rumdl

rumdl is a high-performance Markdown linter and formatter that helps ensure consistency and best practices in your Markdown files. Inspired by ruff 's approach to Python linting, rumdl brings similar speed and developer experience improvements to the Markdown ecosystem.

Key Features:

Built for speed with Rust - significantly faster than alternatives
57 lint rules covering common Markdown issues
Automatic formatting with --fix for files and stdin/stdout
Zero dependencies - single binary with no runtime requirements
Highly configurable with TOML-based config files
Multiple installation options - Rust, Python, standalone binaries
Installable via pip for Python users
Modern CLI with detailed error reporting
CI/CD friendly with non-zero exit code on errors

rumdl documentation

Configuration in MegaLinter

Enable rumdl by adding MARKDOWN_RUMDL in ENABLE_LINTERS variable
Disable rumdl by adding MARKDOWN_RUMDL in DISABLE_LINTERS variable

Enable autofixes by adding MARKDOWN_RUMDL in APPLY_FIXES variable

Variable	Description	Default value
MARKDOWN_DEFAULT_STYLE	For rumdl to be active, MARKDOWN_DEFAULT_STYLE must be `rumdl`	`markdownlint`
MARKDOWN_RUMDL_ARGUMENTS	User custom arguments to add in linter CLI call Ex: `-s --foo "bar"`
MARKDOWN_RUMDL_COMMAND_REMOVE_ARGUMENTS	User custom arguments to remove from command line before calling the linter Ex: `-s --foo "bar"`
MARKDOWN_RUMDL_FILTER_REGEX_INCLUDE	Custom regex including filter Ex: `(src\\|lib)`	Include every file
MARKDOWN_RUMDL_FILTER_REGEX_EXCLUDE	Custom regex excluding filter Ex: `(test\\|examples)`	Exclude no file
MARKDOWN_RUMDL_CLI_LINT_MODE	Override default CLI lint mode - `file`: Calls the linter for each file - `list_of_files`: Call the linter with the list of files as argument - `project`: Call the linter from the root of the project	`list_of_files`
MARKDOWN_RUMDL_FILE_EXTENSIONS	Allowed file extensions. `"*"` matches any extension, `""` matches empty extension. Empty list excludes all files Ex: `[".py", ""]`	`[".md"]`
MARKDOWN_RUMDL_FILE_NAMES_REGEX	File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files Ex: `["Dockerfile(-.+)?", "Jenkinsfile"]`	Include every file
MARKDOWN_RUMDL_PRE_COMMANDS	List of bash commands to run before the linter	None
MARKDOWN_RUMDL_POST_COMMANDS	List of bash commands to run after the linter	None
MARKDOWN_RUMDL_UNSECURED_ENV_VARIABLES	List of env variables explicitly not filtered before calling MARKDOWN_RUMDL and its pre/post commands	None
MARKDOWN_RUMDL_CONFIG_FILE	rumdl configuration file name Use `LINTER_DEFAULT` to let the linter find it	`.rumdl.toml`
MARKDOWN_RUMDL_RULES_PATH	Path where to find linter configuration file	Workspace folder, then MegaLinter default rules
MARKDOWN_RUMDL_DISABLE_ERRORS	Run linter but consider errors as warnings	`true`
MARKDOWN_RUMDL_DISABLE_ERRORS_IF_LESS_THAN	Maximum number of errors allowed	`0`
MARKDOWN_RUMDL_CLI_EXECUTABLE	Override CLI executable	`['rumdl']`

IDE Integration

Use rumdl in your favorite IDE to catch errors before MegaLinter !

	IDE	Extension Name	Install
	Visual Studio Code	rumdl - Markdown Linter

MegaLinter Flavors

This linter is available in the following flavors

Flavor	Description	Embedded linters
all	Default MegaLinter Flavor	132
c_cpp	Optimized for pure C/C++ projects	58
cupcake	MegaLinter for the most commonly used languages	90
documentation	MegaLinter for documentation projects	51
dotnet	Optimized for C, C++, C# or VB based projects	66
dotnetweb	Optimized for C, C++, C# or VB based projects with JS/TS	75
formatters	Contains only formatters	19
go	Optimized for GO based projects	53
java	Optimized for JAVA based projects	56
javascript	Optimized for JAVASCRIPT or TYPESCRIPT based projects	61
php	Optimized for PHP based projects	56
python	Optimized for PYTHON based projects	67
ruby	Optimized for RUBY based projects	52
rust	Optimized for RUST based projects	52
salesforce	Optimized for Salesforce based projects	58
swift	Optimized for SWIFT based projects	52
terraform	Optimized for TERRAFORM based projects	56

Behind the scenes

How are identified applicable files

File extensions: .md

How the linting is performed

rumdl is called once with the list of files as arguments (list_of_files CLI lint mode)

Example calls

rumdl check myfile.md

rumdl check --fix myfile.md

rumdl check --fix myfile.md myfile2.md myfile3.md

Help content

A fast Markdown linter written in Rust (Ru(st) MarkDown Linter)

Usage: rumdl [OPTIONS] <COMMAND>

Commands:
  check    Lint Markdown files and print warnings/errors
  fmt      Format Markdown files (alias for check --fix)
  init     Initialize a new configuration file
  rule     Show information about a rule or list all rules
  explain  Explain a rule with detailed information and examples
  config   Show configuration or query a specific key
  server   Start the Language Server Protocol server
  schema   Generate or check JSON schema for rumdl.toml
  import   Import and convert markdownlint configuration files
  vscode   Install the rumdl VS Code extension
  clean    Clear the cache
  version  Show version information
  help     Print this message or the help of the given subcommand(s)

Options:
      --color <COLOR>    Control colored output: auto, always, never [default: auto] [possible values: auto, always, never]
      --config <CONFIG>  Path to configuration file
      --no-config        Ignore all configuration files and use built-in defaults
      --isolated         Ignore all configuration files (alias for --no-config)
  -h, --help             Print help
  -V, --version          Print version

Installation on mega-linter Docker image

Dockerfile commands :

# renovate: datasource=pypi depName=rumdl
ARG RUMDL_MYPY_VERSION=0.0.200

PIP packages (Python):
- rumdl==0.0.200