# Why blockspace is scarce

The fixed weight limit is the fact; what limits blockspace underneath it is Blockspace Value Theory's argument, labelled as theory.

URL: https://blockspace.wiki/basics/why-blockspace-is-scarce/

> Theory, not fact. Blockspace Value Theory is a living document and an untested thesis. BTP and BYTES are drafts describing things that do not exist.

Every [block](https://blockspace.wiki/glossary/block/) has a fixed capacity, and a byte that is in a block stays in it. Those two facts make [blockspace](https://blockspace.wiki/glossary/blockspace/) limited. Why the limit sits where it does, and what it protects, is argued by [Blockspace Value Theory](https://blockspace.wiki/glossary/bvt/), a living document and an untested thesis. This page keeps the two apart.

## The fact: a fixed limit

Consensus caps every block at 4,000,000 [weight units](https://blockspace.wiki/glossary/weight-unit/). block.space's data-types reference states it as "the 4,000,000 WU consensus block limit". No block may exceed it, so transactions compete for the space. block.space's front page puts the result in one line: "A block is a fixed quantity of blockspace, consumed once and never again."

How much of the chain's space the tokens [BTI](https://blockspace.wiki/glossary/bti/) measures have used: [Book A](https://blockspace.wiki/glossary/book-a/) attributes 133.75 GB of the 777.06 GB in its range, 17.21 % (as of block 972,299, 2026-10-20 09:30:48 UTC).

## What BVT proposes

**What blockspace is.** BVT calls blockspace "a socially constructed commodity built on top of a protocol-enforced constraint". The constraint is real; the commodity is "a useful fiction" that lets markets form. It says this explains "why supply is perfectly inelastic".

**What really limits it.** BVT argues that the binding limit is not bytes per block but "the largest the blockchain could grow while still keeping verification decentralized". Every byte in a block raises, slightly, the cost of running a node that verifies the chain. As that cost rises, fewer people run nodes. On this reading, blockspace value "is therefore, at bottom, the value of keeping verification decentralized". See [decentralization constraint](https://blockspace.wiki/glossary/decentralization-constraint/).

**Why the number can move.** BVT calls the 4M weight limit "a social variable, not a constant", defended "by norms rather than by mathematics", and notes it has "already been fought over once". It contrasts this with bitcoin's own supply: "The 21 million cap is enforced by every validating node rejecting inflationary blocks." The blockspace ceiling is enforced the same way, it says, but its number "is far more contested".

**Why supply is not a schedule.** A full block of witness data approaches 4 MB, and BVT works out that 4 MB × 144 blocks a day × 365 days is about 210 GB a year. It calls that a ceiling, not a schedule: actual use "is demand-determined and has been far below the ceiling". See [halvings and the subsidy](/basics/halvings-and-the-subsidy/) for the comparison with bitcoin's issuance that BVT withdrew.

## Open questions

blockspacelabs.com lists "Blockspace expansion policy" as a descriptive study of the levers that change how much blockspace is usable: the fee floor, the standard size, data-carrier limits, full-RBF, the block weight limit and the witness discount. It "takes no side". The full theory, with its own falsifiable test, is on [Blockspace Value Theory](/concepts/blockspace-value-theory/).

Sources:

- block.space docs: data types · https://block.space/docs/datatypes
- block.space docs: Blockspace Value Theory · https://block.space/docs/bvt
- block.space live pages (/, /rankings, /leaderboard, /largest-inscriptions, /heaviest-tokens, /collections, /sync) · https://block.space
- The blockspacelabs.com page (index.html) · https://blockspacelabs.com
- block.space meter and summary APIs · https://block.space/api/summary

Live figures: books as of block 972,299, 2026-10-20 09:30:48 UTC

Updated: 2026-10-20