Mt. Gox was a defunct Tokyo custodial exchange led by Mark Karpelès. Its collapse combined a long-running theft of bitcoin, weak wallet and accounting controls, frozen withdrawals, and an insolvency and rehabilitation process lasting more than a decade. It was a failure of a centralized custodian, not of Bitcoin consensus.
Mt. Gox began as a domain Jed McCaleb intended for trading Magic: The Gathering cards, then became a Bitcoin exchange in 2010. French programmer Mark Karpelès took it over in 2011, and the small experiment became the dominant gateway to the early Bitcoin market. Growth outran internal control: a customer saw a number in an account while one company controlled the actual coins and keys. [1]
The crisis peaked in February 2014. Mt. Gox first stopped BTC withdrawals, later halted all trading, and applied for civil rehabilitation in Tokyo on 28 February. It reported that its records showed approximately 750000 BTC belonging to customers and 100000 BTC belonging to the company missing, about 850000 BTC in total. Those figures were a balance-sheet estimate at collapse, not a final forensic finding of one theft. [2]
The exchange initially pointed to transaction malleability, a known property that can change the identifier of an otherwise equivalent transaction before confirmation. Bitcoin.org explained that the protocol itself required no emergency repair and that the problem mainly affected services with faulty internal accounting. Malleability could confuse a badly written system, but later analyses do not support the claim that it explains the whole Mt. Gox deficit. [3]
In March 2014, while rescanning an old wallet used before June 2011, the company found 199999.99 BTC, rounded to 200000 BTC. The estimate of missing coins therefore fell from 850000 BTC to approximately 650000 BTC. Finding funds in a wallet management considered empty was itself evidence of a deep failure in inventory, system separation, and the company’s ability to determine its own reserves. [4]
WizSec’s independent analysis concluded that most of the deficit accumulated gradually after wallets were compromised in 2011, rather than in a single event in February 2014. In 2023 the US Department of Justice charged Alexey Bilyuchenko and Aleksandr Verner with breaking into the Mt. Gox server and laundering approximately 647000 BTC. A charge is a prosecutor’s allegation, not by itself a final judgment about every missing coin. [5]
After the first rehabilitation attempt was rejected, the company entered bankruptcy in April 2014. On 22 June 2018 the Tokyo court opened civil rehabilitation under trustee Nobuaki Kobayashi. The change mattered to creditors: their bitcoin claims were no longer treated only as yen claims valued at the time of the old bankruptcy, and the plan could distribute part of the preserved BTC and Bitcoin Cash. [6]
A large majority of voting creditors approved the rehabilitation plan, and the Tokyo District Court confirmed it on 20 October 2021; it became final and binding on 16 November 2021. That did not promise every creditor the original bitcoin balance one for one. The amount and form of repayment depend on the allowed claim, selected option, available estate, sales of some assets, and the plan’s rules. [7]
On 5 July 2024 the trustee announced the first repayments in BTC and Bitcoin Cash to some creditors through designated exchanges. The process did not end there: the official site later moved the deadline for base, early lump-sum, and intermediate repayments to 31 October 2026. The case teaches two separate lessons: proof of reserves without a full view of liabilities is insufficient, and a balance at a custodial exchange is not self-custody unless the user controls the private keys. [8]
For the clearest picture, read this entry together with Custodial Exchange, Counterparty risk, Proof of reserves, Self-custody, Private Key, Cold Storage. The reverse links also lead from FTX Collapse.
01Did a flaw in the Bitcoin protocol cause the collapse of Mt. Gox?+
No. Transaction malleability was a real, known property that could confuse poorly designed service accounting, but it did not let anyone spend other people’s coins without a signature. Available forensic and official sources point to long-running wallet compromise, inadequate key separation, accounting discrepancies, and late discovery of the deficit at a centralized exchange.
02Did creditors recover all 850000 BTC?+
No. After approximately 200000 BTC were found, the estimated deficit remained about 650000 BTC, and the available estate cannot return original balances one for one. Rehabilitation distributes allowed claims in different forms under the plan; repayments began in 2024, and the official deadline for part of the process was moved to 31 October 2026.