Arbitrum replaces Timeboost with per-transaction priority auctions

Arbitrum One has ditched its Timeboost transaction ordering system in favor of Priority Gas Auctions, a model that lets users compete for execution priority on every single transaction rather than winning broad time-based slots. The change went live on September 24, marking the end of a system that had only been running since April 2025. Alongside PGA, the network is rolling out Fast Feed, a paid WebSocket service that gives subscribers access to ordered transaction data before it hits the standard sequencer feed. How Priority Gas Auctions actually work Under the old Timeboost model, users participated in sealed-bid, second-price auctions to secure priority over a chunk of time. PGA flips the script. Instead of buying a time window, users set a maxPriorityFeePerGas value on individual transactions. These bids are evaluated in rapid-fire 125-millisecond rounds that fit inside 250-millisecond blocks. The system also includes what Arbitrum calls an “anti-starvation mechanism.” In plain terms, transactions with low or zero tips don’t get permanently stuck at the back of the line. The mechanism ensures they eventually get processed. Fast Feed: paying for speed, not for power Fast Feed i...