Configuration Reference

Configuration Reference

CLI flags

Flag	Short	Type	Default	Description
--license	-l	string	MIT	SPDX identifier. Any value is accepted; built-in templates exist for common ones.
--author	-a	string	—	Copyright holder name. Empty string omits the author from the header.
--year	-y	int	current year	Copyright year. Defaults to time.Now().Year() if 0.
--template	-t	string	—	Path to a custom Go template file. Overrides the built-in template for the chosen licence.
--ignore	-i	string	see below	Comma-separated glob patterns to skip. Merged with the default list.
--check	-c	bool	false	Check mode. No files are modified. Exits 1 with a list of missing files if any are unlicensed.
--remove	-R	bool	false	Strip existing license headers. Only removes blocks containing SPDX-License-Identifier or copyright.
--update	-u	bool	false	Replace existing headers (--remove + inject). Canonical migration workflow.
--dry-run	-n	bool	false	Preview changes without writing to disk. Prints [dry-run] would-add/remove/update: <path>.
--verbose	-v	bool	false	Print every file, including already-licensed ones (skipped / ok).
--quiet	-q	bool	false	Suppress all stdout. Errors still go to stderr.
--format	-f	string	text	Output format: text or json (JSON Lines: {"file":"…","status":"…","error":"…"}).
--workers		int	runtime.NumCPU()	Number of parallel goroutines for file processing.
--reuse	-r	bool	false	REUSE/FSFE mode. Emits SPDX-FileCopyrightText: instead of Copyright. Also available in config file.
--version				Prints version, commit, and build date.

Mutually exclusive flag combinations

Combination	Error
--verbose + --quiet	--verbose and --quiet are mutually exclusive
--check + --remove	--check cannot be combined with --remove or --update
--check + --update	--check cannot be combined with --remove or --update
--remove + --update	--remove and --update are mutually exclusive; --update implies removal

Default ignore list

vendor
node_modules
.git
dist
build
*.pb.go
*.gen.go

Additional patterns are added via --ignore or the ignore key in the config file.

Config file

addlicense auto-detects a config file in priority order (first match wins):

1. .addlicenserc.yaml
2. .addlicenserc.yml
3. .addlicenserc.json
4. addlicense.json

The file is resolved relative to the first path argument, then the working directory.

CLI flags always override the config file.

YAML schema

# .addlicenserc.yaml
license: MIT           # string — SPDX identifier
author: Acme Corp      # string — copyright holder
year: 2026             # int — copyright year (defaults to current year)
reuse: false           # bool — emit SPDX-FileCopyrightText: instead of Copyright
ignore:                # list of glob patterns (merged with defaults)
  - vendor
  - node_modules
  - "*.gen.go"
  - "third_party/**"

JSON schema

{
  "license": "MIT",
  "author": "Acme Corp",
  "year": 2026,
  "ignore": ["vendor", "node_modules", "*.gen.go"]
}

Priority rules

Setting	Resolution
license	CLI flag wins, then config file, then default MIT
author	CLI flag wins, then config file, then empty string
year	CLI flag wins, then config file, then time.Now().Year()
ignore	CLI --ignore replaces the config list entirely (not merged)
--check	CLI only — not available in config file
reuse	CLI --reuse wins; config reuse: true sets it when flag is not passed

Custom template

The --template flag accepts a path to a file containing a Go text/template string. The template is rendered with the header.Data struct:

type Data struct {
    Year          int    // copyright year
    Author        string // copyright holder (empty if not set)
    License       string // raw identifier as passed by the user
    SPDX          string // upper-cased identifier
    CopyrightLine string // pre-formatted: "Copyright 2026 Author"
                         // or "SPDX-FileCopyrightText: 2026 Author" with --reuse
}

Example custom template:

{{.CopyrightLine}}
SPDX-License-Identifier: {{.SPDX}}
This file is part of the Acme project.

The template is wrapped in the appropriate comment style for the file type. You do not need to add comment prefixes (//, #, etc.) — addlicense handles that.

Dogfooding

The repo itself uses .addlicenserc.yaml:

license: MIT
author: Grégoire Favreau
ignore:
  - vendor
  - node_modules
  - .git
  - "*.pb.go"
  - "*.gen.go"

The license-check CI workflow runs addlicense --check . on every push to verify all source files are licensed.