What's the current situation with Bitcoin testnets?

External question — Bitcoin Stack Exchange Author: jiamijiang Original post: https://bitcoin.stackexchange.com/questions/130709 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. On mempool.space, testnet3 is marked as deprecated and encourages users to use testnet4. is testnet4 now the canonical testnet for Bitcoin? why not just call testnet4 just testnet now? it's all confusing

External answer — Bitcoin Stack Exchange Author: Pieter Wuille Original post: https://bitcoin.stackexchange.com/a/130710 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. Yes, use testnet4. Testnet3 is deprecated, but we also cannot force people to stop using it; it's still a decentralized network that will exist as long as people are using it, regardless of the wishes of developers. Testnet4 will likely never be renamed to "testnet". That would just be monumentally confusing, having the same name for two distinct networks with distinct rulesets.