Between signing and the block
When you press send, your transaction does not go into the blockchain. It goes into a queue to maybe get into the blockchain. Your wallet broadcasts the signed transaction to a node, the node checks it is valid, and then it enters the mempool — the pool of pending transactions waiting for a block producer to pick them up. Everything your wallet shows as "pending" is living in this waiting room, and most of the confusing things transactions do — stalling, disappearing, being replaced — are mempool behavior, not blockchain behavior.
What the mempool actually is
The first surprise: there is no single, global mempool. Each node keeps its own pool of pending transactions and gossips them to its peers, so the network holds thousands of largely-overlapping but never identical copies. A transaction "in the mempool" really means "in most well-connected nodes' mempools by now." Nodes also enforce local limits — minimum fees, per-account caps, eviction when the pool is full — which is why a very-low-fee transaction can quietly vanish from the network without ever failing on-chain.
How transactions leave: the fee auction
Block space is scarce, and the mempool is where the market for it clears. Block producers assemble the most profitable set of pending transactions, which in practice means fee priority decides who exits the waiting room first. On EVM chains that priority is the tip you attach under EIP-1559's base-fee-plus-tip model — pay the going rate and you leave in seconds; underbid and you wait until demand cools or your transaction is evicted.
Pending, replaced, dropped
Because a pending transaction is not yet history, it can still be edited in one specific way: replaced. Broadcasting a new transaction with the same nonce and a higher fee tells the network to forget the old one — the standard cure for a stuck send (and, with the same trick sending zero to yourself, the standard cancel). Transactions that neither confirm nor get replaced are eventually dropped: evicted from pools and forgotten, as if never sent. Nothing was lost — the funds never moved — but the invisibility of all this from a typical wallet UI is where most "where is my transaction?" panic comes from.
A very public waiting room
Everything in the public mempool is visible to anyone before it confirms — including bots that parse pending swaps and act on what they see. That visibility is the raw material of front-running and the sandwich trades we describe in our slippage explainer: your pending trade tells the world exactly what you are about to pay. As of 2026, a meaningful share of EVM transactions therefore travels through private submission channels that bypass the public pool and go straight to block builders — a trade of transparency for protection that comes with its own trust assumptions.
Not every chain has one
The classic gossip mempool is an Ethereum-style design, not a law of nature. Solana largely skips it: upcoming block producers are known in advance, so transactions are streamed directly to them rather than pooled globally — one reason its pending states feel so short-lived. TON routes messages through its own sharded pipeline rather than one shared pool. And ERC-4337 adds a parallel lane on EVM itself: UserOperations wait in an alternative mempool of their own before bundlers package them, as we unpack in bundlers and UserOperations.
How WATS fits in
The mempool is exactly the layer WATS manages so you rarely think about it: the wallet broadcasts through healthy nodes and tracks pending status across EVM, Solana and TON, three ecosystems with three different waiting rooms, behind one interface. On EVM, WATS actions travel as ERC-4337 UserOperations through the alt-mempool, where a paymaster settles the native gas — which is how every action, on every chain, is charged in one token, ATS, instead of the native coin (Solana and TON use an equivalent fee-payer/relayer). So a send never sits pending because you lacked the right gas token; the ATS fee simply tracks the live network cost. ATS is a LayerZero OFT — one balance across all three ecosystems — and collected ATS is burned from a 100M supply toward a 30M floor. WATS stays fully non-custodial — you hold your keys, WATS never holds one — and remains the first and only wallet to combine ERC-4337 and OFT single-token fees with that burn. The mechanics live on the ATS fee page.
Frequently asked questions
Is there one global mempool?
No. Every node maintains its own pool of pending transactions and shares them with peers over a gossip network, so what exists is thousands of overlapping local views rather than one master queue. That is why explorers sometimes disagree about a pending transaction, and why a very-low-fee transaction can be present in some pools, evicted from others, and eventually forgotten by all of them.
Why is my transaction stuck pending, and can I cancel it?
It is almost always waiting in the mempool because its fee is below the going rate — it will confirm if demand cools, or wait indefinitely. Because a pending transaction can be replaced, the fix is to rebroadcast with the same nonce and a higher fee: either the same transaction (to speed it up) or a zero-value send to yourself (to cancel it). Wallets typically expose both as speed-up and cancel buttons.
Can other people see my transaction before it confirms?
In the public mempool, yes — pending transactions are fully visible, and bots actively parse them, which is what makes front-running and sandwich attacks possible. Keeping slippage tolerance tight limits what such bots can extract from a swap, and on EVM a growing share of traffic uses private submission channels that skip the public pool entirely, trading that transparency for protection.