What is GoMeta?
GoMeta.jl is an interpretable-metadata engine, written in Julia, designed to work between, behind and within your data: in any programming language and any file format. The idea is to embed formalized metadata within all kinds of comments and to enable Extensions to act on GoMeta's output. The JuliaCon 2026 proposal puts it this way: "The core concept remains the same: Add interpretable meaning to comments within a Julia file by means of brief, simple, expressive and extendable metadata. The crux of the idea lies in its potential to serve a wider variety of different packages and even facilitating interactions between them." — "However, in order to truly fulfill what had been promised, in particular to allow for the desired expressiveness and extensibility, language-like features had to be incorporated in the proposed schema." A file carries its ordinary content plus #~ metaLines — comment lines with machine-interpretable metadata (e.g. labels, visibility actions, conditions, etc.) sitting right beside the content they describe. GoMeta evaluates the metadata — more precisely, the GoMeta Engine evaluates it — but does not act on those evaluations: that is the Extensions' role; they receive the evaluations through GoMeta's interface, altValues_evals.
The JuliaCon 2026 talk explains GoMeta by asking and answering three questions. This page answers the first — what GoMeta is. Why use GoMeta? answers the second, and How does GoMeta work? the third.
The idea
Embed formalized meaning — metadata — into comments: brief, simple, expressive and extendable metadata, riding where every language already has room for a comment — see Embedding in all kinds of formats.
Absorb and evaluate. GoMeta absorbs that metadata — parses and interprets it — and evaluates which value of which Alterant applies to each piece of the file. Two main products come out of one run: the BLS Component tree — the file as BLS, GoMeta's parser, recorded it — and the evaluated Alterant values,
altValues_evals.Pass the evaluations on to the Extensions, which act on them. An Extension — a renderer, an Extension that produces a notebook or documentation, a program of your own — reads the two products through GoMeta's public surface and executes the task it was designed for. Extensions are so called because they extend the core of GoMeta. The package ships a basic renderer as a development tool for looking at a run — strictly speaking no Extension, though it behaves like one: it lives under the package's development tools, and it is there because it serves a vital purpose for the package's development.
A language and a framework
In the words of the JuliaCon 2026 talk: "On the one hand, GoMeta is a domain specific language for metadata and on the other a framework with facilities on which Extensions can build." The language is the notation of the metaLines (e.g. statements, labels, conditions, the meta hierarchy, etc.) written in the comments of an ordinary file; the Syntax & semantics page is its reference. The framework is the one run that reads a file and delivers the two main products, and the public surface through which the Extensions read them; How does GoMeta work? follows that run, and the Public API page names what a program calls.
Status
GoMeta was presented and released at JuliaCon 2026 by its creator, Jerae Sieburgh; in the words of the talk proposal, the package "finally implements a vastly matured offspring of a [my] half-baked idea proposed at JuliaCon2025." GoMeta.jl 0.4.5 is alpha: a working, tested engine for the v0 subset of the GoMeta language. The sixteen committed example pairs render byte for byte under the shipped test suite, and input the grammar does not accept meets a stable refusal: GoMeta stops with a message that says what it could not accept, and nothing is delivered; a label GoMeta cannot apply — withheld, or not in the vocabulary — does not stop the run: it is reported by a warning diagnostic and the run completes. The surface may still move — by GoMeta's policy, until at least version 0.7 every change of the public surface is a clean cut (no leftover of an older version in a newer one), and the package's API document (docs/public-api.md in the repository) keeps the register of every such change. The language grows by design; the v0 subset forecloses none of it.
GoMeta is Fair Source — licensed under the Functional Source License, Version 1.1, MIT Future License (FSL-1.1-MIT; source-available, not OSI-approved open source): free for everyone's own use — at work, at university, in the public sector — including internal use and access, non-commercial education and research, and professional services provided to other licensees. Not licensed: offering GoMeta to others in a commercial product or service that competes with it or with the Licensor's own GoMeta-based offerings that exist when the version is made available (for that, contact hello@gometa.dev). Each release automatically becomes MIT-licensed on its second anniversary. See the repository for the LICENSE file and details.
From here: Why use GoMeta? — what it is for; How does GoMeta work? — one run, from a file to what the Extensions receive; Embedding in all kinds of formats — where and how the metadata can be embedded; Getting started — the install and one complete run.