Mt. Gox
The exchange that handled most of the world's bitcoin trading collapsed in 2014, losing about 850,000 coins. Creditors waited more than ten years.
Mt. Gox began as a site for trading collectible game cards — the name is an acronym of its original purpose — and was repurposed into a bitcoin exchange. By 2013 it handled the large majority of global trading volume.
The collapse
That was approximately 750,000 belonging to customers and 100,000 belonging to the company — roughly 7% of all bitcoin then in existence. About 200,000 were subsequently located in an old wallet. The remainder has never been recovered.
The losses were later attributed largely to theft that had been occurring gradually over a period of years, undetected, while the exchange continued to operate and to report customer balances as though the assets were present.
The aftermath
- A Japanese insolvency process ran for more than a decade. Distributions to creditors began in 2024, ten years after the filing.
- Because creditors' claims were valued in currency terms at the time of the bankruptcy while the recovered assets were bitcoin, the process produced outcomes that remain contested.
- The exchange's chief executive faced charges in Japan; the outcome did not return the missing assets.
What it demonstrated
Not a single rule of Bitcoin failed. Blocks were produced normally throughout. What failed was an unregulated company holding a great deal of other people's property with inadequate controls, no independent verification of its holdings, and no obligation to demonstrate solvency. This is the central lesson of the episode and it is about institutions, not technology.
Why it keeps being relevant
The phrase "not your keys, not your coins" entered general use because of this event. So did the practice of withdrawing to self-custody rather than leaving balances on an exchange.
And the pattern recurred. The failures of 2022 involved the same structure — customer assets held by a company, used or lost without customers' knowledge, discovered only when withdrawals were requested at scale. Eight years and a great deal of growth had not changed the underlying arrangement.
The structural gap it exposed
An exchange can publish any balance it likes. Verifying that a custodian holds what it claims requires either regulation with enforced segregation and audit, or cryptographic proof. Neither existed in 2014. Proof-of-reserve practices emerged much later and remain partial — see exchanges.