You are right in saying nodes nowadays do not enforce the original ordering meaning given to the `nSequence` field, though note this was never implemented as part of block validation (couldn't have been). This was indeed "disabled" but was not a change to the consensus rules. We can say it was only "policy". However this field was also attached a consensus meaning early on. On October 29th 2009 Satoshi (in commit [`cc0b4c3b62367a2aebe5fc1f4d0ed4b97e9c2ac9`][1]) made the `IsFinal()` function consensus critical. This introduced absolute timelock capability through the `nLockTime` transaction field, which is disabled if any of the transaction inputs has an `nSequence` that is not `0xffffffff`. See also [this question][2] on this topic. Nowadays, additional meanings were given to this field. Both "policy" and consensus: - Relative timelocks. This is consensus. [BIP68 specifies][3] a way of using the first 16 bits of the `nSequence` to denote a relative locktime either in a number of blocks or as a multiple of 512 seconds. This is only possible if the transaction's `nVersion` is superior or equal to `2`. The type is determined by setting the 23rd bit (in seconds) or not (in blocks). The relative timelock may be disabled by setting the 32nd bit. - RBF. This is "policy" only. The Bitcoin Core client has been refusing unconfirmed transactions replacement if the original transaction's inputs all have their `nSequence` field set to `0xffffffff`. Even if the replacement transaction pays more fees. Note like the original ordering meaning from Satoshi, this *cannot* be enforced by consensus. And a miner would obviously be incentivized, at least in theory, to not respect this rule. See [rule #1 from this doc][4]. It's also worth mentioning the Lightning Network specifications have been (ab)using part of [the `nSequence` field in commitment transactions to store the (obscured) commitment number][5]. [1]: https://github.com/bitcoin/bitcoin/commit/cc0b4c3b62367a2aebe5fc1f4d0ed4b97e9c2ac9#diff-608d8de3fba954c50110b6d7386988f27295de845e9d7174e40095ba5efcf1bbR1221-R1226 [2]: https://bitcoin.stackexchange.com/q/90229/101498 [3]: https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki#user-content-Specification [4]: https://github.com/bitcoin/bitcoin/blob/master/doc/policy/mempool-replacements.md#current-replace-by-fee-policy [5]: https://github.com/lightning/bolts/blob/master/03-transactions.md#commitment-transaction