When you start a bitcoin node, you have an option called pruning with a mb (or gb) limit. We know that it allows to free up space, but, how is it made ?

Deleting blocks
For freeing space, there isn't 1k solutions, and the most efficient is... deleting things, and it is exactly what pruning do. It will keep the last 500 mb (for example) of blockchain and delete all blocks that are before.

But... how is it secured ?

If we delete blocks, we cannot check their validity, so for that, it will use another good thing called merkle tree.

Then, we only have to keep useful branches (containing hashes of txns involving your account, for example)

Impacts on use

Good :

• Disk space saved
• Lowered node sync time

Bad :

• Doesn't help the network (doesn't seed all the blockchain)
• Unable to run a LN node (it needs for non-pruned bitcoin node)

It is the end of this (short) explanation. I hope that you learned something in.

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And if you see smth to add or improve, feel free of saying it in the comments !