mempool.space in depth : explorer, fees, API, self-host

Before mempool.space×mempool.spaceReference open-source Bitcoin explorer in 2026. Visualisation of blocks, fees and the mempool. Launched by Wiz and the mempool.space team.See in the lexicon →, reading the Bitcoin mempool×MempoolWaiting area where Bitcoin transactions sit before being included in a block. The fuller the mempool, the higher the fees required.See in the lexicon → and estimating fees required either the command line on your own node×NodeComputer that runs the Bitcoin software and takes part in the network by validating blocks and transactions. A « full node » keeps a complete copy of the blockchain.See in the lexicon → (not accessible) or explorers run by chain analysis companies that resold the queries. The 2019 launch of mempool.space by Wiz and his team changed the landscape : a clean visualisation of the mempool, free, without tracking, open under MIT licence, and fully self-hostable for those wanting maximum privacy.

In 2026, mempool.space has become the reference Bitcoin explorer for the technical community. The team lives on donations and partnerships with a few exchanges and wallets that fund features without imposing editorial censorship. The code is on GitHub×GitHubWeb platform that hosts most of the world's open-source projects, including Bitcoin Core, electrs, BDK and LDK. Lets you read the code, browse change history and submit contributions.See in the lexicon → (mempool/mempool), audited by the community, deployed on hundreds of personal and institutional nodes.

This article dissects mempool.space's interface, explains its mempool map, its next-blocks histogram, how to use it to estimate your own fees, its free public API×API (Application Programming Interface)Interface that lets one program query another program or service. mempool.space exposes a public API for querying the chain.See in the lexicon →, its self-hosted version, its mempool alerts, and its serious alternatives. For those wanting to leave the Google Search or Blockchain×BlockchainA public, shared ledger that records every Bitcoin transaction in blocks linked together cryptographically. Each participant in the network keeps a copy.See in the lexicon →.com reflex and use a real Bitcoin tool.

The interface : mempool map and recent blocks

The mempool.space×mempool.spaceReference open-source Bitcoin explorer in 2026. Visualisation of blocks, fees and the mempool. Launched by Wiz and the mempool.space team.See in the lexicon → homepage displays three main elements. On the left, the mempool×MempoolWaiting area where Bitcoin transactions sit before being included in a block. The fuller the mempool, the higher the fees required.See in the lexicon → map : a treemap where each rectangle represents a pending transaction, sized by its weight and coloured by its fee rate (sat/vB×sat/vB (satoshi per vbyte)Standard unit for expressing the Bitcoin fee rate. A typical transaction is 100 to 250 vB. At 5 sat/vB it costs 500 to 1,250 sats.See in the lexicon →). The yellowest transactions pay most, the reddest pay least. In the centre, the next expected blocks : 1 to 4 rectangles representing the blocks miners are currently building with mempool transactions, sorted by decreasing fee.

On the right, recently mined blocks : with mining×MiningProcess of validating blocks through proof of work. Consumes electricity by design : that is what secures the network.See in the lexicon → time, number of transactions, median fee, and the option to click for details. Everything updates in real time without page reload, making it a very readable dashboard to feel the network state at a glance.

At the top, the navigation bar lets you search by transaction (TXID), address (any Bitcoin format), block (height or hash×HashFunction that turns data of any size into a fixed-size fingerprint. The same input always yields the same output, but you cannot go back from output to input.See in the lexicon →), or xpub×xpub (extended public key)Extended public key. Lets a read-only wallet see addresses and balances without being able to sign. Used for tracking and observation.See in the lexicon → (extended public key×Public keyNumber derived mathematically from the private key, used to build a Bitcoin address. Can be shared freely.See in the lexicon →, useful to track a whole wallet×WalletSoftware or device that manages your Bitcoin keys and lets you sign transactions. A wallet does not really « hold » your bitcoins, it holds the keys that prove you own them.See in the lexicon →). The Languages dropdown switches between about twenty languages including FR/EN/DE/IT. The Mode menu offers Light/Dark/Custom and a mempool.live mode for real-time large-screen streaming (useful at a conference or in a store).

Estimating a correct fee without overpaying

The most practical use case of mempool.space×mempool.spaceReference open-source Bitcoin explorer in 2026. Visualisation of blocks, fees and the mempool. Launched by Wiz and the mempool.space team.See in the lexicon → is fee estimation for a transaction you are about to send. The homepage shows three clear recommendations : "No Priority" (the minimum fee to enter the next blocks without urgency), "Medium Priority" (median fee of the next blocks, ~30-60 minutes typical wait), "High Priority" (the fee needed to be included in the next block, ~10 minutes).

To go further, the Mempool×MempoolWaiting area where Bitcoin transactions sit before being included in a block. The fuller the mempool, the higher the fees required.See in the lexicon → tab shows a distribution graph by fee rate (sat/vB×sat/vB (satoshi per vbyte)Standard unit for expressing the Bitcoin fee rate. A typical transaction is 100 to 250 vB. At 5 sat/vB it costs 500 to 1,250 sats.See in the lexicon →) across all pending transactions. You visually read : "if I pay 15 sat/vB, my transaction will be included in about 2-3 blocks (~20-30 minutes), if I pay 5 sat/vB it is more random (1 to 4 hours), if I pay 1 sat/vB I can wait hours or days in heavy congestion".

2026 rule of thumb : during an activity lull (weekend, night), 1-3 sat/vB is enough for most non-urgent transactions. During a peak (post-halving×HalvingScheduled event every 210,000 blocks (roughly every 4 years) that cuts the miner reward in half. This mechanism makes Bitcoin issuance decline towards the total cap of 21 million.See in the lexicon →, ETF launch, ordinals×Ordinals (inscriptions)Protocol (2023) that numbers each satoshi and allows inscribing data (images, text) directly on-chain via Tapscript. At the origin of the debate on block space usage.See in the lexicon → frenzy), can climb to 100-200 sat/vB. Watching for 5 minutes the next-blocks area and the median fee gives a solid reference. And always prefer Lightning for daily payments, which entirely avoids this market.

Tracking a transaction, address or xpub

When you send a transaction, the wallet×WalletSoftware or device that manages your Bitcoin keys and lets you sign transactions. A wallet does not really « hold » your bitcoins, it holds the keys that prove you own them.See in the lexicon → shows the TXID (transaction hash×HashFunction that turns data of any size into a fixed-size fingerprint. The same input always yields the same output, but you cannot go back from output to input.See in the lexicon →). Pasting this TXID in mempool.space×mempool.spaceReference open-source Bitcoin explorer in 2026. Visualisation of blocks, fees and the mempool. Launched by Wiz and the mempool.space team.See in the lexicon →'s search bar opens the detail page : inputs, outputs, fee paid, size, status (in mempool×MempoolWaiting area where Bitcoin transactions sit before being included in a block. The fuller the mempool, the higher the fees required.See in the lexicon → / confirmed), number of confirmations, link to the confirming block. The page also offers RBF×RBF (Replace-By-Fee)Mechanism that lets you replace an unconfirmed transaction with a new one carrying higher fees, in order to speed it up.See in the lexicon → (Replace-By-Fee), CPFP×CPFP (Child Pays For Parent)Alternative to RBF where a high-fee child transaction pulls its stuck parent out of the mempool.See in the lexicon → (Child-Pays-For-Parent) and paid acceleration via Mempool Accelerator if the transaction is stuck.

Searching a Bitcoin address×Bitcoin addressString of characters that identifies a destination for receiving bitcoins. Four main formats, starting with 1..., 3..., bc1q... or bc1p... (Taproot, the recommended format in 2026).See in the lexicon → shows its full history : received and sent transactions, balance, first and last activity. Useful to verify×Don't trust, verifyBitcoiner mantra. Trust no one (bank, government, exchange, influencer), verify on your own through your own node.See in the lexicon → an expected payment arrived, or to audit a public company address. Caution : this search leaks the address to the mempool.space server (privacy issue if you search an address belonging to you from an identifiable IP).

Searching an xpub×xpub (extended public key)Extended public key. Lets a read-only wallet see addresses and balances without being able to sign. Used for tracking and observation.See in the lexicon → (extended public key×Public keyNumber derived mathematically from the private key, used to build a Bitcoin address. Can be shared freely.See in the lexicon →) is more powerful : mempool.space automatically derives the first dozens of addresses of the corresponding wallet and shows the aggregated view. Very useful to track a personal or business wallet. But it is the most privacy-leaking query possible : you give mempool.space the ability to monitor your entire wallet. For that reason, xpub usage on the public mempool.space is discouraged : prefer a self-hosted mempool.space connected to your own node×NodeComputer that runs the Bitcoin software and takes part in the network by validating blocks and transactions. A « full node » keeps a complete copy of the blockchain.See in the lexicon → (see section 60).

The public API for scripts and alerts

mempool.space×mempool.spaceReference open-source Bitcoin explorer in 2026. Visualisation of blocks, fees and the mempool. Launched by Wiz and the mempool.space team.See in the lexicon → exposes a public REST API×API (Application Programming Interface)Interface that lets one program query another program or service. mempool.space exposes a public API for querying the chain.See in the lexicon → documented on mempool.space/api. Free and without API key required for low-frequency queries, it lets you automate roughly everything the graphical interface does. Some useful endpoints : /api/v1/fees/recommended (recommended fees in JSON), /api/v1/mempool×MempoolWaiting area where Bitcoin transactions sit before being included in a block. The fuller the mempool, the higher the fees required.See in the lexicon → (full mempool state), /api/tx/{txid} (transaction detail), /api/block/{hash×HashFunction that turns data of any size into a fixed-size fingerprint. The same input always yields the same output, but you cannot go back from output to input.See in the lexicon →} (block detail), /api/address/{addr} (transactions and balance of an address).

Typical use cases. A script watching fees and sending a notification when they drop below a threshold (useful to defer a non-urgent transaction). A homemade dashboard aggregating several xpubs without depending on the graphical interface. A Telegram bot posting new blocks or important transactions. A backup script timestamping chainstate hashes for audit.

Practical limits. The undocumented rate limit is generous but exists : do not spam the public API with thousands of requests per second, either by looping reasonably, or by self-hosting your instance (see next section). For industrial use cases (BTCPay integration, trading platform, 24/7 enterprise monitoring), self-hosting is recommended anyway to avoid depending on an external service.

Self-hosting mempool.space on your own node

For those wanting a mempool.space×mempool.spaceReference open-source Bitcoin explorer in 2026. Visualisation of blocks, fees and the mempool. Launched by Wiz and the mempool.space team.See in the lexicon → with no leakage to the outside, self-hosting is the way. The mempool×MempoolWaiting area where Bitcoin transactions sit before being included in a block. The fuller the mempool, the higher the fees required.See in the lexicon →/mempool project on GitHub×GitHubWeb platform that hosts most of the world's open-source projects, including Bitcoin Core, electrs, BDK and LDK. Lets you read the code, browse change history and submit contributions.See in the lexicon → offers several install paths. The simplest : a docker×DockerTechnology that packages an application and its dependencies into an isolated container that can be started with one command on any system.See in the lexicon →-compose starting the necessary services (Angular frontend, Node×NodeComputer that runs the Bitcoin software and takes part in the network by validating blocks and transactions. A « full node » keeps a complete copy of the blockchain.See in the lexicon →.js backend, MariaDB×MariaDBDatabase used by CapBitcoin, an open-source fork of MySQL. Functionally very close.See in the lexicon → database, electrs to index the chain, connection to the local Bitcoin Core×Bitcoin CoreReference implementation of the Bitcoin software, written in C++ and maintained by an open-source community. This is the software that most nodes run.See in the lexicon → node). Launching the whole thing takes about fifteen minutes on a mini-PC×Mini-PC (NUC)Small fanless computer such as Intel NUC, Beelink or Minisforum. More powerful than a Raspberry Pi, ideal for a serious node running Lightning and BTCPay.See in the lexicon → already equipped with Bitcoin Core.

Packaged Bitcoin distributions (Umbrel×UmbrelEquivalent distribution for mini-PCs or Raspberry Pi, with a polished web interface and an app store (BTCPay, mempool.space, Sparrow Server, and so on).See in the lexicon →, Start9×Start9 (StartOS)Umbrel alternative focused on sovereignty and privacy. More technically demanding, more rigorous on privacy.See in the lexicon →, RaspiBlitz×RaspiBlitzReady-made software distribution that turns a Raspberry Pi into a Bitcoin and Lightning node. A pioneer of the genre, with an active German-speaking community.See in the lexicon →, MyNode×MyNodeAnother full-stack node distribution, with a commercial model and a paid Premium tier.See in the lexicon →) integrate mempool.space as an app installable in two clicks from their store. It is the simplest option for those already having one of these setups. The mempool.space app then runs on the node, accessible via a local URL (http://umbrel.local/mempool or equivalent) or via Tor for secure remote access.

The self-hosting advantage goes beyond privacy. No API×API (Application Programming Interface)Interface that lets one program query another program or service. mempool.space exposes a public API for querying the chain.See in the lexicon → rate limit (the machine is yours). No dependency on a third-party service in case of outage or censorship. Ability to add your own modifications to the source code. The downside : a full Bitcoin Core node is required (~620 GB storage), plus about 80 GB for electrs, plus maintenance. For those already running a node, it is a marginal cost ; for those who do not, it is the occasion to set one up (see Advanced articles).

Mempool alerts and serious alternatives

Mempool×MempoolWaiting area where Bitcoin transactions sit before being included in a block. The fuller the mempool, the higher the fees required.See in the lexicon → Alerts is the alert service offered by the mempool.space×mempool.spaceReference open-source Bitcoin explorer in 2026. Visualisation of blocks, fees and the mempool. Launched by Wiz and the mempool.space team.See in the lexicon → team since 2024. Free up to a reasonable quota, paid for intensive uses. Use cases : receive an email or Telegram notification when an interesting transaction confirms, when an xpub×xpub (extended public key)Extended public key. Lets a read-only wallet see addresses and balances without being able to sign. Used for tracking and observation.See in the lexicon → receives a payment, when fees drop below a threshold, or when fees rise above a threshold. Useful to automate operational decisions without watching mempool.space all the time.

Mempool Accelerator is a complementary service that lets you pay for a transaction stuck in the mempool to be included faster, via a direct agreement with partner mining×MiningProcess of validating blocks through proof of work. Consumes electricity by design : that is what secures the network.See in the lexicon → pools. Useful in the rare cases where a transaction is stuck due to too low a fee and you cannot do RBF×RBF (Replace-By-Fee)Mechanism that lets you replace an unconfirmed transaction with a new one carrying higher fees, in order to speed it up.See in the lexicon → (for example if the transaction is already signed by an unavailable cosigner).

Serious mempool.space alternatives. Blockstream.info (by Blockstream, open source×Open sourceSoftware whose source code is public and modifiable by anyone. A fundamental auditability guarantee in Bitcoin.See in the lexicon →, similar in philosophy but fewer visual features). Mempool.observer (community variant, some analysts publish advanced statistics there). For pure transaction lookup, the REST API×API (Application Programming Interface)Interface that lets one program query another program or service. mempool.space exposes a public API for querying the chain.See in the lexicon → of your own Bitcoin Core×Bitcoin CoreReference implementation of the Bitcoin software, written in C++ and maintained by an open-source community. This is the software that most nodes run.See in the lexicon → does the job internally. Institutional explorers (BTC.com, Blockchair, OKLink) remain to avoid for those caring about privacy : they trace queries and resell them.