4.0.5 • Public • Published


OpenAPI / Swagger / AsyncAPI / Semoasa definition to Slate / ReSlate compatible markdown

Build Tested on APIs.guru Tested on Mermade OpenAPIs Known Vulnerabilities

Widdershins adverb:

  • In a direction contrary to the sun's course;
  • anticlockwise;
  • helping you produce static documentation from your OpenAPI 3.0 / Swagger 2.0 / AsyncAPI 1.x / Semoasa 0.1.0 definition

Widdershins screenshot


  • Version 4.0 changes:
    • Now uses Promises not callbacks
    • Option to output html directly, and to ReSpec format
    • Unified JavaScript and Node.js code-samples, PHP added
    • restrictions column (readOnly/writeOnly) added to schema templates
    • Numerous bug fixes
  • As of v3.0.0 Widdershins no longer expands the definition of OpenAPI body parameters / requestBodies by default, unless they have an inline schema. You can restore the old behaviour by using the --expandBody option.
  • You may limit the depth of schema examples using the --maxDepth option. The default is 10.
  • To omit schemas entirely, please copy and customise the main.dot template.
  • As of v3.1.0 Widdershins includes a generated Authorization header in OpenAPI code samples. If you wish to omit this, see here.

To install

  • Clone the git repository, and npm i to install dependencies, or
  • npm install -g widdershins to install globally

Getting started

Widdershins is generally used as a stage in an API documentation pipeline. The pipeline begins with an API definition in OpenAPI 3.x, OpenAPI 2.0 (fka Swagger), API Blueprint, AsyncAPI or Semoasa format. Widdershins converts this description into markdown suitable for use by a renderer, such as Slate, ReSlate, Shins (deprecated) or html suitable for use with ReSpec.

If you need to create your input API definition, this list of available editors may be useful.

More in-depth documentation is available here.


node widdershins --search false --language_tabs 'ruby:Ruby' 'python:Python' --summary defs/petstore3.json -o petstore3.md


CLI parameter name JavaScript parameter name Type Default value Description
--clipboard options.clipboard boolean true Sets the value of the code_clipboard property in the heading, so that markdown processors can include clipboard support.
--customApiKeyValue options.customApiKeyValue string ApiKey Set a custom API key value to use as the API key in generated code examples.
--expandBody options.expandBody boolean false If a method's requestBody parameter refers to a schema by reference (not with a inline schema), by default, Widdershins shows only a reference to this parameter. Set this option to true to expand the schema and show all properties in the request body.
--headings options.headings integer 2 Set the value of the headingLevel parameter in the header so markdown processors know how many heading levels to show in the table of contents. Currently supported only by Shins, not by Slate, which lacks this feature.
--omitBody options.omitBody boolean false By default, Widdershins includes the body parameter as a row in the parameters table before the rows that represent the fields in the body. Set this parameter to omit that body parameter row.
--omitHeader options.omitHeader boolean false Omit the header / YAML front-matter in the generated Markdown file.
--resolve options.resolve boolean false Resolve external $refs, using the source parameter or the input file as the base location.
--shallowSchemas options.shallowSchemas boolean false When referring to a schema with a $ref, don't show the full contents of the schema.
N/A options.source string None The absolute location or URL of the source file to use as the base to resolve relative references ($refs) from; required if options.resolve is set to true. For CLI commands, Widdershins uses the input file as the base for the $refs.
--summary options.tocSummary boolean false Use the operation summary as the TOC entry instead of the ID.
--useBodyName options.useBodyName boolean Use original param name for OpenAPI 2.0 body parameter.
-v, --verbose options.verbose boolean false Increase verbosity.
-h, --help options.help boolean false Show help.
--version options.version boolean false Show version number.
-c, --code options.codeSamples boolean false Omit generated code samples.
--httpsnippet options.httpsnippet boolean false Use httpsnippet to generate code samples.
-d, --discovery options.discovery boolean false Include schema.org WebAPI discovery data.
-e, --environment N/A string None File to load config options from.
-i, --includes options.includes string None List of files to put in the include header of the output Markdown. Processors such as Shins can then import the contents of these files.
-l, --lang options.lang boolean false Generate the list of languages for code samples based on the languages used in the source file's x-code-samples examples.
--language_tabs options.language_tabs string (Differs for each input type) List of language tabs for code samples using language[:label[:client]] format, such as javascript:JavaScript:request.
-m, --maxDepth options.maxDepth integer 10 Maximum depth to show for schema examples.
-o, --outfile N/A string None File to write the output markdown to. If left blank, Widdershins sends the output to stdout.
-r, --raw inverse of options.sample boolean false Output raw schemas instead of example values.
-s, --search options.search boolean true Set the value of the search parameter in the header so Markdown processors like Slate include search or not in their output.
-t, --theme options.theme string darkula Syntax-highlighter theme to use.
-u, --user_templates options.user_templates string None Directory to load override templates from.
-x, --experimental options.experimental boolean Use httpSnippet for multipart mediatypes.
-y, --yaml options.yaml boolean false Display JSON schemas in YAML format.
options.templateCallback function None A function that is called before and after each template (JavaScript code only).
options.toc_footers object A map of urls and descriptions to be added to the ToC footers array (JavaScript code only).

In Node.JS code, create an options object and pass it to the Widdershins convert function, as in this example:

const converter = require('widdershins');
let options = {}; // defaults shown
options.codeSamples = true;
options.httpsnippet = false;
//options.language_tabs = [];
//options.language_clients = [];
//options.loadedFrom = sourceUrl; // only needed if input document is relative
//options.user_templates = './user_templates';
options.templateCallback = function(templateName,stage,data) { return data };
options.theme = 'darkula';
options.search = true;
options.sample = true; // set false by --raw
options.discovery = false;
options.includes = [];
options.shallowSchemas = false;
options.tocSummary = false;
options.headings = 2;
options.yaml = false;
//options.resolve = false;
//options.source = sourceUrl; // if resolve is true, must be set to full path or URL of the input document
.then(str => {
  // str contains the converted markdown
.catch(err => {

To only include a subset of the pre-defined language-tabs, or to rename their display-names, you can override the options.language_tabs:

options.language_tabs = [{ 'go': 'Go' }, { 'http': 'HTTP' }, { 'javascript': 'JavaScript' }, { 'javascript--node': 'Node.JS' }, { 'python': 'Python' }, { 'ruby': 'Ruby' }];

The --environment option specifies a JSON or YAML-formatted options object, for example:

  "language_tabs": [{ "go": "Go" }, { "http": "HTTP" }, { "javascript": "JavaScript" }, { "javascript--node": "Node.JS" }, { "python": "Python" }, { "ruby": "Ruby" }],
  "verbose": true,
  "tagGroups": [
      "title": "Companies",
      "tags": ["companies"]
      "title": "Billing",
      "tags": ["invoice-create", "invoice-close", "invoice-delete"]

You can also use the environment file to group OAS/Swagger tagged paths together to create a more elegant table of contents, and overall page structure.

If you need to support a version of Slate <v1.5.0 (or a renderer which also doesn't support display-names for language-tabs, such as node-slate, slate-node or whiteboard), you can use the --environment option with the included whiteboard_env.json file to simply achieve this.

If you are using the httpsnippet option to generate code samples, you can specify the client library used to perform the requests for each language by overriding the options.language_clients:

options.language_clients = [{ 'shell': 'curl' }, { 'node': 'request' }, { 'java': 'unirest' }];

If the language name differs between the markdown name required to syntax highlight and the httpsnippet required target, both can be specified in the form markdown--target.

To see the list of languages and clients supported by httpsnippet, click here.

The loadedFrom option is only needed where the OpenAPI / Swagger definition does not specify a host, and (as per the OpenAPI specification) the API endpoint is deemed to be based on the source URL the definition was loaded from.

To see the list of highlight-js syntax highlighting themes, click here.

Schema.org WebAPI discovery data is included if the discovery option above is set true. See the W3C WebAPI Discovery Community Group for more information.

Language tabs

Widdershins supports the x-code-samples vendor-extension to completely customise your documentation. Alternatively, you can edit the default code-samples in the templates sub-directory, or override them using the user_templates option to specify a directory containing your templates.

Widdershins supports the use of multiple language tabs with the same language (i.e. plain Javascript and Node.Js). To use this support you must be using Slate (or one of its ports compatible with) version 1.5.0 or higher.


By default, Widdershins uses the templates in its templates/ folder to generate the Markdown output. To customize the templates, copy some or all of them to a folder and pass their location to the user_templates parameter.

The templates include .dot templates and .def partials. To override a .dot template, you must copy it and the child .def partials that the template references. Similarly, to override a .def partial, you must also copy the parent .dot template. For OpenAPI 3, the primary template is main.dot and its main child partials are parameters.def, responses.def, and callbacks.def.

This means that it is usually easiest to copy all .dot and .def files to your user templates directory so you don't skip a template or partial. To bring in changes from Widdershins updates, you can use a visual diff tool which can run across two directories, such as Meld or WinMerge.

Template syntax

Templates are compiled with doT.js.

Templates have access to a data object with a range of properties based on the document context. For information about the parameters, see the README file for the appropriate templates:

To print the value of a parameter or variable in a template, use the code {{=parameterName}}. For example, to print the title of an OpenAPI 3 spec (from its info.title field), use the code {{=data.api.info.title}}.

To loop through values in an array, use the code {{~ arrayName :tempVariable}} to start the loop and the code {{~}} to close the loop. For example, the OpenAPI 3 partial parameters.def uses this code to create a table of the parameters in an operation:

{{~ data.parameters :p}}|{{=p.name}}|{{=p.in}}|{{=p.safeType}}|{{=p.required}}|{{=p.shortDesc || 'none'}}|

For if/then logic, use the code {{? booleanExpression}} to start the code block and the code {{?}} to close the block. For example, the OpenAPI 3 main.dot template calls the security.def partial to show information about the security schemes if the OpenAPI spec includes a securitySchemes section:

{{? data.api.components && data.api.components.securitySchemes }}

You can run arbitrary JavaScript within a template by inserting a code block within curly braces. For example, this code creates a variable and references it with normal doT.js syntax later in the template:

{{ {
let message = "Hello!";
} }}


Template callbacks

The templateCallback parameter points to a function that Widdershins calls before and after each template runs. The callback function receives a data object that contains the spec that Widdershins is processing; the function must return this object. You can use callback functions only if you are calling Widdershins from JavaScript code, not from the command line.

Widdershins passes these variables to the callback function:

  • templateName: The name of the template, such as main.
  • stage: Whether Widdershins is calling the callback function before (pre) or after (post) the template.
  • data: An object that contains the data that Widdershins is processing. You can mutate the data object in any way you see fit, but the function must return it whether it changes it or not. Content that you put in the data.append property is appended to the current output stream.

For example, this JavaScript code prints the name of the template and the processing stage in the output Markdown:

'use strict';

const converter = require('widdershins');
const fs = require('fs');

let options = {};
options.templateCallback = myCallBackFunction;

function myCallBackFunction(templateName, stage, data) {
  let statusString = "Template name: " + templateName + "\n";
  statusString += "Stage: " + stage + "\n";
  data.append = statusString;
  return data;

const apiObj = JSON.parse(fs.readFileSync('defs/petstore3.json'));

converter.convert(apiObj, options)
.then(str => {
  fs.writeFileSync('petstore3Output.md', str, 'utf8');


To run a test-suite:

node testRunner {path-to-APIs}

The test harness currently expects .yaml or .json files and has been tested against

Comparison between this and other OpenAPI / Swagger to Slate tools

Blog posting by the author of Widdershins.


Widdershins in the wild

Please feel free to add a link to your API documentation here.

Widdershins and ReSlate

  • Widdershins works well with Slate, but for a solely Node.js-based experience, why not try the ReSlate port?

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