# BIP91 activation (SegWit mandate)

> A passage of **The βook of βitcoin** — the Bitcoin chain read as a book. This is
> block 477,120 read as a chapter, and its transaction 1
> (of 129) read as a section of Glossia prose. Every byte of the
> transaction is carried in the prose and decodes back out losslessly; the
> connective grammar is the translator's, the content is the chain's.

- **Citation:** III β29 ■673 §1 (Volume III, Book 29, Chapter 673, section 1)
- **Block:** 477,120 — BIP91 activation (SegWit mandate)
- **Block hash:** `0000000000000000015411ca4b35f7b48ecab015b14de5627b647e262ba0ec40`
- **Transaction id:** `4b777745084ef83da587c7278db17f7a33ad5b831b5ee47b18c1c11c6165047c`
- **Read live:** https://bookofbitcoin.io/bitcoin-book.html?txid=4b777745084ef83da587c7278db17f7a33ad5b831b5ee47b18c1c11c6165047c

## Chapter frontispiece — block 477,120

Block hash, as prose: ⌘¹⁸⁵ *Abuse access to alter via chimney to film. Gun cram an unique sky out its frequent ethics for master. The history never set jet. Tax twice knee steel. Our junk bacon may parade its divorce.* ⓪⁷¹

- **version:** vaccio abandon 10010 — block version 0x20000012 — BIP9 version-bits form; accio abandon — no version rolling; signaling bit 1 — SegWit (BIP141), bit 4
- **previous block:** ⌘¹⁸² Bed may absorb accident to olive. A shaft wrap avocado. Journey cushion our world sun. Pepper tumble each glare. Skull may set glass. Wagon easily see festival. A pay may avoid a hit. ⓪⁷⁴
  - hex: `00000000000000000022552c92fdc5ac6c31a95f54d9ed9fcdf0fe00ff134773`
- **merkle root:** ⋔ Abandon yes account its hungry lip. The jet is casual. Each night is chronic. Its bad return hire poverty. Cap may empower our large faculty. A demand may trip an unhappy yes. Each sir remove theme to judge. An amazing orphan camp rebel. Lamp may middle each image.
  - hex: `8a13a3f9326b1073faa078007fadda8d1e9d46a50f4948055b7087c2ca8ee88d`
- **timestamp:** 2017-07-23 04:46 UTC
- **difficulty target:** β₇₁ < 89564×256²¹ — the block hash above reads below this target — nBits 18015ddc — mantissa 89564 (2²·22391) shifted up 21 bytes: the target 0000000000000000015ddc000000000000000000000000000000000000000000, which a valid block hash must read below (71 leading zero bits) — difficulty 804,525,194,568 (relative to the genesis block)
- **nonce:** η 2·3²·7·13·37·30241

## § 1 — BIP91 activation (SegWit mandate)

Transaction id, as prose: ⌘²⁵⁶ *Abandon ago get its red accident. Tie then bone our season. Slot may set a guy. An they. Giggle set lady to fun. Swing get street via foil. Dash divert shiver to pilot. The shy diamond may exhaust vacuum. A they. Cargo is pop to the tape for a due tea. Bet truly see set.*

- **version:** 1
- **input 1:** coinbase (∅ — no previous output; new coin)
  - script: ■477120 2017-07-23 04:46“/BATPOOL/NYA/” An above acid may sting opera. Surprise might ship struggle. Set depend club over the tie. Our typical oxygen is dizzy. Normal home design slight. The net is civil. Parent far dose coral. Glare set its merry type. Proof out need safe. The acoustic guy may row. ⓪⁷ η2·3·12323·5161630937 ⓪⁵
  - sequence: ● — final — disables the transaction locktime for this input
- **output 1:** 12.55159445 ₿
  - script: ⧉ ⌖ h²⁰ The absurd abuse scale stand. Our lazy soap early brick our match. Sky may idle tuna. Wood patrol swift to token. Pie yet carry scale. ≡ ∇
- **output 2:** 0 ₿
  - script: ¶ ⋔w h³² Abandon out achieve pizza. Audit get glove to enough marriage. Sir may enrich task out venture. Leisure may supply tree. Royal enjoy to deliver for a zero. Company know pepper to tuna per fog. Our blood march friend.
- **locktime:** □ — no locktime — final with respect to time

## Commentary

> A reading of the record, not the record. The passage above is the chain's own
> speech — verifiable byte for byte, no author, public domain. What follows is
> somebody's account of why it is worth reading: editorial, licensed CC BY 4.0,
> and no more authoritative than the argument behind it.

From 22 July 2017 signaling for SegWit was briefly mandatory: a block that did not set bit 1 was rejected, squeezing BIP141 over its own 95% threshold. A transient rule, spent the moment SegWit locked in, and a soft fork all the same — the chain has a few of these, rules that existed only long enough to force a decision.

— Claude Opus 5

---

*Reading the notation:* italic prose passages are Glossia encodings of the raw
bytes (decodable with the [glossia](https://crates.io/crates/glossia) engine,
wordlist `bip39`, language `english`); glyphs are the book's script notation
(opcode and data marks); small structural integers (version, counts, values,
locktime) are printed literally. A block hash reads ⌘ᵐ <prose> ⓪ⁿ — the
m = 256 − n bits of the double-SHA256 (⌘, OP_HASH256), Glossia-encoded as
⌈m/8⌉ bytes, then the n proof-of-work zero bits that follow them in the
internal-order bytes the prose encodes. See
[/llms.txt](https://bookofbitcoin.io/llms.txt) for how any other passage on the chain can be
fetched and read the same way.