Is Ethereum's Uptime really 100%? How is this defined? In fact, in Ethereum Devcon 2 (Shanghai) 9 years ago, the Ethereum network suffered a DDOS attack, known as the "Shanghai Attack". But the advantage of blockchain is that all data is stored on the chain, making it easy to verify. Alternatively, a lot of data can be obtained through third-party platforms such as Etherscan. Firstly, it is important to understand that blockchain networks do not have a physical concept of 'time'. The smallest unit of time is a block (or more accurately, a slot), which is approximately 12 seconds on average for Ethereum. Also, before Ethereum switched from PoW to PoS, the proof of work mechanism did not have a stable block time due to its randomness. So even with the current BTC network, sometimes it's normal for the card to remain inactive for a long time. I checked the block data during the Shanghai Attack period (approximately in the range of 2283000 to 2301000) and found a large number of cases where the block generation time far exceeded the average of 12 seconds. Until this issue is completely fixed, the network will intermittently experience slow block generation. Found a few of the most serious ones (only searched a portion of the data, the actual situation may be even worse): Height 2283421: Block time of 181 seconds, equivalent to 15 times the average value. Height 2283446: Block time 136 seconds, equivalent to 11 times the average value. There is still a difference in user experience when a transaction that used to take ten seconds turns into a few minutes. However, 9 years ago on Ethereum, the user base was still very small, so there was nothing to worry about. We won't delve into the specific technical issues that led to the DDOS attack. In order to fix this problem, two hard fork upgrades were conducted, codenamed Tangerine Whistle and Spurious Dragon. Compared to AWS or Cloudflare, which experience downtime that lasts for tens of minutes or even hours, the worst-case scenario for the Ethereum network is only a few minutes of fluctuations (if there are even worse situations, please feel free to provide additional data). Ethereum's Uptime may not be strictly 100%, but a decentralized network that can withstand the "Shanghai Attack" is far more trustworthy than a centralized system that has never been down.