The European Central Bank is moving the digital euro from planning into testing, with dozens of payment companies joining the next stage of the project.

The ECB selected 36 payment service providers (PSPs) to participate in a digital euro pilot, according to an official announcement published Tuesday.

The list of selected PSPs includes fintechs Stripe and Revolut alongside traditional banks including Deutsche Bank, UniCredit and BPCE. Revolut has recently adjusted some cryptocurrency services for EU users by phasing out support for Tether USDt.

The pilot comes as governments take different approaches to digital currencies. While Europe is expanding testing of its proposed central bank digital currency (CBDC), the US has moved to block the Federal Reserve from issuing a CBDC.

Italy tops list of digital euro pilot providers

The ECB began selecting providers from across the euro area for its digital euro pilot earlier this year, with the 12-month trial set to begin in the second half of 2027.

The central bank said it received more than 50 applications from payment companies after opening a call for interest in March 2026. The selected participants include traditional banks, payment processors and non-bank service providers.

Source: ECB

Italy has the largest number of selected participants, with seven companies joining the pilot, including UniCredit, Poste Italiane, Nexi Payments, Banca Sella, Banca Monte dei Paschi di Siena, Isybank and Numia.

Germany follows with five selected providers, while Portugal and Greece each have three. The ECB said the mix of countries is designed to create a broad testing environment, with selected providers able to offer pilot services outside their home markets.

Strong interest in digital euro pilot

ECB Executive Board member Piero Cipollone, who chairs the high-level task force on a digital euro, said the level of participation shows private-sector interest in helping develop it, adding that the Central Bank expects deeper cooperation with payment providers during the pilot.

“We look forward to deeper engagement as we work with and learn alongside European payment service providers in developing a secure, efficient and inclusive digital euro,” Cipollone said.

Related: South Korea to test tokenized government bonds with CBDC in 2027

The pilot will involve the ECB and the central banks of 19 bloc-members, including Belgium, Germany, France, Italy, Spain and the Netherlands, alongside payment companies and merchants testing the system before any potential token issuance.

Selected providers will have different responsibilities during the trial, with some focused on supporting user access to beta digital euro services and others helping merchants accept payments. Several companies will take on both roles, the ECB said.

Magazine: The 5 types of real world assets being tokenized fastest onchain

Reed Smith has launched an automated MiCA compliance platform as crypto firms across the European Union have entered full regulatory supervision following the end of the bloc’s transition period.

According to global law firm Reed Smith, the new platform, called Aquarius, automates key compliance tasks under the European Union’s Markets in Crypto-Assets (MiCA) regulation, including crypto-asset classification, regulatory white paper generation, due diligence and environmental, social and governance (ESG) disclosures.

Designed for companies entering the European market or expanding existing crypto services, the platform combines automated compliance workflows with legal support to simplify MiCA requirements. Reed Smith said future versions will also support crypto compliance regimes in the United Kingdom, the United Arab Emirates, Hong Kong, and Singapore.

The launch comes shortly after the European Union’s MiCA transition period ended on July 1, when crypto companies could no longer rely on temporary national exemptions in member states that adopted the full grandfathering period. The framework now requires crypto-asset service providers to meet common licensing, consumer protection, and operational standards across all 27 EU member states.

Reed Smith has continued expanding its digital asset practice through its “On Chain” initiative. The firm acted as legal counsel to the placement agents in Trump Media’s $2.5 billion Bitcoin treasury financing and also advised Nakamoto Holdings on its merger with KindlyMD to establish a Bitcoin treasury company.

Focus moves from licensing to supervision

Recent regulatory activity indicates that European authorities are now concentrating on how licensed firms operate after receiving approval.

Last week, the European Securities and Markets Authority (ESMA) began a Common Supervisory Action covering selected MiCA-authorized crypto-asset service providers. According to ESMA, the review examines custody operations, including private key management, transaction controls, incident response procedures and reliance on third-party technology providers.

Sebastien Dessimoz, co-founder and managing partner of digital asset infrastructure provider Taurus, previously said obtaining a MiCA licence is only the starting point for custodians because regulators now expect firms to demonstrate that their operational controls can withstand real-world risks. He added that supervision increasingly focuses on cybersecurity, governance and protection of client assets rather than licensing alone.

Institutional expectations have also increased. Jody Mettler, chief operating officer of BitGo and president of BitGo Trust, previously said clients are paying closer attention to how custodians segregate customer assets, control access, respond to security incidents and maintain business continuity during periods of market stress.

Meanwhile, European policymakers continue discussing possible changes to MiCA after its rollout. According to a Euronews report, officials are considering future revisions to stablecoin rules, including the treatment of non-euro-denominated stablecoins, following the passage of the United States’ GENIUS Act.

The European Parliament has also asked the European Commission to examine whether decentralized finance, staking, crypto lending and borrowing, non-fungible tokens and tokenized financial assets should receive more specific treatment under the EU’s crypto framework. Parliament’s position does not change the law but provides political support for further reviews, while any expansion of MiCA would still require separate legislative proposals.

US Treasury Secretary Scott Bessent confirmed the US government ordered the freezing of more than $130 million in cryptocurrency held in wallets linked to Iran on Tuesday, as hostilities ramped up in the Middle East. 

Earlier on Tuesday, blockchain investigator Specter pointed to onchain data showing Tether froze four Tron wallets holding $131 million worth of USDt (USDT). Bessent confirmed on X that the wallets were tied to the Central Bank of Iran. 

“US Treasury is committed to disrupting and degrading Iran’s illicit financial activities, including its abuse of digital assets,” Bessent said Tuesday. “We will continue to aggressively follow the money and deny the Iranian regime access to the proceeds of its illicit revenue schemes.”

The asset freeze comes amid a collapse in the ceasefire between the US and Iran. The US said it has renewed its blockade of Iranian ports, while the US military’s Central Command announced a new wave of strikes on Iran. Meanwhile, Iran’s military claimed on Tuesday that it carried out drone strikes against US military facilities at Jordan’s Al Azraq Air Base. 

Source: Scott Bessent

The move follows a similar freeze in April, when stablecoin issuer Tether confirmed it had frozen more than $344 million in USDT at the request of US authorities. 

In May, Bessent said the US has seized around $1 billion in Iranian crypto assets as part of the US financial pressure campaign against Iran known as Operation Economic Fury, which launched in March 2025. 

Related: Iran-linked entities moved $3.8B through CoinEx, TRM says 

“Through Economic Fury, the Treasury Department is disrupting the foreign procurement networks that support the Iranian military’s efforts to acquire weapons,” Bessent said in a statement in June.  

“Treasury has frozen the Iranian regime’s assets, severely disrupted its economy, and dismantled the Iranian war machine. Treasury will not tolerate any support of the Iranian military.” 

Magazine: Thai scammer’s $122M wallet, Japan embraces crypto credit: Asia Express

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Confirmo has launched a stablecoin subscription payment service that supports automated recurring billing across more than 700 self-custody wallets and exchange accounts.

According to a July 14 press release shared with crypto.news, Subscribe allows enterprise businesses such as SaaS providers, trading platforms, and subscription services to add recurring stablecoin payments to their existing payment systems without developing the infrastructure internally.

The product has arrived as the global subscription economy is projected to reach $1.2 trillion by 2030, while Confirmo said more than 700 million people, or about 8.5% of the global population, now hold digital assets.

Built on Solana and Polygon, Subscribe initially supports Circle-issued USDC and Paxos-issued USDG. Paxos also serves as Confirmo’s US infrastructure partner, with the companies working together on stablecoin infrastructure and market access.

Subscribe supports wallets and exchange accounts

Unlike services limited to self-custody wallets, Subscribe accepts payments from both wallets and exchange accounts. WalletConnect integration gives customers access through more than 700 supported wallets, according to Confirmo.

Once a customer approves a subscription, the system automatically pulls stablecoins from the selected wallet or account on each billing date. Every payment is recorded from the outset, allowing merchants to monitor completed and scheduled transactions.

Existing Confirmo clients can view subscription activity through the same dashboard used for their other stablecoin payment products. The combined view removes the need to manage recurring transactions through a separate system.

Subscription plans are priced in US dollars to limit exposure to digital asset price changes. Confirmo said stablecoin settlement can also lower cross-border costs and reduce unexpected charges for customers.

Card declines and failed billing attempts can cause subscribers to lose access to a service without choosing to cancel. The company said wallet-based pull payments remove some of those failure points by collecting funds automatically after the customer grants approval.

Anna Kratky Strebl, Group CEO at Confirmo, said the service was developed around the payment needs of the company’s business customers.

“Built in collaboration with our long-term customers, it gives merchants a more transparent, cost-effective way to manage subscription and recurring revenue models, while making it easier for consumers worldwide to pay with the wallets and accounts they already use,” Strebl said.

She added that Confirmo would continue adapting its services as stablecoins become part of mainstream financial infrastructure and businesses seek new digital payment models.

FTMO helped design the payment system

Confirmo developed Subscribe with proprietary trading firm FTMO, which served as the product’s design partner. The collaboration allowed the infrastructure provider to test the system against the operational requirements of an existing merchant before launch.

Milan Flosman, Head of Finance Operations at FTMO, said the service would allow the company to introduce automated stablecoin billing without building its own payment system.

“Subscribe will give us something that didn’t exist before, a way to run automated, recurring stablecoin billing without building it ourselves,” Flosman said.

He added that Confirmo understood FTMO’s setup through the companies’ existing relationship and built the service to integrate with its operations.

“We’re not just looking to accept a new payment method; we’re preparing to launch a new payment model entirely,” Flosman said.

Stablecoin payments continue expanding beyond trading

The launch comes as businesses continue adopting stablecoins for commercial payments instead of limiting their use to crypto trading.

As previously reported by crypto.news, stablecoin cross-border payments were priced below interbank foreign exchange rates throughout the second quarter of 2026, Borderless.xyz highlighted in its Q2 2026 benchmark.

The firm tracked 260 payment corridors across 108 countries using nearly three million exchange rate observations and found stablecoin transfers maintained predictable pricing while provider selection became the largest factor affecting payment costs.

Borderless.xyz also reported that real-world stablecoin payment volume doubled to about $400 billion in 2025 as business-to-business payments, payroll and cross-border settlement gained traction. 

The report said payment providers have continued expanding stablecoin services across new markets, with companies including dLocal and SBI Remit increasing support for international payment corridors.

XRP traded near $1.07 on July 14 after losing about 1% over 24 hours. 

The token moved between $1.06 and $1.08, with daily volume near $955 million and market capitalization around $66.7 billion. Ripple’s native token remained the sixth-largest cryptocurrency.

The price has fallen nearly 6% over seven days and about 7% over one month. It also sits more than 70% below its July 2025 record of $3.65. The latest data shows weak price action near a support area defended several times since late June, while buyers still lack a clear breakout signal.

XRP price remains below key resistance

The XRP/USDT daily chart shows a broader decline from the $1.40 to $1.50 region. Price has stabilized between $1.05 and $1.10, but buyers have not reclaimed the recent recovery zone near $1.15 to $1.20. Analyst Cryptorphic said lower levels remain possible “as long as $1.08 remains resistance.”

$XRP is slowly moving toward the short-term downside target after losing the rising trendline support.
For now, lower levels seem likely as long as $1.08 remains resistance.

This short setup is looking interesting here, and the current structure favors sellers while price stays… pic.twitter.com/Fy9N9NVATm

— Cryptorphic (@Cryptorphic1) July 14, 2026

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The nearest downside level sits around $1.05. A daily close below that area could expose the psychological $1.00 mark. A recovery above $1.08 would ease immediate pressure, while a move through $1.10 could open another test of $1.14 and $1.18.

The relative strength index stood near 40.30, below its signal average of 45.68. The MACD histogram turned slightly positive, but the MACD and signal lines stayed below zero. That setup points to minor stabilization rather than a confirmed trend change, because both momentum lines remain in negative territory.

Binance order flow continues to favor sellers

A CryptoQuant analysis by Arab Chain found that XRP’s Binance Cumulative Volume Delta remained negative at about 6.93 million. CVD measures the difference between market buy and sell orders. A negative reading means sellers executed more volume than buyers.

The 30-day Price-CVD Confirmation Score held near 0.84. The analyst said the reading confirms that price and order flow continue to move together, but does not show enough buying demand for a reversal. A sustained move in CVD above zero, with a rising score, would offer clearer evidence that buyers have returned.

The data supports the short-term chart structure. The token has stayed close to $1.07 while spot sellers limit rebounds. Binance remains one of the largest XRP markets, making its order flow useful for judging whether price moves have support from spot demand.

Bullish social sentiment creates a mixed signal

Santiment said XRP recorded 3.02 bullish comments for every bearish comment on Monday. Ether followed at 2.31, while Bitcoin posted a more balanced ratio of 1.40. XRP therefore carried the strongest level of optimism among the three assets.

Santiment warned that crowded optimism can work against prices when markets already trade lower. “Crypto typically moves opposite to what the crowd is loudly expecting,” the firm wrote. It said strong bullish discussion around XRP and Ether could slow a rebound or create short-term downside risk.

✍️ TL;DR: 5-week high FOMO appears for XRP and Ethereum
📊 Metrics Used: Positive vs. Negative Commentary Ratio
🔗 Live Chart: https://t.co/icmgnCJiFT

📊 Sentiment is no longer fearful across the big three, but it’s also not evenly balanced. On Monday, $XRP is showing the most… pic.twitter.com/3SgH7R1MUG

— Santiment Intelligence (@SantimentData) July 13, 2026

The reading follows an earlier rise in XRP network growth and social interest near the $1 support region. New activity can attract buyers, but sentiment alone does not confirm demand. The split between positive commentary and negative Binance order flow keeps attention on both price and liquidity.

$50 XRP scenario depends on a $100 trillion crypto market

Crypto commentator Moon Lambo calculated that XRP could reach $50.10 if the total cryptocurrency market grew to $100 trillion and XRP retained a 3.13% share. That outcome would assign about $3.13 trillion in value to XRP, based on its circulating supply.

Moon Lambo stated, “I’m not making a prediction.” The calculation only shows price under fixed assumptions. At a 1% share of a $100 trillion market, XRP would trade near $16.01. A 5% share would place it around $80.08, while 10% would imply about $160.15.

Those figures do not describe XRP’s current market setup. The global crypto market would need to expand many times, while XRP would need to retain or increase its share. Supply changes, adoption, regulation and market structure would also affect future valuation.

XRP entered July between support around $1.00 to $1.06 and resistance near $1.18 to $1.20. Spot XRP exchange-traded funds also recorded $7.29 million in net outflows on July 8, their largest daily withdrawal since March.

A former Los Angeles County Sheriff’s Department deputy has been sentenced to 18 months in federal prison after admitting he lied to federal investigators about threats made by a cryptocurrency businessman during a 2021 extortion incident.

The U.S. Attorney’s Office for the Central District of California said U.S. District Judge Percy Anderson also imposed a $10,000 fine on Scott Allen Simpkins, who pleaded guilty on March 17 to one count of obstruction of justice. Simpkins resigned from the Los Angeles County Sheriff’s Department’s Special Enforcement Bureau after entering his felony plea, according to the office.

Federal prosecutors said Simpkins falsely denied witnessing cryptocurrency businessman Adam Iza threaten a victim with live ammunition during an incident at Iza’s Bel Air home in 2021.

Court records cited by the U.S. Attorney’s Office said Simpkins was working private security at the residence with fellow former LASD deputy Christopher Michael Cadman. Both men were employed by Saavedra & Associates, a private security company owned by then-LASD Deputy Eric Chase Saavedra.

According to prosecutors, Iza placed four or five live 9mm rounds on his desk, spun one of the bullets while threatening the victim, and demanded a $25,000 transfer before Simpkins and Cadman escorted the victim off the property.

The U.S. Attorney’s Office said the two deputies received $1,400 each for their work that day. After helping Saavedra & Associates secure a longer-term security contract with Iza, the company paid each of them about 10% of its profits from the contract’s first month, prosecutors added.

Iza still awaits sentencing

Separate federal cases against Iza have continued to move forward.

The U.S. Attorney’s Office said Iza has remained in federal custody since September 2024 after pleading guilty in California in January 2025 to conspiracy against rights, wire fraud, and tax evasion. He has not yet been sentenced in that case.

In a separate prosecution, the U.S. Department of Justice announced in June that Iza also pleaded guilty in federal court in Connecticut to conspiracy to interfere with commerce by robbery. The charge carries a maximum prison sentence of 20 years.

According to the Justice Department, the Connecticut case involved a 2024 kidnapping plot targeting the parents of Veer Chetal, a man accused of participating in the theft of about 4,100 bitcoin. Prosecutors said Iza and his brother, Saif Faiq, organised the scheme in an attempt to extort cryptocurrency.

As pre DOJ records, Faiq pleaded guilty on June 9, when he admitted recruiting six men from Florida, arranging their travel to Connecticut, and coordinating surveillance before the attack in Danbury. Prosecutors said the group allegedly forced Sushil and Radhika Chetal from their vehicle after staging a collision, assaulted them, and briefly held them captive. The six alleged attackers later pleaded guilty to kidnapping and carjacking offences, according to the department.

Federal records cited by the DOJ show Veer Chetal separately pleaded guilty in November 2025 to charges connected to the theft of approximately 4,100 bitcoin and is awaiting sentencing.

You press send on a crypto transaction and nothing happens. The wallet says pending. The block explorer shows your transaction floating in limbo, unconfirmed, with no clear indication of when, or whether, it will land.

Most people meet the mempool for the first time in exactly this moment of mild panic, and most of the advice they find assumes they already know what a mempool is. This guide starts from zero.

The mempool, short for memory pool, is the waiting room where every blockchain transaction sits between the moment you broadcast it and the moment a miner or validator writes it into a block. It is one of the least glamorous components of a public blockchain and one of the most consequential. The mempool decides how much you pay in fees, how long you wait, and, on some networks, whether a trading bot gets to see your order before it executes and profit at your expense. Understanding it turns confirmation delays from a mystery into a readable market signal.

This guide explains what the mempool actually is, why blockchains need a waiting room at all, how transactions move through it step by step, how fee markets decide who gets confirmed first, why there is no single mempool but thousands of slightly different ones, what happens when the queue overflows, how the mempool became the hunting ground for extractive trading bots, why Solana took the radical step of removing the public mempool entirely, and what practical steps you can take when your own transaction gets stuck.

What a mempool actually is

A mempool is a database of unconfirmed transactions that every full node on a blockchain network maintains in its working memory. When you sign a transaction in your wallet and hit send, the transaction does not travel to some central server for processing, because no such server exists. Instead, your wallet hands the signed transaction to a node, and that node begins spreading it to its peers, who spread it to their peers, until most of the network has a copy. Each node that receives the transaction runs a series of checks and, if the transaction passes, places it in its local mempool to wait.

The word itself is a contraction of memory and pool, and the memory part matters. Nodes keep the mempool in RAM instead of writing it to disk, because speed is the point. When a miner assembles a candidate block, it needs to sort thousands of pending transactions by fee and select the most profitable set in a fraction of a second. When a new block arrives from elsewhere on the network, a node can validate it faster if most of the block’s transactions are already sitting in its own mempool, checked and ready.

The mempool is a staging area, a buffer between the chaotic, continuous stream of user activity and the rigid, periodic heartbeat of block production.

Why blockchains need a waiting room

A traditional payment processor confirms transactions the instant they arrive because a single company controls the ledger and can simply write the entry. A public blockchain has no such authority. Thousands of independent nodes must agree on a single history, and they reach that agreement in discrete steps, one block at a time. Between blocks, the network needs a shared, informal picture of what users want to happen next, and the mempool provides it.

The waiting period also does critical security work. Before a node admits a transaction to its mempool, it verifies that the digital signature is valid, that the sender actually controls the funds being spent, that the transaction is correctly formatted, and that the same coins are not being spent twice. This last check matters more than it sounds. It is entirely possible for two conflicting transactions, both spending the same coins, to enter the network at the same time from different points. Some nodes see one first, some see the other. Each node rejects whichever conflicting transaction arrives second, and the conflict is finally settled when a miner includes one of the two in a block. The mempool is where these races are held and resolved.

The mempool also functions as the network’s early warning system. A rapidly filling mempool signals a surge of demand, a panic, an airdrop claim window, or a fee spike before any of it shows up in confirmed blocks. Traders, miners, and wallet fee estimators all read the mempool the way meteorologists read pressure systems.

The life of a transaction, step by step

Following a single transaction through the pipeline makes the mechanics concrete. First comes creation: your wallet constructs the transaction, specifying the amount, the recipient, and the fee you are willing to pay, and signs it with your private key. The signature proves ownership without revealing the key itself.

Second comes broadcast. The wallet sends the signed transaction to one or more nodes, which begin relaying it across the peer to peer network. Propagation to most of the network typically takes a few seconds, and nothing about this step requires trust in the first node, since every subsequent node re-validates the transaction independently before passing it along.

Third comes validation. Every node that receives the transaction independently checks it. Invalid transactions, bad signatures, insufficient funds, malformed data, are dropped on the spot and never reach a mempool.

Fourth comes the wait. The transaction now sits in thousands of mempools across the network, visible to anyone running a node or using a public mempool explorer. How long it waits depends almost entirely on the fee attached relative to everyone else’s fees.

Fifth comes selection. A miner on a proof of work chain, or a validator on a proof of stake chain, assembles a candidate block by picking pending transactions from its mempool, almost always sorting by fee density so the block earns the maximum reward.

Sixth comes confirmation. The block is mined or proposed, propagated, and accepted by the network. Every node removes the block’s transactions from its mempool, and your transaction is now part of the chain. Each additional block built on top adds another confirmation and makes reversal exponentially harder.

How the fee market decides who goes first

Block space is scarce and demand fluctuates, so blockchains ration space by auction. On Bitcoin, fees are measured in satoshis per virtual byte, a unit of transaction data size, so a transaction’s fee rate depends on both what you pay and how much space the transaction occupies. On Ethereum, the fee is gas, with a base fee that the protocol burns and a priority tip that goes to the validator. In both systems the logic is identical: block producers are profit maximizers, so they fill blocks with the highest paying transactions first.

This means your position in the queue is not fixed. A transaction that looked competitively priced at noon can be hopelessly underpriced by evening if demand surges. Wallets estimate fees by reading the current mempool, looking at what pending transactions are offering and how full recent blocks have been, then suggesting a rate likely to confirm within your chosen time window. Those estimates are educated guesses, not guarantees, and they go stale quickly during volatile markets. A fee that clears in the next block during a quiet Sunday can leave you waiting hours during a liquidation cascade, because everyone else’s willingness to pay moved while yours stood still. The auction never closes, and it reprices continuously.

When you underpay, most networks offer escape hatches. Bitcoin supports replace by fee, which lets you rebroadcast the same transaction with a higher fee that supersedes the original. A related trick, child pays for parent, attaches a high fee follow up transaction that spends the stuck one’s output, giving miners an incentive to confirm both together. Ethereum wallets let you resubmit a transaction with the same nonce and a higher gas price, which replaces the pending version. Knowing these tools exist converts a stuck transaction from an emergency into an inconvenience.

There is no single mempool

People say the mempool as if one canonical queue existed somewhere, but the reality is messier and more interesting. Every node maintains its own mempool, and no two are exactly identical. Transactions reach different nodes at different times, nodes apply slightly different acceptance policies, and each node manages its own memory limits. What we call the mempool is really the loose statistical overlap of thousands of private ones.

In practice the overlap is large, because most node operators run default settings. A typical Bitcoin node caps its mempool around 300 megabytes, keeps transactions for up to two weeks, and refuses anything paying less than a minimum relay fee of roughly one satoshi per virtual byte. When the pool exceeds its size cap, the node evicts the lowest fee transactions first and raises its minimum acceptance rate, which is why very cheap transactions can vanish entirely during congestion instead of merely waiting. Once evicted everywhere, a transaction is effectively cancelled, and the funds simply remain unspent in the sender’s wallet.

The distributed nature of the mempool has a subtle consequence: pending status is not a promise. A transaction shown as pending in an explorer exists only as a claim in some nodes’ memory. It can be evicted, replaced, or double spent until it lands in a block. Merchants who accept zero confirmation payments learn this lesson the hard way, and it is exactly the mechanism a 51% attack exploits at chain level, where an attacker rewrites recent blocks and dumps the reversed transactions back into the mempool as if they had never confirmed. The 2025 reorganization attacks on Monero pushed more than one hundred confirmed transactions back into the pending queue in exactly this way.

Policy, standardness, and why nodes reject valid transactions

Consensus rules define what a blockchain will accept in a block. Mempool policy defines what an individual node will hold and relay, and the two are not the same thing. A transaction can be perfectly valid under consensus rules and still be refused by most mempools because it violates what Bitcoin developers call standardness: informal policy rules that filter dust outputs, oversized scripts, absurdly low fees, and exotic transaction shapes that could burden the network. Policy is a node level immune system, a first line of defense that keeps the shared queue usable.

This distinction produces real world confusion. A transaction rejected by public mempools can still be mined if it reaches a miner directly, which is why services exist that accept nonstandard transactions out of band and submit them straight to mining pools. It also means the mempool you observe through an explorer reflects that node’s policy, not some universal truth. Two explorers can disagree about whether your transaction is pending simply because their nodes apply different filters.

Policy also evolves faster than consensus. Nodes have tightened and loosened relay rules around data inscriptions, dust limits, and replacement behavior repeatedly over the years, each change reshaping what the pending queue looks like without touching consensus at all. For users the practical takeaway is simple: if a wallet warns that a transaction is nonstandard, the problem is usually the transaction’s construction, not the funds behind it.

The mempool also has a quieter institutional audience. Exchanges watch pending deposits to credit accounts faster, compliance teams screen incoming transactions before confirmation, and payment processors estimate risk on zero confirmation transfers by checking how well a transaction is propagating and whether any conflicting spend is circulating. A transaction that most of the network’s mempools agree on is far less likely to be double spent than one propagating poorly, and firms price that difference.

Congestion, spam, and what a full mempool feels like

Mempool congestion is the network catching its breath. Demand exceeds block space, the queue grows, and the fee needed for timely confirmation climbs. Users experience it as expensive transactions and long waits. Bitcoin’s late 2017 mania, the DeFi summer of 2020, NFT minting waves, and the ordinals inscription craze of 2023 each produced mempool backlogs measured in days, with hundreds of thousands of transactions queued and fee rates multiplying overnight. During the worst stretches, low fee transactions waited more than a week, and node operators watched their mempools hit size limits and begin shedding the cheapest traffic.

Congestion can also be manufactured. Spam attacks flood the network with masses of low value transactions to clog the queue and degrade service for everyone else, a cheap form of denial of service. Networks defend themselves with the minimum relay fee, with eviction policies, and ultimately with economics, since sustained spam costs the attacker real money in fees. The 2017 spam attack on an Ethereum test network showed how effective flooding could be against a chain with weak fee pressure, and it pushed fee market design higher up the research agenda.

Congestion is also information. A swollen mempool alongside rising fees signals urgent demand, often around exchange runs, liquidation cascades, or major market moves. Sophisticated observers watch mempool depth the way bond traders watch yields, and several analytics firms sell exactly that feed.

The dark forest: MEV and the watchers in the pool

The mempool’s defining feature, total transparency, is also its greatest vulnerability. Every pending transaction is public before it executes, which means anyone can read your intentions and act on them first. On smart contract chains this gave rise to an entire extractive industry built around maximal extractable value, or MEV, the profit available to whoever controls transaction ordering.

The canonical attack is the sandwich. A bot spots your large pending swap on a decentralized exchange, buys the same token first to push the price up, lets your trade execute at the worse price, then immediately sells for a profit carved directly out of your execution. Front running, back running, and liquidation sniping follow the same principle: see the pending transaction, position around it, capture the difference. One researcher famously described the public mempool as a dark forest, a place where anything visible gets hunted. Researchers estimate that MEV extraction on Ethereum alone has run into the billions of dollars since 2020.

The defense industry that grew in response is now substantial. Private transaction relays, such as Flashbots Protect, let users submit transactions directly to block builders, skipping the public mempool entirely so bots never see the order. Batch auction exchanges settle many trades at a single clearing price, removing the ordering advantage. Wallets increasingly route large trades through protected channels by default. None of this eliminates MEV, but it changes who can be hunted. The economics are straightforward: the value of hiding an order grows with its size, so large traders now treat mempool privacy the way traditional funds treat dark pools, as basic operational hygiene. Retail users moving small amounts face far less risk, but a single large swap through the public queue on a thin trading pair can pay a triple digit toll to a sandwich bot in a matter of seconds.

Solana’s answer: delete the mempool

Solana made the most radical design choice of any major network: it has no public mempool at all. Instead of gossiping pending transactions across the whole network, Solana’s Gulf Stream protocol forwards transactions directly to the validator scheduled to produce the next block, called the leader. The leader schedule is known in advance, so wallets and nodes know exactly where to send traffic. Transactions go from user to leader with almost no public waiting period.

The design serves speed above all, and it removes the classic observation window that sandwich bots depend on, since pending transactions are never broadcast for public inspection. It did not eliminate MEV, which instead matured into a private auction economy where searchers pay tips through infrastructure such as Jito to have their transaction bundles placed favorably by leaders. The lesson generalizes: ordering has value on any blockchain, and removing the public queue changes where that value is captured, not whether it exists.

Other networks are converging on middle paths. Encrypted mempools hide transaction contents until ordering is locked. Proposer builder separation on Ethereum splits the job of choosing transactions from the job of proposing blocks, pushing MEV into a more transparent auction. The mempool of 2030 will likely look very different from the open bazaar of 2020. What will not change is the underlying constraint: some component of every blockchain has to hold transactions between creation and confirmation, and whoever can observe or influence that component holds power over everyone who cannot.

Reading the mempool yourself

You do not need to run a node to watch the queue. Public mempool explorers visualize pending transactions, fee distributions, and projected confirmation times in real time, and they are the fastest way to answer the two questions every stuck user asks: how busy is the network, and what fee actually clears right now.

When your own transaction is stuck, the diagnosis is almost always the same: your fee is below the going rate. Your options, in rough order of preference, are to wait for congestion to ease, to bump the fee using replace by fee or a nonce replacement, to use child pays for parent where supported, or, on Bitcoin, simply to wait for eviction if the payment no longer matters. What you should not do is panic. The funds are not lost. An unconfirmed transaction either confirms or effectively ceases to exist, and in the latter case the coins never left your wallet.

It also helps to understand what explorers actually display. The fee histogram shows how much pending volume sits at each fee level, which tells you where the clearing price is right now. The projected blocks view shows which transactions would fill the next several blocks if they were produced immediately, which tells you how deep the queue runs ahead of you. And the purge line, on Bitcoin explorers, shows the fee rate below which nodes are actively evicting transactions, the effective floor of the market. Ten minutes spent learning these three readouts pays for itself the first time fees spike.

One final habit worth adopting: check the mempool before you transact, not after. Thirty seconds of looking at current fee rates saves both overpaying during quiet periods and underpaying during storms. The queue is public. Very few people bother to read it, which is exactly why the ones who do have an edge. It is the same reason a network upgrade that splits the chain, covered in our guide to hard forks and soft forks, always produces a flurry of mempool drama, as wallets and nodes on both sides of the split sort out which pending transactions belong where.

Frequently asked questions

This article is for educational purposes only and does not constitute financial or investment advice. Network rules, fee mechanics, and default node policies change over time. Details are accurate as of July 14, 2026.