# Relay policy

What a node will relay, as opposed to what is valid: the fee floor and sub-1 sat/vB relay, the standard size, data-carrier limits and full-RBF, from Blockspace Holdings' own node.

URL: https://blockspace.wiki/concepts/relay-policy/

Bitcoin has two kinds of rules. Consensus rules decide what is valid in a block. Relay policy decides what a node will pass on to its peers and keep in its mempool before a block is found. block.space's data-types reference puts the difference as "what relays, not what's valid". This page describes the policy settings of [Blockspace Holdings' own Bitcoin node](https://blockspace.wiki/glossary/blockspace-holdings-node-and-indexers/), from its live readings and blockspacelabs.com, and what Blockspace Holdings' documents say about each.

## Blockspace Holdings' node

The live reading of the node's policy (as of block 972,320, 2026-10-20 12:17:53 UTC):

| setting | value |
|---|---|
| node version | /Satoshi:28.2.0/ |
| minrelaytxfee (the fee floor) | 0 sat/vB |
| incrementalrelayfee | 1 sat/vB |
| full-RBF | on |
| maxmempool | 300 MB |

As of 2026-10-20 it is stock Bitcoin Core 28.2.0 with `minrelaytxfee=0`.

## The fee floor and sub-1 sat/vB relay

The [fee floor](https://blockspace.wiki/glossary/fee-floor/) is the lowest [fee rate](https://blockspace.wiki/glossary/fee-rate/) a node will relay. The blockspacelabs.com site describes 1 sat/vB as "the default floor of Bitcoin Core". Blockspace Holdings' node runs with the floor at 0, so it relays and keeps transactions paying less than 1 sat/vB. It held 45,999 transactions, 25.2 MB, at a 0 floor when measured on 2026-10-20.

blockspacelabs.com lists this as a **Live** project, "Sub-1 sat/vB relay", with the node's mempool figures. Its page, as of 2026-10-20 09:07:08 UTC at block 972,298, showed 38,991 transactions in the mempool (23.7 vMB), of which 38,265 paid below 1 sat/vB. The site counts a transaction as sub-1 when its base fee in sats is less than its vsize. Its research card "The sub-1 sat/vB share" gave the share as 98.1 % of transactions at that reading, and proposes a series hour by hour.

The documents record that low rates were not only a relay matter. Blockspace Value Theory's reference data notes "sustained periods at 0.13–0.14 sat/vB, with AntPool accepting sub-1 sat/vB inscriptions" in early to mid 2026.

## Standard transaction size

A [standard transaction](https://blockspace.wiki/glossary/standard-transaction/) may weigh at most 400,000 [WU](https://blockspace.wiki/glossary/weight-unit/), about 100,000 vB. The data-types reference calls this `MAX_STANDARD_TX_WEIGHT` and says a bigger transaction, such as the 3.94 MB Taproot Wizards block it cites, needs direct-to-miner submission. The reference gives the practical ceiling for witness payload in one standard transaction as about 397 kB.

4 MB relay is **not configured**: stock Core 28 treats a transaction over 400,000 WU as non-standard and will not relay it, and relaying 4 MB transactions needs a patched node. It is "just a research project", and blockspacelabs.com lists it as **Research**: "No node here relays 4 MB transactions today."

The data-types reference lists other policy limits, among them:

- P2WSH: at most 100 stack items, 80 bytes per item, and a witnessScript of at most 3,600 bytes;
- tapscript: at most 80 bytes per initial stack item;
- the taproot annex: still non-standard in Bitcoin Core.

It notes that the 80-byte item caps do not constrain inscriptions, because envelope data lives inside the leaf script as pushes of up to 520 bytes (a consensus limit), not in stack items. "That asymmetry is exactly why the envelope pattern won."

## Data-carrier limits

Consensus has never limited OP_RETURN size or count; the size story is entirely relay policy. The data-types reference gives the history: the long-lived default `-datacarriersize=83`, one nulldata output per transaction, and then Bitcoin Core 30.0 (October 2025) raising the default to 100,000 bytes and allowing several OP_RETURN outputs. Blockspace Holdings' node runs Core 28.2, and blockspacelabs.com gives its OP_RETURN limit as 83 bytes, the Core 28 default. The reference also records the 2025 dispute between Core and Knots over these limits, and Knots' smaller default.

## Full-RBF

The node runs with [full-RBF](https://blockspace.wiki/glossary/full-rbf/) on. blockspacelabs.com's research card "Full-RBF in practice" proposes to count the replacements its mempool sees with full-RBF on, and which of them reach blocks. Blockspace Holdings' documents say no more than that about it.

## The research around it

blockspacelabs.com's "Blockspace expansion policy" card describes a study of the levers that change how much blockspace is usable and who can reach it. On the relay side: the fee floor, the standard transaction size, data-carrier limits and full-RBF. On the consensus side: the block weight limit (4,000,000 WU) and the [witness discount](/concepts/witness-discount/). It is written descriptively, "as research rather than advocacy", stating no position the owner has not given. Two related cards, "Policy observatory" and "Low-fee propagation", propose to count mined transactions that standard relay would refuse and to follow which sub-1 sat/vB transactions get mined. They are described studies, with no results yet.

Sources:

- Blockspace Holdings records
- The blockspacelabs.com page (index.html) · https://blockspacelabs.com
- Blockspace Labs facts (data/facts.json) · https://blockspacelabs.com
- block.space docs: data types · https://block.space/docs/datatypes
- Blockspace Value Theory · https://block.space/docs/bvt

Live figures: relay as of block 972,320, 2026-10-20 12:17:53 UTC

Updated: 2026-10-20