Nano Markup

Nano Markup 1.0.0

Structured data,
without the visual noise.

Nano Markup is a minimal, indentation-based format for representing strings, mappings, and sequences in a form designed to be easy for people to read and write.

Read the specification Use Nano Markup

One value, two syntaxes

Readable at a glance

Nano Markup
..
    name Ariana
    languages:
        Slovak
        English
    address|
        20 Forest Street
        811 01 Bratislava
JSON
{
  "name": "Ariana",
  "languages": [
    "Slovak",
    "English"
  ],
  "address": "20 Forest Street\n811 01 Bratislava"
}

Browse practical Nano Markup examples →

The complete data model

Exactly three value types

Aa

String

Unicode text, including empty and multiline text. Nano Markup does not infer numbers, booleans, nulls, or dates.

..

Mapping

An unordered association of unique string keys to values. Mappings may contain strings, mappings, and sequences.

:

Sequence

An ordered collection of values. Items may have different types, and duplicate items are preserved.

Syntax at a glance

A small language on purpose

Root mapping..
Root sequence:
String entryname Ariana
Nested mappingcontact..
Nested sequencelanguages:
Multiline stringaddress|
Comment# comment

Each structural level uses exactly four ASCII spaces. A document can also contain a string directly at its root. The conventional file extension is .nano.

Start using it

Specification and implementations

Why Nano Markup Readable data format Learn where the language fits and why its data model stays small. Nano Markup tutorial Strings · mappings · sequences Start with the basics: indentation, text blocks, comments, and empty values. Language specification Normative grammar, conformance fixtures, examples, and release history. Specification design Rationale See why the language keeps exactly three value types and fixed indentation. Conformance testing Shared corpus Understand how stable implementations prove matching parser and writer behavior. Python implementation Stable 1.0.0 · Python 3.11+ Decode and encode Nano Markup using native Python values. Go implementation Stable 1.0.0 · Go 1.24+ Decode and encode with typed String, Mapping, and Sequence values. JavaScript & TypeScript Stable 1.0.0 · Node.js 22+ · Browsers Parse and stringify with ESM, CommonJS, and first-class types. Dart implementation Stable 1.0.0 · Dart 3.12+ · Web · Flutter Decode and encode using native Dart values across every Dart platform. Java implementation Stable 1.0.0 · Java 17+ Decode and encode using standard Java collections and strings. C# / .NET implementation Stable 1.0.0 · .NET 8+ Decode and encode using idiomatic C# collections and strings. C and C++ implementation Stable 1.0.0 · C11 · C++17 · CMake Decode and encode with a portable C API and C++ wrapper. Rust implementation Stable 1.0.0 · Rust stable Decode and encode with idiomatic Rust values and a validator CLI. Swift implementation Stable 1.0.0 · Swift 6+ Decode and encode with idiomatic Swift values. PowerShell implementation Stable 1.0.0 · PowerShell 7.2+ Decode and encode with idiomatic PowerShell cmdlets.

Compare and install implementations →

Compare formats

Nano Markup beside familiar choices

Nano Markup vs YAML Compare indentation, type inference, advanced features, and configuration use cases. Nano Markup vs JSON See how Nano Markup trades universal interchange for easier plain-text authoring. Nano Markup vs TOML Compare typed configuration tables with a smaller indentation-based data tree. Nano Markup FAQ Short answers about YAML alternatives, JSON comparisons, comments, stability, and implementations.

Stable release

Nano Markup 1.0.0

The first stable language specification was published on July 24, 2026. Stable releases are immutable; any known errors are recorded separately as errata.

Release notes and downloads

About this repository

This repository contains the official Nano Markup website. The normative language specification and conformance suite are maintained in the Nano Markup specification repository. Website corrections and improvements are welcome through pull requests.