When you send Bitcoin, Ether or SOL, the transaction shows up almost immediately. That doesn’t mean it is permanent. Every blockchain has a point after which a transaction can no longer be reversed, called finality, and the time it takes to get there ranges from under a second to around an hour depending on the network. Solana’s Alpenglow upgrade this week cut its finality time from about 12.8 seconds to a target of roughly 150 milliseconds, which makes this a good moment to explain what finality is and why traders should care.What finality meansA blockchain is a shared record kept by thousands of computers that must agree on which transactions happened and in what order. Agreement takes time. Until enough of the network has signed off, there is a small chance a transaction could be dropped or replaced if part of the network had a different view of events.Finality is the point where that chance is gone, or so small it can be ignored. Before it, a transaction is pending, however confident the screen looks. After it, the transaction is settled.Bitcoin: finality by accumulationBitcoin never declares a transaction final. Instead, each new block added on top makes it harder to reverse, because rewriting history would mean redoing all the computing work in those later blocks. New blocks arrive about every 10 minutes on average.This is called probabilistic finality. The longer you wait, the safer the transaction becomes. A common convention is to wait for six confirmations, roughly an hour, before treating a large payment as settled, though many exchanges credit deposits after fewer. The trade-off is clear: Bitcoin is slow to settle, but reversing a transaction buried under several blocks would require enormous computing power.Ethereum: finality by checkpointSince its move to proof-of-stake, Ethereum has had a definite finality point. Validators, who lock up ETH to take part, vote on checkpoints. Once two-thirds of staked ETH has backed a checkpoint in two consecutive rounds, everything before it is finalized. Reversing a finalized block would mean a large share of validators losing their staked ETH.In practice that takes about 15 minutes, according to ethereum.org. In a pleasing coincidence, the theoretical minimum is 12.8 minutes, the same figure as Solana’s old finality time, just in minutes rather than seconds. Faster finality is on Ethereum’s research roadmap, but there is no confirmed date.Solana: finality in a fraction of a secondSolana also uses staked validators, but it is designed for speed. Under its previous system, TowerBFT, transactions were quickly marked “confirmed”, but full finality took about 12.8 seconds. Alpenglow, live on mainnet since 21 October, merges those stages into one and targets finality of about 150 milliseconds. Early dashboard readings have been somewhat above that target, so the real-world figure is worth watching as the network beds in. Why traders should careFinality affects how quickly you can use your money. Exchanges usually wait for a transaction to settle before crediting a deposit, so slower finality means a longer wait before funds can be traded. For anyone moving coins between exchanges to take advantage of a price difference, that delay is a real cost, because the opportunity can disappear while the transfer settles.It also matters for payments and decentralised finance. A merchant or lending app that acts on a transaction before it is final takes on a small risk that it gets reversed. Faster finality shrinks that window.Speed is not the same as qualityIt is tempting to read finality times as a league table, with Solana top and Bitcoin bottom. That misses the trade-offs. Bitcoin’s slower process is part of what makes its history so hard to rewrite. Ethereum’s longer window comes with a very large, widely distributed validator set. Solana’s speed relies on high-performance validators, and the network has a history of outages, so its new system still has to prove itself under real conditions over time.The right question is not which network is fastest, but whether its settlement speed and security suit what you are doing. An hour is fine for moving savings into cold storage. It is not fine for a shop counter.What to watch nextExchange deposit times for SOL. If major exchanges cut their waiting periods, Alpenglow’s speed is reaching users.Solana’s live finality. Watch whether it settles near the 150 millisecond target under heavy load.Ethereum’s roadmap. Any firm timeline for faster finality would narrow the gap with faster networks.Your own exchange’s policy. Check how many confirmations it needs for each coin before you move funds in a hurry.The practical takeaway: a transaction on screen is not the same as a settled one. Knowing how long finality takes on each network tells you how long your money is really in transit. This article was written by Eamonn Sheridan at investinglive.com.