Mempool Explorer

Self-hosted Bitcoin mempool visualizer and block explorer. Build Mempool v3 from source, MariaDB backend, Caddy HTTPS on port 4080.

Mempool is the same open-source code that runs mempool.space, self-hosted on your own node. Transaction lookups, fee estimates, and UTXO queries stay on your LAN and never reach a third party.

This guide builds Mempool v3.3.1 from source. The backend stores indexed data in MariaDB and serves the API on port 8999. Caddy puts the Angular frontend behind HTTPS on port 4080.

Requirements

Electrum server running (Electrs on port 50001)
Node.js 22 installed (from the BTC RPC Explorer guide or standalone via nodesource.com)
Caddy installed (from the same guide or standalone via caddyserver.com)
~5 GB free on the SSD: build artefacts under /home/mempool/ take 4-5 GB; the MariaDB database starts small but grows to ~5 GB with full historical address indexing enabled
A Pi 5 with 8 GB of RAM. Older boards struggle, see below.

Pi 4 8 GB: expect instability

Mempool 3.x is memory-hungry. A community report on the v4 preview (raspibolt/raspibolt#1526) described v3.3.1 crashing on a Pi 4 8 GB after a few hours of normal load, with a pinned older release being the only way to keep it stable. If you're on a Pi 4, either accept the operational risk, pin to an older Mempool release in step "Clone Mempool" below (check git tag in the mempool repo and git checkout v3.0.0 or a similar earlier tag instead of the default branch), or skip this guide and use a public mempool.space mirror over Tor for occasional lookups.

Create the user

A dedicated system user limits the blast radius of any bug. Adding it to the bitcoin group lets Mempool authenticate to Bitcoin Core via the cookie file, the same approach BTC RPC Explorer uses.

Create the service user:

sudo adduser --disabled-password --gecos "" mempool

Add it to the bitcoin group:

sudo adduser mempool bitcoin

Install build dependencies

Mempool's backend includes a Rust-native block-template builder (GBT). Debian 13 Trixie ships Rust 1.85, which meets the 1.84 requirement:

sudo apt install rustc cargo

Set up MariaDB

sudo apt install mariadb-server

Create the database and a dedicated user. Replace YourPasswordM with your password [M] (new, used only for MariaDB here):

sudo mysql <<'SQL'
CREATE DATABASE mempool;
GRANT ALL PRIVILEGES ON mempool.* TO 'mempool'@'localhost' IDENTIFIED BY 'YourPasswordM';
SQL

Install Mempool

Clone and check out the release as the mempool user:

sudo -u mempool bash <<'EOF'
git clone https://github.com/mempool/mempool ~/mempool
cd ~/mempool
git checkout v3.3.1
EOF

Configure the backend

Write the config file. Replace YourPasswordM with your password [M]:

sudo -u mempool tee /home/mempool/mempool/backend/mempool-config.json > /dev/null <<'CONFIG'
{
  "MEMPOOL": {
    "NETWORK": "mainnet",
    "BACKEND": "electrum",
    "HTTP_PORT": 8999,
    "SPAWN_CLUSTER_PROCS": 0,
    "API_URL_PREFIX": "/api/v1/",
    "POLL_RATE_MS": 2000,
    "CACHE_DIR": "./cache",
    "CACHE_ENABLED": true,
    "CLEAR_PROTECTION_MINUTES": 20,
    "RECOMMENDED_FEE_PERCENTILE": 50,
    "BLOCK_WEIGHT_UNITS": 4000000,
    "INITIAL_BLOCKS_AMOUNT": 8,
    "MEMPOOL_BLOCKS_AMOUNT": 8,
    "INDEXING_BLOCKS_AMOUNT": 0,
    "AUDIT": false,
    "RUST_GBT": true,
    "CPFP_INDEXING": false,
    "ALLOW_UNREACHABLE": true,
    "PRICE_UPDATES_PER_HOUR": 1
  },
  "CORE_RPC": {
    "HOST": "127.0.0.1",
    "PORT": 8332,
    "COOKIE": true,
    "COOKIE_PATH": "/data/bitcoin/.cookie"
  },
  "ELECTRUM": {
    "HOST": "127.0.0.1",
    "PORT": 50001,
    "TLS_ENABLED": false
  },
  "DATABASE": {
    "ENABLED": true,
    "HOST": "127.0.0.1",
    "PORT": 3306,
    "DATABASE": "mempool",
    "USERNAME": "mempool",
    "PASSWORD": "YourPasswordM"
  },
  "SOCKS5PROXY": {
    "ENABLED": false
  },
  "STATISTICS": {
    "ENABLED": true,
    "TX_PER_SECOND_SAMPLE_PERIOD": 150
  }
}
CONFIG

INDEXING_BLOCKS_AMOUNT: 0 disables historical address indexing on first run. Once the node is stable, raise it to 4320 (30 days) or 11000 (about 3 months) to unlock address balance history in the UI. Restart the service after changing it.

Build the backend

Build time: 10-20 minutes

npm install triggers a Rust compilation before installing Node.js packages. On a Pi 5 that takes 5-10 minutes. Run the commands in a tmux or screen session.

Switch to the mempool user:

sudo su - mempool

Move into the backend directory:

cd ~/mempool/backend

Install production dependencies (this is where Rust compiles GBT):

npm install --prod

Build the TypeScript backend:

npm run build

Drop back to admin:

exit

Build the frontend

Build time: 20-30 minutes

Run in the same tmux or screen session. A dropped SSH connection would abort the build.

Switch to the mempool user:

sudo su - mempool

Move into the frontend directory:

cd ~/mempool/frontend

Install dependencies:

npm install

Generate the theme bundle:

npm run generate-themes

Generate the runtime config:

npm run generate-config

Build the Angular app in production mode (English locale only):

npm run ng -- build --configuration production

Copy static assets into the build output:

npm run sync-assets

Drop back to admin:

exit

The built frontend lands in ~/mempool/frontend/dist/mempool/browser.

Why not npm run build?

The standard build script compiles all 33 translation locales, which takes several hours on a Pi. The commands above build only the English source locale and produce the same result.

Autostart on boot

Back as user admin, create the service file:

sudo nano /etc/systemd/system/mempool.service

Paste:

# RaspiBolt: systemd unit for Mempool
# /etc/systemd/system/mempool.service

[Unit]
Description=Mempool Bitcoin Explorer
After=network.target bitcoind.service electrs.service mariadb.service

[Service]
WorkingDirectory=/home/mempool/mempool/backend
ExecStart=/usr/bin/node --max-old-space-size=2048 dist/index.js
User=mempool
Restart=on-failure
RestartSec=60
PrivateTmp=true
ProtectSystem=full
NoNewPrivileges=true
PrivateDevices=true

[Install]
WantedBy=multi-user.target

Enable the service so it starts on boot:

sudo systemctl enable mempool

Start it now:

sudo systemctl start mempool

Follow the log:

sudo journalctl -f -u mempool

Wait for a line containing Listening on http://127.0.0.1:8999/. On first start, Mempool syncs its database from Electrs and Bitcoin Core. Expect 30-60 minutes before fee charts and address lookups populate fully.

Press Ctrl-C to stop following the log.

HTTPS on the LAN with Caddy

Add a Mempool block to the Caddyfile (create the file first if Caddy was not already installed from the BTC RPC Explorer guide):

Open the Caddyfile:
```
sudo nano /etc/caddy/Caddyfile
```

Add the Mempool block after your existing blocks:

# Mempool Explorer
:4080 {
  tls internal

  handle /api/* {
    reverse_proxy localhost:8999
  }

  handle {
    root * /home/mempool/mempool/frontend/dist/mempool/browser
    try_files {path} /index.html
    file_server
  }
}

The /api/* block proxies API calls to the backend. Everything else is served as a static file, falling back to index.html so Angular's client-side routing works for deep links.

Open the firewall port:

sudo ufw allow 4080/tcp comment 'Mempool Explorer (Caddy)'

Reload Caddy so it picks up the new block:

sudo systemctl reload caddy

Point your browser at https://raspibolt.local:4080. Accept the one-time certificate warning.

Main takeaway: you now have a private Bitcoin block explorer and mempool visualizer. The node's own Electrs index answers every query.

Upgrade

Read the release notes before upgrading; some releases include a database migration.

sudo systemctl stop mempool

Switch to the mempool user:

sudo su - mempool

Move into the source tree:

cd ~/mempool

Fetch the latest tags:

git fetch

Check out the new release tag (replace <new-version> with the actual tag):

git checkout v<new-version>

Drop back to admin:

exit

Rebuild the backend. Switch to the mempool user:

sudo su - mempool

Move into the backend directory:

cd ~/mempool/backend

Refresh production dependencies:

npm install --prod

Build the backend:

npm run build

Drop back to admin:

exit

Rebuild the frontend. Switch to the mempool user:

sudo su - mempool

Move into the frontend directory:

cd ~/mempool/frontend

Refresh dependencies:

npm install

Regenerate the theme bundle:

npm run generate-themes

Regenerate the runtime config:

npm run generate-config

Rebuild the Angular app in production mode:

npm run ng -- build --configuration production

Copy static assets into the build output:

npm run sync-assets

Drop back to admin:

exit

Start the service:

sudo systemctl start mempool

Confirm it's running by skimming the recent log:

sudo journalctl -u mempool --since "5 minutes ago"

Uninstall

Stop the service:

sudo systemctl stop mempool

Disable it so it won't start on boot:

sudo systemctl disable mempool

Remove the unit file:

sudo rm /etc/systemd/system/mempool.service

Drop the firewall rule:

sudo ufw delete "allow 4080/tcp"

Remove the Mempool block from /etc/caddy/Caddyfile, then reload:

sudo systemctl reload caddy

Drop the database and user:

sudo mysql <<'SQL'
DROP DATABASE mempool;
DROP USER 'mempool'@'localhost';
SQL

If MariaDB is no longer needed, remove the packages:

sudo apt remove --purge mariadb-server mariadb-client

Then drop any dependencies that are now unused:

sudo apt autoremove

Remove the user:

sudo deluser mempool

Delete its home directory:

sudo rm -rf /home/mempool

Mempool Explorer

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