A very large share of Solana swap volume passes through Jupiter, and for good reason: its router splits orders across pools and venues to find the best execution, and it does not charge a protocol fee for doing so on standard swaps. For an ordinary user, using Jupiter rather than going directly to a pool is close to free money in the form of better fills.
What Jupiter actually does
The core is a routing engine that queries Solana's DEX liquidity — Orca, Raydium, Meteora, Lifinity and others — and constructs a path, often splitting a single trade across several pools. On top of that sit limit orders, dollar-cost-averaging, a perpetuals venue backed by the JLP pool, and a developer API used by wallets and applications across the chain. Jupiter is less a venue than Solana's exchange layer.
Costs
There is no protocol fee on standard swaps. What you pay is the underlying pool fees on whichever venues the route touches, Solana network fees measured in fractions of a cent, priority fees during congestion, and price impact. Slippage settings matter more here than on Ethereum: Solana's speed means a badly set tolerance can be exploited by sandwich bots, and Jupiter's dynamic slippage estimation exists specifically to reduce that.
The risks of aggregation
Routing through an aggregator means trusting two things: that the router is choosing honestly, and that every venue it routes into is safe. A vulnerability in an integrated pool becomes your problem for the duration of the transaction. Jupiter's contracts have not been exploited, its code is open, and it has operated at enormous volume without incident — but the surface is broader than a single-pool swap, and its governance and token distribution have been contentious within its own community.
Who should use Jupiter
Everyone trading on Solana. There is no good reason to swap directly against a single pool when the router is free and demonstrably better. Its limit orders and DCA tools are the best on the chain. Just remember that it does nothing for you anywhere else — this is Solana infrastructure, full stop.