smash Doods, this technique allows players to cancel the grounded tech animation of a spike, so you can then punish with your own move.
To cancel the spike, you have to SDI upwards as soon as you get hit by the move, before then hitting the shield button to tech the floor. If done correctly, your character should bypass the tech animation and be able to strike back very quickly. You can also SDI to the side if you are placed on a ledge or platform, meaning you can follow up with an aerial after using GSC. Do note that GSC does not apply to untechable moves like Ganondorf’s or Megaman’s down air, as well as if you are already in a knockdown state.
Much like doing a footstool out of shield, GSC is a great situational technique which can net you a decent punish off of an opponent either doing a panic on stage spike, a Samus player using up-tilt or against a Peach player spamming down-tilt, as you can pop back up and strike back against your opponent very quickly. Consider adding Grounded Spike Cancelling into your defensive repertoire.
Source: Beefy Smash Doods