A swap confirmation can look identical whether you are sending a transaction yourself or signing a message for someone else to settle later. The fee, the wait, and who is stuck if the fill misses are different, which is how two screens that both say swap can leave you with different leftovers.
What goes wrong is ordinary: you signed what looked like a quote, then watched your tokens sit while someone else was supposed to post, or you paid gas for a call that reverted. People treat those two leftovers as the same market, then wonder why the explorer from-address is a stranger.
Automated market makers keep the other side as two balances in a pair, while intent auctions keep the other side as a competing filler who posts settlement. Both still exchange one token for another at a price, and how AMMs work is the pool side of that split.
UniswapX is the intent auction Labs rolled out as an opt-in beta on July 17, 2023, and a pool swap is a call against reserves already sitting in a pair. Who takes fill risk, and who posts the onchain transaction, is what splits them, even when the same UNI later sits in the same wallet.
Who posts the onchain transaction
On a pool swap you broadcast the transaction that hits the pair, and on UniswapX you sign an order while a filler later posts the settlement. The chain still records a fill, while the person who paid that fill's gas is a different party.
You want UNI for 500 USDC from a wallet you control, so on the pool path you review a swap, sign a transaction, and your wallet is the one that sends it. On UniswapX you review a floor and a deadline, then sign a message, and someone else, a filler, is the party who later submits the settlement call. A filler is a specialized participant who watches signed orders and tries to settle them.
Labs dated that split when the auction went live as an opt-in beta on the Uniswap Labs interface, available for Ethereum Mainnet. With UniswapX, swappers sign a unique offchain order, which is then submitted onchain by fillers who pay gas on swappers' behalf (source: Uniswap Blog, Introducing the UniswapX Protocol).
The chain still needs a broadcast, because transactions that change the state of the Ethereum Virtual Machine (EVM) need to be broadcast to the whole network (source: ethereum.org, Transactions). On the pool path that broadcast is your swap, and on UniswapX that broadcast is the filler's settlement. How Ethereum works is the generic fee picture, and a BloFin book fill skips both of those calls.
Suppose you sign the UniswapX order and then watch the wallet: the 500 USDC can still sit there while you wait. A confirmed reactor call is the fill, and a deadline with no reactor event is a miss. If the app instead asked you to confirm a pair transaction, you are already on the pool path, and you are the one posting it.
Hold on to one thing: look at who sent the explorer transaction, because if the from-address is yours, you posted a pool-style call, and if the from-address is a filler, you signed an intent and waited.
Fill risk when a swap misses
Fill risk is who is stuck if the swap stays unfilled. On a pool, you already sent a call, so a revert still burned your gas, and on UniswapX the filler posts, so a miss or an expiry leaves your tokens in the wallet until a later fill.
On the pool path the risk is easy to miss because the review screen looks like a quote, and it is a bound for that one call. If the reserves move past the floor you typed, the swap fails, and you still paid network fees for the attempt. That revert bound is the same family of limit as what slippage is.
On UniswapX the signed floor is the bound the reactor will check. If nobody can meet it before the deadline, the signature dies, and the 500 USDC never left for a failed filler transaction. The docs put the failed-fill cost on the filler: gas fees are wrapped into the final price and are paid by the filler, and failed swaps do not incur any fees at all (source: Uniswap Docs, Auction types).
That claim is about the settlement post. A first spend grant can still need gas, because that approve is your transaction, and wrapping a native token so it can be sold can still need gas. Those setup calls are yours, and they sit beside the fill. If the fill fails, the filler's failed gas stays with the filler, while you can still have spent gas earlier.
Read the two misses the same way: a reverted pool swap is your failed call, an UniswapX expiry with no filler transaction is a signature that went stale, and an UniswapX fill that reverts is a filler's failed settlement. In the last two cases the 500 USDC should still be in the wallet unless a pull already ran, so check the token balance, rather than only the quote screenshot.
What matters here is the person who had something at risk when the fill stayed open: on the pool it was your gas for that call, and on UniswapX it was the filler's gas for the post, while you waited on a signature.
How an intent executes beside a pool
An UniswapX order is a signed intent: what should come out, and a floor the reactor can check, while a pool swap is a call that moves two reserves. Those are two execution designs, even when both later show UNI in the same wallet.
The repo names the UniswapX unit as a signed order. Swappers generate signed orders which specify the specification of their swap, and fillers compete using arbitrary fill strategies to satisfy these orders (source: Uniswap, UniswapX README). The filler's strategy is the filler's work, and your part is the floor and the deadline on the review screen.
The pool path is the other design: when a user swaps one token for another, they trade against the pool's reserves (source: Uniswap Docs, How Uniswap Works). How that product is kept, including a toy size versus a thin pool, sits in how Uniswap works, and the constant-product walk lives there. The tell is simpler: the other side is inventory already in the pair.
Uniswap governance has already said the auction sits beside the AMM rather than replacing it. The X protocol is complementary, and it solves problems the AMM leaves open (source: Uniswap Governance, UniswapX and the DAO). The hub on what Uniswap is named UniswapX as a separate path from the live pool versions. v2 is still the constant-product pool with fungible LP shares, which is Uniswap v2.
You can skip filler vocabulary and still read the two screens, because if the wallet asks you to send a swap transaction, you are executing against a pool, and if it asks you to sign an order and wait, you are executing an intent. UNI in the wallet after either path is the same vote token, and the explorer record is what names the market.
Shared settlement, different posters
A UniswapX fill and a pool fill still have to move tokens, name a price, and leave an explorer record, and they share that work even while they store the other side in different places. The table here describes those parts as a description of how each fill is built.
Both still exchange one token for another at a price, while the pool stores the other side as two reserves and UniswapX stores the other side as a competing filler, who may use private inventory or a pool behind the scenes. Labs groups UniswapX with aggregators because aggregators like UniswapX look across many liquidity sources at once, rather than relying on a single token pool (source: Uniswap Blog, What is a Decentralized Exchange (DEX)?).
That is a type split, so a pool is still the right fill when you wanted to trade against inventory you can see in a pair, and UniswapX is the right fill when you wanted to sign a floor and let someone else post. Order books are a third design, and that comparison sits in Uniswap AMM versus order books, while the remaining split is the auction versus the pair.
| Criterion | Pool swap | UniswapX |
|---|---|---|
| What you sign | A swap transaction | An offchain order |
| Who posts the fill | You | A filler |
| Who sets the fill | Pool reserves | First successful filler |
| If the fill misses | You paid that gas | The filler paid that gas |
| Other side | The pair's two tokens | Filler inventory or other venues |
That table is a description rather than a score.
A confirmation still has to match the market you used: a pool fill shows a swap against a pair, and an UniswapX fill shows a reactor settlement. UNI can land in the same wallet from either path, so the explorer record is the tell, and a later UNI balance is a poor proof of which design ran.
The idea to carry forward is shared settlement, different posters. The next split is what happens when the filler's inventory is, in fact, a Uniswap pool.
When a filler still uses a Uniswap pool
A filler can still source the output from a Uniswap pool, and that leaves UniswapX as an intent auction rather than turning it into a pool swap. You signed an intent, the filler posted the settlement, and the pool, if it was used, was the filler's inventory, rather than your transaction.
Labs' own walk makes that route explicit: a filler could fill a signed order using private inventory of the output token, or by routing the input to a variety of onchain liquidity venues such as the Uniswap Protocol or Sushiswap (source: Uniswap Labs support, How does UniswapX work?). The deciding fact is the or: private inventory or a protocol pool.
So both facts can be true at once: UniswapX sits beside the AMM, and a Uniswap pool can still move because a filler used it. You should read who signed the intent, then who sent the settlement. A pair event on an explorer is a poor proof that you posted a pool swap. If you wanted the pair you can see, you wanted the pool path, including the two reserves in Uniswap liquidity pools.
v4 leaves that split in place as well. Extra code a pool can run at set points is a hook, and depth on that design sits in Uniswap v4 and hooks. A filler can still use a hooked pool as inventory, and the hook leaves you as the signer of the UniswapX fill.
If the interface skipped UniswapX and asked you to confirm a pair call, there is no filler in the middle, which is the pool path again. The next section is only how to pick before you sign.
Which path fits which swap
Which path fits depends on the purpose: a pair you wanted to call yourself, or a signed floor you wanted someone else to settle. There is no single winner between UniswapX and a Uniswap pool, so you pick the design that matches the confirmation you want.
Pick the pool path when you want the inventory you can see, pay the gas token for that call, and accept that a revert still costs you fees. Pick UniswapX when you want to sign a floor, skip posting the settlement, and wait for a filler, or for the signature to go stale. If the app never offered UniswapX, you are staying on an AMM route, because some sizes and some chains stay on AMM routes.
BloFin has listed UNI/USDT on spot since January 15, 2024. A UNI/USDT fill is a venue book, separate from an UniswapX reactor event and separate from a Uniswap pair swap.
Check four things before you treat a screen as UniswapX:
- The wallet asks for an order signature, rather than a swap transaction you broadcast.
- A floor and a deadline are on the review, rather than only a pair ratio.
- After confirm, the explorer from-address is a filler, rather than you.
- A spend grant for that input token is a later approve. The grant walk sits with Uniswap wallet and self-custody.
If you needed the pool, you wanted reserves, your own broadcast, and your own revert gas; if you needed UniswapX, you wanted a signed floor and a filler who posts; and if you needed a venue credit, you wanted UNI/USDT.
Common questions about UniswapX vs pool swaps
If my swap is under 300 USDC equivalent, did UniswapX skip me?
Often the interface will stay on an AMM route. The API includes UniswapX in routing when the order is worth more than 300 USDC equivalent, or when the UniswapX quote improves on the AMM route by at least 0.2 percent (source: Uniswap Docs, AMM vs UniswapX routing). At or under that 300 USDC mark, UniswapX only joins when that 0.2 percent improvement is there. A pool fill at that size is still a real fill, and it is a size-and-quote routing choice.
If BloFin already filled UNI/USDT, did UniswapX settle?
BloFin matches UNI/USDT on its own book. Closing that fill leaves an UniswapX order on its own deadline, and it leaves a Uniswap pair untouched, because they skip a shared matching engine. If you meant only the onchain intent, cancel the working venue order yourself, watch each screen until one is flat, and leave the UniswapX deadline on its own timer.
If the exclusive filler fades, did my USDC already leave?
Fade means the winning quoter skipped settling before the exclusive window ended. Your tokens stay in the wallet until a later filler posts, or until the deadline passes with no fill. The open auction after a fade is still UniswapX. Check the token balance, because a stale signature is still a signature.
Is UniswapX a newer pool version than Uniswap v4?
v2, v3, and v4 are live AMM designs with LP shares, and UniswapX has no LP shares, so that split leaves UniswapX beside those versions. If you wanted hooked pool behavior, you wanted a v4 pair. If you wanted a signed floor, you wanted UniswapX. A v4 pair event after an UniswapX wait can still be the filler's inventory.
If I revoke Permit2 after I already signed an UniswapX order, can a filler still pull?
A filler can pull only until the grant is actually closed onchain. Revoke is a later transaction you post, and it costs gas. A filler who already settled before that revoke can keep the fill, and a filler who arrives after the revoke should fail the pull. Check a revoke tool for an open grant on that token, then check the UniswapX deadline, because the grant is separate from the auction.
If the quote I signed and the UNI that landed are different, did I get the wrong fill?
A gap between the first quote and the landed amount is ordinary on UniswapX, because the auction can start at a better output and move toward the worse bound you already signed, so the landed amount can sit between those two numbers. The wrong fill is an output below the minimum, or a pool swap you did not mean to send. Read the minimum on the signature, then the reactor confirmation, and compare those two numbers on the signed order.
If the Uniswap app routed me to a v2 pool, did I still use UniswapX?
A v2 pool call is a swap against that pair's reserves, and you post it, while UniswapX is the signed order a filler posts. The app can pick the pool when UniswapX is ineligible, which is a pool fill. Match the wallet prompt, transaction versus order, and if you already paid gas for that pair call, you were on the pool path.
Researched and written by the BloFin Academy editorial team with AI-assisted drafting. Updated September 2026. Primary sources include Introducing the UniswapX Protocol, Uniswap's AMM vs UniswapX routing docs, the UniswapX README, How Uniswap Works, Auction types, Labs' How does UniswapX work, UniswapX and the DAO, the DEX explainer, ethereum.org transactions, and BloFin's public spot instrument endpoint. All facts independently verified against cited documentation current as of September 2026.
This article is educational and general in nature, not financial or investment advice. Cryptocurrencies like UNI carry real risks, including price volatility, smart-contract risk in pools and hooks, venue risk on an exchange balance, failed or expired fills, and the chance of losing funds to a fake token or a thin pool. Nothing here is a recommendation to buy, sell, hold, or participate in any project. Do your own research, and consider speaking with a licensed professional before making financial decisions. BloFin does not provide investment advice.