The config object

Use this reference to look up exact keys and allowed values. To build a project, start with the step-by-step tutorial, visual field guide, or illustrated cookbook.

These tables are generated from the published JSON Schema. They describe the configuration structure; MLabel also checks relationships such as copied field types and shortcut conflicts when loading a file.

Top-level settings

Key	Type	Required	Notes
$schema	string	no	Path or URL to this JSON Schema, for editor autocomplete. Use https://mlabel.vlad.gg/mlabel.schema.json for a standalone config.
version	2	yes	Config format version. This build reads version 2 only; a config with no version, or a different one, is rejected with a single clear message rather than a cascade of shape errors.
ui	object	no	Chrome-level presentation.
network	object	no	Network policy. Set updateChecks to false to forbid network requests.
input	object	yes	What is read from the source file and shown read-only.
output	object	yes	What the labeler captures, or the app fills in.

ui

Chrome-level presentation.

Key	Type	Required	Notes
appTitle	string | object	no	The window title: a literal string, or { "field": "…" } to use the value of an input field, which changes per record.

network

Network policy. Set updateChecks to false to forbid network requests.

Key	Type	Required	Notes
updateChecks	boolean	no	Whether to check GitHub Releases for updates. Absent or true means checks run; false forbids that traffic entirely.

input

What is read from the source file and shown read-only.

Key	Type	Required	Notes
adapterId	string	no	Which format adapter handles this side. csv is the only one built in; it also reads .tsv. min length 1
adapterConfig	object	no	Opaque, adapter-owned options — for CSV, delimiter and quoteChar on input, delimiter and newline on output. The core never reads this, so it is the one object in the config where unknown keys are allowed.
fields	array of InputField	yes	The source columns to read and show read-only. at least 1 item
rules	array of DisplayRule	no	Purely visual rules over displayed input values. A rule can never change what is exported.
cards	array of Card	no	Layout. Omit for one implicit card holding every field, one per row.

output

What the labeler captures, or the app fills in.

Key	Type	Required	Notes
adapterId	string	no	Which format adapter handles this side. csv is the only one built in; it also reads .tsv. min length 1
adapterConfig	object	no	Opaque, adapter-owned options — for CSV, delimiter and quoteChar on input, delimiter and newline on output. The core never reads this, so it is the one object in the config where unknown keys are allowed.
fields	array of OutputField	yes	The columns written to the output file. at least 1 item
cards	array of Card	no	Layout. Omit for one implicit card holding every field, one per row.

Tip

Point your config’s $schema at https://mlabel.vlad.gg/mlabel.schema.json for autocomplete and inline validation in any editor that understands JSON Schema.