NestedText: A Human Friendly Data Format
Authors: Ken & Kale Kundert
Version: 3.5
Released: 2022-11-04
Please post all questions, suggestions, and bug reports to: Github.

NestedText is a file format for holding structured data to be entered, edited, or viewed by people. It organizes the data into a nested collection of dictionaries, lists, and strings without the need for quoting or escaping. A unique feature of this file format is that it only supports one scalar type: strings.  While the decision to eschew integer, real, date, etc. types may seem counter intuitive, it leads to simpler data files and applications that are more robust.

NestedText is convenient for configuration files, address books, account information, and the like. Because there is no need for quoting or escaping, it is particularly nice for holding code fragments. Here is an example of a file that contains a few addresses:

# Contact information for our officers

Katheryn McDaniel:
    position: president
        > 138 Almond Street
        > Topeka, Kansas 20697
        cell: 1-210-555-5297
        home: 1-210-555-8470
            # Katheryn prefers that we always call her on her cell phone.
    additional roles:
        - board member

Margaret Hodge:
    position: vice president
        > 2586 Marigold Lane
        > Topeka, Kansas 20682
    phone: 1-470-555-0398
    additional roles:
        - new membership task force
        - accounting task force

One of the more attractive use-cases for NestedText is command line programs whose output is meant to be consumed by either people or programs. Many programs do so by supporting a --json command-line flag that indicates the output should be computer readable rather than human readable. But, with NestedText it is not necessary to make people choose. Just output the result in NestedText and it can be read by people or computers. For example, consider a program that read your address list and output particular fields on demand:

> address --email
Katheryn McDaniel:
Margaret Hodge:

This could output could be fed directly into another program that accepted input as NestedText:

> address --email | mail-to-list


This package contains a Python reference implementation of NestedText and a test suite. Implementation in many languages is required for NestedText to catch on widely. If you like the format, please consider contributing additional implementations.

Also, please consider using NestedText for any applications you create. It is especially suitable for configuration files.