Fedimint Bitcoin Wallet

A Bitcoin wallet with fedimint-cli

fedimint-cli lets a single user hold and send Bitcoin through a Fedimint federation. Your balance is real Bitcoin, held on your behalf by the federation's guardians, and you can move it three ways:

• Lightning — send and receive instant Bitcoin payments, brokered by a gateway.
• On-chain — deposit or withdraw ordinary Bitcoin (peg-in / peg-out with the federation's wallet).
• Ecash — hand private bearer notes directly to another person, no third party in the loop.

Under the hood: the balance you hold is Chaumian ecash — private, bearer Bitcoin tokens issued by the federation. Lightning and on-chain are simply ways to convert value into or out of that ecash balance. You mostly don't need to think about this; it's why payments are private and instant.

Setup

1. Install fedimint-cli

Pick the method that matches the platform. On Debian/Ubuntu use the .deb — it is by far the cleanest path. None of these paths require the Nix package manager — the .deb/.rpm/darwin binaries simply bundle their libraries under /nix/store and run without any nix command, daemon, or /nix setup. (Verified on Ubuntu 24.04, Debian 12, and Arch with no Nix installed.)

Debian / Ubuntu (.deb):

apt-get update && apt-get install -y curl                 # if curl is missing (fresh containers)
curl -L -O https://github.com/fedimint/fedimint/releases/download/v0.11.1/fedimint-cli_0.11.1_amd64.deb
apt-get install -y ./fedimint-cli_0.11.1_amd64.deb        # installs to /usr/bin/fedimint-cli
fedimint-cli version-hash                                  # sanity check -> prints a git hash

The .deb is ~170 MB — let the download finish before installing. Installing a truncated file fails with a misleading E: Invalid archive member header. curl -L -O (no progress bar in scripts) gives no hint; check the file size or use curl -fL so a failed download errors instead of half-writing. (Fedora/RHEL: the same page has fedimint-cli-0.11.1-1.x86_64.rpm — dnf install ./…rpm.)

macOS (Apple Silicon): use the prebuilt darwin tarball — no Homebrew/Nix/admin needed, and a curl download isn't Gatekeeper-quarantined so it runs as-is:

curl -fL -O https://github.com/fedimint/fedimint/releases/download/v0.11.1/fedimint-pkgs-v0.11.1-aarch64-apple-darwin.tar.gz
tar xzf fedimint-pkgs-v0.11.1-aarch64-apple-darwin.tar.gz     # -> bin/fedimint-cli (+ bin/fedimintd)
./bin/fedimint-cli version-hash
# If you fetched it via a browser instead of curl, clear the quarantine flag first:
#   xattr -d com.apple.quarantine ./bin/fedimint-cli

Note the macOS/BSD userland lacks GNU niceties: grep -P and the timeout command aren't available (install coreutils via Homebrew for gtimeout, or use jq for JSON extraction below).

NixOS / any system with Nix:

# --accept-flake-config lets Nix use Fedimint's binary cache (fedimint.cachix.org) instead of
# compiling from source — without it the install can take tens of minutes.
nix profile install --accept-flake-config github:fedimint/fedimint/v0.11.1#fedimint-cli
# or run without installing: nix run --accept-flake-config github:fedimint/fedimint/v0.11.1#fedimint-cli -- info

Requires Nix with flakes enabled (experimental-features = nix-command flakes). On NixOS do not use the raw release binary below — an unpatched dynamically-linked binary won't run; use Nix.

Arch / other Linux (no apt/dnf): two nix-free options —

• The bare fedimint-cli-v0.11.1 asset is a self-extracting nix bundle (needs hexdump, tar, xz; pacman -S util-linux xz if missing). It unpacks via nix-user-chroot, so it requires unprivileged user namespaces enabled — on by default on stock Arch/desktop kernels, but blocked in some hardened/container environments (you'll see a "namespace" hint if so; enable it or use the next option).
• Robust (no user namespaces, no dpkg): extract the .deb payload directly — the binary and its bundled libs live under /nix/store, and running them needs no Nix package manager:

  curl -fL -O https://github.com/fedimint/fedimint/releases/download/v0.11.1/fedimint-cli_0.11.1_amd64.deb
  ar x fedimint-cli_0.11.1_amd64.deb && sudo tar -C / -xf data.tar.*     # populates /usr + /nix/store
  sudo ln -sf /nix/store/*-fedimint-cli/bin/fedimint-cli /usr/local/bin/fedimint-cli
  fedimint-cli version-hash
  

Docker: the CLI ships in the fedimintd image:

docker run --rm -v fm-cli-data:/data fedimint/fedimintd:v0.11.1 fedimint-cli --data-dir /data info

2. Pick a data directory

The client stores its keys and database in a data directory. Set it once so every command uses the same wallet — a different data dir is a different, empty wallet.

export FM_CLIENT_DIR="$HOME/.fedimint-cli"       # picked up automatically (same as --data-dir)
mkdir -p "$FM_CLIENT_DIR"

Every command below can also take --data-dir <dir> explicitly. In scripts or any non-interactive setting where each command runs in a fresh shell (so the export above won't persist), pass --data-dir on every invocation instead — otherwise you silently get a fresh, empty wallet.

3. Join a federation

You need an invite code (fed11…) from the federation you want to use.

fedimint-cli join <INVITE_CODE>
fedimint-cli info

info prints the federation id, network, meta fields, and your holdings:

{
  "denominations_msat": { "1": 2, "2": 3, "512": 3, "1024": 3 },
  "federation_id": "c166a596345c126c2cde3fc57e399fec48b1ad741b49dcd48d313cb6cd4458b8",
  "meta": { "federation_name": "Devimint Federation" },
  "network": "regtest",
  "total_amount_msat": 495166,
  "total_num_notes": 41
}

Units — read this, it is the #1 footgun: amounts default to millisatoshis (msat). This includes spend, ln-invoice --amount, and withdraw --amount. A bare number is msat: withdraw --amount 20000 means 20 000 msat = 20 sats, which fails as "under the dust limit". To withdraw 20 000 sats, write --amount 20000000 (msat) or use an explicit unit suffix: --amount '20000 sat' or --amount 0.0002btc. total_amount_msat: 495166 = 495 166 msat ≈ 495 sats. (deposit-address takes no amount — you send BTC to the address from elsewhere.)

Fees: the credited amount is often slightly less than the nominal amount. Reissuing/receiving ecash can incur a small federation mint fee (e.g. reissue of 500 000 msat may credit ~495 000), and receiving Lightning pays the gateway's fee. This is expected, not an error — check info for the actual balance.

Ecash (out-of-band notes)

Ecash is transferred by handing someone a base64 note string. The sender spends (removing the value from their wallet), the receiver reissues (claiming it). Reissue also prevents double-spends.

# Sender: carve out 100 000 msat of notes (selects the smallest note set for the amount)
fedimint-cli spend 100000
# -> {"notes": "BgAAAA…"}   (hand this string to the receiver)

# Receiver: claim the notes into their own wallet.
# NOTE: `spend` returns JSON `{"notes": "BgAAAA…"}` — pass just the inner base64
# string to reissue, not the whole JSON object. Extract it with, e.g.:
#   NOTES=$(fedimint-cli spend 100000 | jq -r .notes)   # then: fedimint-cli reissue "$NOTES"
#   (no jq? portable across GNU/BSD: sed -n 's/.*"notes": *"\([^"]*\)".*/\1/p')
fedimint-cli reissue BgAAAA…
# -> the reissued amount, e.g. 100000

# Check validity WITHOUT claiming (signatures only; does not detect double-spends)
fedimint-cli validate BgAAAA…
# Inspect notes as JSON without touching them
fedimint-cli dev decode notes BgAAAA…

• spend fails if it can't represent the exact amount with available note denominations (notes come in powers of two, so round decimal amounts like 500 000 often can't be made exactly). Add --allow-overpay to send slightly more instead of failing.
• Spent-but-unclaimed notes are auto-reclaimed by the sender after --timeout seconds (default 1 week), so a receiver who never redeems doesn't cost the sender the money permanently.
• Add --include-invite to spend so the receiver can join the federation from the notes alone.

The forward-looking form is fedimint-cli module mint {spend,reissue,split,combine}; the top-level spend/reissue still work and print a deprecation note — either is fine.

Lightning (via a gateway)

Lightning payments are brokered by a gateway. List the gateways the federation knows and, optionally, pick one:

fedimint-cli list-gateways
fedimint-cli switch-gateway <GATEWAY_ID>          # optional; otherwise one is chosen for you

Receive over Lightning

fedimint-cli ln-invoice --amount 100000           # 100 000 msat
# -> {"invoice": "lnbcrt…", "operation_id": "5b37…"}
# Give the "invoice" to the payer, then wait for it to be paid:
fedimint-cli await-invoice 5b37…                  # pass the operation_id
# On success this prints your updated balance JSON (same shape as `info`) and returns.
fedimint-cli info                                 # balance increased

Send over Lightning

fedimint-cli ln-pay "lnbcrt1u1p…"                 # a BOLT11 invoice (or lnurl)

Notes:

• Sending needs enough ecash balance; receiving needs the gateway to have inbound Lightning liquidity.
• If a payment fails, try switch-gateway to a different gateway, or check list-gateways for one that is active.
• The newer LNv2 protocol is under fedimint-cli module lnv2 {receive,send,await-receive,await-send}.

On-chain Bitcoin (peg-in / peg-out)

Deposit (peg-in): on-chain BTC -> ecash

fedimint-cli deposit-address
# -> {"address": "bcrt1q…", "idx": 0, "operation_id": "…"}
# Send BTC to that address from any wallet, then wait for confirmations:
fedimint-cli await-deposit <OPERATION_ID>
fedimint-cli info

Deposits need the federation's finality_delay in confirmations (often ~10 blocks) before the ecash is credited. await-deposit blocks until then, and on success prints a bare null — that is not an error; confirm the credit with info.

Withdraw (peg-out): ecash -> on-chain BTC

fedimint-cli withdraw --amount 50000000 --address bcrt1q…    # 50 000 000 msat = 50 000 sats
fedimint-cli withdraw --amount '50000 sat' --address bcrt1q…  # same, explicit unit
fedimint-cli withdraw --amount all --address bcrt1q…         # sweep everything

The response contains a txid and fees_sat. On regtest the peg-out is broadcast once the federation signs it; mine a block to confirm.

Backup & restore

The client is deterministic from a BIP-39 mnemonic; ecash notes can be recovered by restoring from the federation's encrypted backup.

fedimint-cli print-secret                          # reveals the client's secret — handle carefully
fedimint-cli backup                                # upload encrypted note snapshot to the federation
fedimint-cli restore --mnemonic "word1 word2 …" --invite-code fed11…   # into a fresh data dir

Restore is a scan and can take a while; run fedimint-cli info afterwards to confirm balances.

Quick reference

Common mistakes & troubleshooting

• Empty balance after join: joining does not fund you. You need someone to spend you ecash, a Lightning payment, or an on-chain deposit.
• Wrong wallet: if info shows an unexpected balance, you are almost certainly pointing at a different --data-dir/FM_CLIENT_DIR. Keep it consistent.
• msat vs sats: every --amount (ecash, LN, and on-chain withdraw) defaults to msat. A small bare number on withdraw fails as "under the dust limit" — use <n>000 msat or '<n> sat'.
• spend fails with an amount error: denominations can't represent it exactly — use --allow-overpay.
• Lightning payment fails / no gateway: list-gateways; if the active one is down, switch-gateway to another.
• Deprecation warnings on spend/reissue/ln-invoice/etc. are expected — the commands still work.
• Deposit not credited: on-chain deposits wait for the federation's finality_delay confirmations; keep await-deposit running (on regtest you must mine blocks).
• A killed or contested reissue can wedge the wallet: interrupting reissue, or reissuing notes that were already spent/double-spent, can hang and leave a stuck pending state that makes later commands panic (e.g. Cannot claim input, additional funding needed). Recover by starting over in a fresh --data-dir and re-joining (your on-federation backup can be restored there). Only reissue notes you control and haven't already claimed.
• Discover any subcommand's flags with fedimint-cli help or fedimint-cli <cmd> --help.