Solana’s Alpenglow upgrade has reached the public developer network, giving application teams a chance to test a new consensus system designed to reduce transaction finality from about 12.8 seconds to around 150 milliseconds.
Alpenglow is now active on Solana’s devnet and testnet, but it has not yet been activated on mainnet. Anza, the company developing Solana’s validator software, announced the devnet rollout on Sept. 25, one day after the upgrade moved to testnet.
Devnet allows developers to test their applications using tokens with no real value, while testnet gives validators and infrastructure providers a more demanding environment to test the new software.
For now, Solana’s mainnet still uses the existing TowerBFT consensus system. This means the 150-millisecond finality figure is still a target for Alpenglow and is not the finality speed users currently get on the live network.
Under the current system, validators submit their votes as transactions that are included in blocks. A block generally needs votes across 32 slots before it becomes final, which takes about 12.8 seconds.
Alpenglow changes this process. Its first phase, called Votor, allows validators to send votes directly to each other instead of recording those votes as regular onchain transactions.
According to the Solana Foundation, a block could become final after a single voting round if validators representing at least 80% of the network’s stake approve it. A second voting round provides another way to reach finality when the first round does not meet the required threshold.
Faster finality could be useful for exchanges, payment companies and other businesses that need to know when a Solana transaction can no longer be reversed. However, each company can still set its own requirements before crediting deposits or completing payments.
Alpenglow also differs from Solana’s recent changes to block production speed. Solana recently reduced its target slot time from 300 milliseconds to 250 milliseconds, with another reduction to 200 milliseconds planned separately. Shorter slots mean blocks can be produced more frequently, while Alpenglow focuses on how quickly the network confirms those blocks as final.
Most applications that simply send transactions and read account balances will not need major changes because of Alpenglow. The transaction process, fees and basic account operations remain the same.
However, services that collect and organize blockchain data will need to make adjustments.
Alpenglow can produce multiple candidate blocks for the same slot before the network decides which one should be confirmed. Data providers will need to keep these candidates separate and only include the confirmed block in their final records.
Validator votes will also no longer appear as normal transactions inside blocks. This means blockchain explorers and analytics platforms that count validator votes as transactions could show lower transaction totals after Alpenglow is activated, even if users continue making the same number of transactions.
Some services currently use validator vote transactions to track network participation. Under Alpenglow, that information will instead be provided through certificates connected to block data.
Services using Solana’s Geyser or gRPC data streams will also need to handle identifiers that separate different candidate blocks within the same slot.
Alpenglow’s mainnet launch still does not have a confirmed date. An earlier roadmap pointed to an October target, but the move to testnet and devnet does not guarantee a specific mainnet activation date.
Anza’s current software schedule allows mainnet feature activations to resume on Sept. 28, but that date has not been announced as the Alpenglow launch date.
The Solana Foundation describes Votor as the first phase of the upgrade. A later phase called Rotor is expected to change how blocks are distributed across the network.
For now, developers are testing the new voting and finality system on devnet and testnet, while the roughly 150-millisecond finality target remains something to be tested before it reaches Solana’s live mainnet.
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