Bitcoin Core Indexes

Bitcoin Core Indexes

Three optional indexes (in addition to the always-on UTXO set):

txindex

txindex=1

Maps every txid to its block / position. Enables:

• getrawtransaction <txid> for any historical tx (without txindex, only mempool + recent blocks since restart).

Cost:

• Disk: ~80 GB.
• IBD time: +20-50% if enabled from start.
• Rebuild from scratch on a synced node: hours, not days.

When to enable:

• Block explorers / public APIs.
• Forensic / compliance tools.
• Apps that need to look up arbitrary historical txs.

When to skip:

• Pruned nodes (cannot combine).
• Node that only serves recent activity (mempool + last few blocks).

blockfilterindex (BIP157/158)

blockfilterindex=1
peerblockfilters=1   # serve filters to peers

Maintains compact block filters per block. Enables:

• getblockfilter <blockhash> RPC.
• Serving filters to BIP157 clients (Neutrino in LDK / btcwallet).
• Used by Electrs for fast scan operations.

Cost:

• Disk: ~6 GB total.
• IBD impact: +5-10%.

When to enable:

• Running Electrs / Fulcrum / similar indexers (they need it).
• Lightning node using LDK / Neutrino backend.
• Provides scan service to lightweight clients.

coinstatsindex

coinstatsindex=1

Maintains rolling stats for gettxoutsetinfo (UTXO set value, count, hash) without a full scan.

Cost:

• Disk: ~1 GB.
• IBD impact: +2-5%.

When to enable:

• Frequent calls to gettxoutsetinfo (without it, the call takes minutes and locks the wallet).

Without it, gettxoutsetinfo still works but does a full scan on-demand → slow.

Combining

All three can be enabled together. Pruning prevents only txindex.

Typical configurations:

Rebuilding

Adding txindex=1 to existing node:

# Stop node
bitcoin-cli stop
# Edit conf, add txindex=1
# Restart; node rebuilds index
bitcoind -daemon
# Watch
tail -f ~/.bitcoin/debug.log

Output:

2025-... reindex-chainstate already=true txindex=true blockfilterindex=true coinstatsindex=true
2025-... Building txindex
... (hours later) ...
2025-... txindex is enabled

To force rebuild from scratch: -reindex (full reindex, days) or -reindex-chainstate (UTXO + indexes only, hours).

Index storage

• <datadir>/indexes/txindex/ — LevelDB.
• <datadir>/indexes/blockfilter/basic/ — filter files.
• <datadir>/indexes/coinstats/ — LevelDB.

Common bugs

• Adding txindex=1 to a pruned node → bitcoind exits.
• Removing txindex from conf → bitcoind warns but continues with index "stuck"; manually delete indexes/txindex/ to free disk.
• Electrs/Fulcrum not connecting → check peerblockfilters=1 and blockfilterindex=1 are both set.

See also

• operations/SKILL.md
• rpc/SKILL.md
• ../../infrastructure/electrs/SKILL.md
• ../../infrastructure/fulcrum/SKILL.md