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Fast Dat Parser

Fast Dat Parser is a C++ command-line utility for streaming Bitcoin Core blk*.dat files into raw block headers, scripts, transaction counts, and output height-and-value data. Its companion bestchain tool filters headers to the best chain.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Fast Dat Parser — OpenViST project profile in Explorers & Analytics.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use it when your analysis starts from local Bitcoin Core blk*.dat files and you need streamed raw data rather than a hosted explorer interface.

Who it is for

  • Developers and analysts working with local Bitcoin block files.
  • Users building offline workflows for inspecting scripts, headers, transaction counts, or output values.

Documented uses

  • Extract block headers or scripts from local Bitcoin data files.
  • Count transactions, inputs, and outputs.
  • Produce output height-and-value records for downstream analysis.
  • Filter headers to the best chain before using a whitelist to exclude other blocks.
Before you choose

Requirements & limits

The repository declares an MIT license. The README warns that the project is not actively maintained.

  • Requires local block data and the parser tools; the documented examples use shell pipelines.
  • Transforms write raw binary output rather than hexadecimal.
  • Orphan blocks are included unless excluded with a whitelist.
  • The README exposes thread, memory, transform, and whitelist options.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Extract scripts from the local best-chain blockchain data

Use the documented parser pipeline to filter block headers into a best-chain whitelist, then export scripts for those blocks.

Before you start

  • Local Bitcoin Core block files matching ~/.bitcoin/blocks/blk*.dat.
  • The parser and bestchain CLI tools available in the working directory.

Steps

  1. Pipe the block files into parser with transform -t0 to output unordered 80-byte block headers, then pipe those headers into bestchain and save the whitelist as chain.dat: cat ~/.bitcoin/blocks/blk*.dat | ./parser -t0 | ./bestchain > chain.dat.

  2. Pipe the block files into parser with -j4 -t1 -wchain.dat and redirect standard output to ~/.bitcoin/scripts.dat: cat ~/.bitcoin/blocks/blk*.dat | ./parser -j4 -t1 -wchain.dat > ~/.bitcoin/scripts.dat.

Expected outcome

A `chain.dat` best-chain filter file and a `scripts.dat` file containing scripts from the filtered blocks, with each script prefixed by a uint16_t length.

Guide limitations

  • The project warns that it is not actively maintained and should be used with caution.
  • Parser transform output is raw binary, not hex.
  • The parser skips bitcoind-allocated zero-byte gaps and includes orphan blocks unless a whitelist omits them.
  • The documented pipeline assumes the named block-file path and parser tools are available; build or installation steps are not documented.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
Source record details
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Sources checked
17 October 2026
Original website title
bitcoinjs/fast-dat-parser · Official homepage title · retained in its source language
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