Read data from Fallout 3 ESM files.

binary, ESM, Fallout, reader, stream
npm install esm_reader@0.4.0


Read Fallout 3 ESM files

Please note: This is a work in progress. It is only partially implemented and barely tested. Come back later.

This package parses the *.esm data files used by Fallout 3 and exposes the data as Objects via a Node.js Stream.

Another aim of this project is to provide documentation of the file format.


Add this as a dependency to your project:

npm install esm_reader --save

File structure and parsers

Values are stored in little endian format. This controls the Node Buffer methods to use.

Files always start with a TES4 record.

The rest of the file is divided into groups, described next.

parser/ switches to the appropriate parser based on the current state.

Groups parses the start of each group.

The rest of the group is made up of records, described next.

Records parses the start of each record.

The rest of the record is made up of fields, described next.

Fields parses field data from a Buffer.

A field contains a 4 byte label and then 2 bytes indicating the size of the field data. The remaining bytes store the value of the field.

Fields can contain different types of values: text, numbers, bit flags, or lists of those. The type of the value are not described by the field, but rather determined by the labels of the group+record+field.