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Bitcoin Gold (BTG)

   
Year 2017
Type Hard fork (permanent chain split)
Status Active (separate chain)

What it does

Bitcoin Gold changed Bitcoin’s proof-of-work algorithm from SHA-256 to Equihash, with the goal of making mining accessible to GPU miners rather than requiring specialized ASIC hardware.

Why it happened

By 2017, Bitcoin mining was dominated by ASIC manufacturers (primarily Bitmain). Bitcoin Gold’s creators argued this centralized mining power and that a GPU-mineable algorithm would restore decentralization.

Key details

  • Forked at block 491,407 (October 24, 2017)
  • Changed PoW from SHA-256 to Equihash
  • All Bitcoin holders at the fork received equal BTG
  • Suffered a major 51% attack in May 2018, with over $18 million in double-spends
  • Suffered a second 51% attack in January 2020

Outcome

Permanent chain split with minimal adoption. The 51% attacks demonstrated the security risks of switching to a less established mining algorithm with lower total hashrate. Market value is a tiny fraction of Bitcoin’s.