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Ensuring data privacy

Material for MkDocs makes compliance with data privacy regulations very easy, as it offers a native cookie consent solution to seek explicit consent from users before setting up analytics. Additionally, external assets can be automatically downloaded for self-hosting.

Configuration

8.4.0 · Default: none · Experimental

Material for MkDocs ships a native and extensible cookie consent form which asks the user for consent prior to sending requests to third parties. Add the following to mkdocs.yml:

extra:
  consent:
    title: Cookie consent
    description: >- # (1)!
      We use cookies to recognize your repeated visits and preferences, as well
      as to measure the effectiveness of our documentation and whether users
      find what they're searching for. With your consent, you're helping us to
      make our documentation better.
  1. You can add arbitrary HTML tags in the description, e.g. to link to your terms of service or other parts of the site.

The following properties are available:

title

Default: none · Required – This property sets the title of the cookie consent, which is rendered at the top of the form and must be set to a non-empty string.

description

Default: none · Required – This property sets the description of the cookie consent, is rendered below the title, and may include raw HTML (e.g. a links to the terms of service).

cookies

Default: none – This property allows to add custom cookies or change the initial checked state and name of built-in cookies. Currently, the following cookies are built-in:

  • Google Analytics – analytics (enabled by default)
  • GitHub – github (enabled by default)

Each cookie must receive a unique identifier which is used as a key in the cookies map, and can be either set to a string, or to a map defining name and checked state:

extra:
  consent:
    cookies:
      analytics: Custom name

extra:
  consent:
    cookies:
      analytics:
        name: Google Analytics
        checked: false

extra:
  consent:
    cookies:
      analytics: Google Analytics # (1)!
      custom: Custom cookie
  1. If you define a custom cookie as part of the cookies property, the analytics cookie must be added back explicitly, or analytics won't be triggered.

If Google Analytics was configured via mkdocs.yml, the cookie consent will automatically include a setting for the user to disable it. Custom cookies can be used from JavaScript.

actions

Default: [accept, manage] – This property defines which buttons are shown and in which order, e.g. to allow the user to accept cookies and manage settings:

extra:
  consent:
    actions:
      - accept
      - manage # (1)!
  1. If the manage settings button is omitted from the actions property, the settings are always shown.

The cookie consent form includes three types of buttons:

  • accept – Button to accept selected cookies
  • reject – Button to reject all cookies
  • manage – Button to manage settings

When a user first visits your site, a cookie consent form is rendered:

Cookie consent enabled

In order to comply with GDPR, users must be able to change their cookie settings at any time. This can be done by adding a simple link to your copyright notice in mkdocs.yml:

copyright: >
  Copyright © 2016 - 2023 Martin Donath –
  <a href="#__consent">Change cookie settings</a>

Built-in privacy plugin

Sponsors only · insiders-4.9.0 · Plugin · Experimental

The built-in privacy plugin automatically identifies external assets as part of the build process and downloads all assets for very simple self-hosting. Add the following lines to mkdocs.yml:

plugins:
  - privacy

If you need to be able to build your documentation with and without Insiders, please refer to the built-in plugins section to learn how shared configurations help to achieve this.

The following configuration options are available:

enabled

Default: true – This option specifies whether the plugin is enabled when building your project. If you want to speed up local builds, you can use an environment variable:

plugins:
  - privacy:
      enabled: !ENV [CI, false]
concurrency

Default: number of CPUs – This option specifies how many CPUs the plugin is allowed to use when downloading external assets. With more CPUs, the plugin can do more work in the same time, thus complete its work faster. Concurrent processing can be disabled with:

plugins:
  - privacy:
      concurrency: 1

External assets

The following configuration options are available for external assets:

external_assets

Default: bundle – This option specifies what the plugin should do when encountering external assets. There are two options: while report will issue warning messages during the build, bundle will automatically download all external files and adjust all references:

plugins:
  - privacy:
      external_assets: bundle

If you've removed all external assets from your project via customization, it's still a good idea to enable the plugin and set the mode to report, as the plugin will make sure that there are no hidden external links in any Markdown files that were unintentionally added.

Using report in strict mode will make the build fail when external assets are detected.

external_assets_dir

Default: assets/external – This option specifies where the downloaded external assets will be stored. It's normally not necessary to change this option:

plugins:
  - privacy:
      external_assets_dir: assets/external

The path must be defined relative to docs_dir.

external_assets_include

Default: none – This option allows to only include certain external assets for processing by the privacy plugin, so they will be downloaded and bundled during the build:

plugins:
  - privacy:
      external_assets_include:
        - unsplash.com/*

Hosting images externally and optimizing them automatically

This option makes the built-in privacy plugin an excellent choice for when you want to host assets like images outside of your git repository in another location to keep them fresh and your repository lean.

Additionally, as of insiders-4.30.0, the built-in privacy plugin was entirely rewritten and now works perfectly with the built-in optimize plugin, which means that external assets can be passed through the same optimization pipeline as the rest of your documentation. This means you can store and edit unoptimized files outside of your repository, and let both plugins built a highly optimized site for you.

If you want to implement separate pipelines, i.e., optimize some images differently from others or exclude some images from downloading, you can use multiple instances of the built-in privacy plugin.

external_assets_exclude

Default: none – This option allows to exclude certain external assets from processing by the privacy plugin, so they will not be downloaded and bundled during the build:

plugins:
  - privacy:
      external_assets_exclude: # (1)!
        - cdn.jsdelivr.net/npm/mathjax@3/* 
        - giscus.app/*

  1. MathJax loads web fonts for typesetting of mathematical content through relative URLs, and thus cannot be automatically bundled by the privacy plugin. MathJax can be self-hosted.

    Giscus, which we recommend to use as a comment system, uses a technique called code-splitting to load only the code that is necessary, which is implemented via relative URLs. Giscus can be self-hosted as well.

Excluding specific external assets can be necessary if they contain dynamically created or relative URLs, which can't be resolved by the privacy plugin due to technical limitations.

Why can't Material for MkDocs bundle all assets by design?

The primary reason why Material for MkDocs can't just bundle all of its own assets is the integration with Google Fonts, which offers over a thousand different fonts that can be used to render your documentation. Most of the fonts include several weights and are split up into different character sets to keep the download size small, so the browser only downloads what is really needed. For Roboto, our default regular font, this results in 42 *.woff2 files in total.

If Material for MkDocs would bundle all font files, the download size would be in the hundreds of megabytes, slowing down automated builds. Furthermore, authors might add external assets like third-party scripts or style sheets that would need to be remembered to be defined as further local assets.

This is the very reason the built-in privacy plugin exists — it automates the process of downloading all external assets manually to ensure compliance with GDPR with some some technical limitations.

Sponsors only · insiders-4.26.0 · Experimental

The following configuration options are available for external links:

external_links

Default: true – This option specifies whether the plugin should parse and process external links. If you want to speed up local builds, you can use an environment variable:

plugins:
  - privacy:
      external_links: !ENV [CI, false]
external_links_attr_map

Default: None – This option specifies custom attributes that should be added to external links, like for example target="_blank" so all external links open in a new window:

plugins:
  - privacy:
      external_links_attr_map:
        target: _blank
external_links_noopener

Default: true – This option specifies whether the plugin should automatically add rel="noopener" to all links with target="_blank" for security reasons:

plugins:
  - privacy:
      external_links_noopener: true

How it works

The built-in privacy plugin scans the resulting HTML for links to external resources, including external scripts, style sheets, images and web fonts, and downloads them to bundle them with your documentation site. Every URL referring to an external resource, no matter if part of a template or Markdown file, is then replaced with the URL to the local copy. An example:

<script src="https://example.com/script.js"></script>

The external script is downloaded, and the link is replaced with:

<script src="assets/external/example.com/script.js"></script>

Style sheets are scanned for external url(...) references, e.g. images and web fonts, which are then also downloaded and bundled with your documentation site. This means that Google Fonts can be configured in mkdocs.yml as usual, as the built-in privacy plugin automatically downloads and bundles all dependent resources.

As a third measure, preconnect hints used for DNS pre-fetching which might also leak the visitors IP address to a third party are automatically removed during the build process.

Expand to inspect example

For the official documentation, the built-in privacy plugin downloads the following resources:

.
└─ assets/external/
   ├─ unpkg.com/tablesort@5.3.0/dist/tablesort.min.js
   ├─ fonts.googleapis.com/css
   ├─ fonts.gstatic.com/s/
   │  ├─ roboto/v29/
   │  │  ├─ KFOjCnqEu92Fr1Mu51TjASc-CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TjASc0CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TjASc1CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TjASc2CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TjASc3CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TjASc5CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TjASc6CsQ.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TzBic-CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TzBic0CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TzBic1CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TzBic2CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TzBic3CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TzBic5CsTKlA.woff2
   │  │  ├─ KFOjCnqEu92Fr1Mu51TzBic6CsQ.woff2
   │  │  ├─ KFOkCnqEu92Fr1Mu51xEIzIFKw.woff2
   │  │  ├─ KFOkCnqEu92Fr1Mu51xFIzIFKw.woff2
   │  │  ├─ KFOkCnqEu92Fr1Mu51xGIzIFKw.woff2
   │  │  ├─ KFOkCnqEu92Fr1Mu51xHIzIFKw.woff2
   │  │  ├─ KFOkCnqEu92Fr1Mu51xIIzI.woff2
   │  │  ├─ KFOkCnqEu92Fr1Mu51xLIzIFKw.woff2
   │  │  ├─ KFOkCnqEu92Fr1Mu51xMIzIFKw.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmSU5fABc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmSU5fBBc4.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmSU5fBxc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmSU5fCBc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmSU5fCRc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmSU5fChc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmSU5fCxc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmWUlfABc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmWUlfBBc4.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmWUlfBxc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmWUlfCBc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmWUlfCRc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmWUlfChc4EsA.woff2
   │  │  ├─ KFOlCnqEu92Fr1MmWUlfCxc4EsA.woff2
   │  │  ├─ KFOmCnqEu92Fr1Mu4WxKOzY.woff2
   │  │  ├─ KFOmCnqEu92Fr1Mu4mxK.woff2
   │  │  ├─ KFOmCnqEu92Fr1Mu5mxKOzY.woff2
   │  │  ├─ KFOmCnqEu92Fr1Mu72xKOzY.woff2
   │  │  ├─ KFOmCnqEu92Fr1Mu7GxKOzY.woff2
   │  │  ├─ KFOmCnqEu92Fr1Mu7WxKOzY.woff2
   │  │  └─ KFOmCnqEu92Fr1Mu7mxKOzY.woff2
   │  └─ robotomono/v13/
   │     ├─ L0xTDF4xlVMF-BfR8bXMIhJHg45mwgGEFl0_3vrtSM1J-gEPT5Ese6hmHSV0mf0h.woff2
   │     ├─ L0xTDF4xlVMF-BfR8bXMIhJHg45mwgGEFl0_3vrtSM1J-gEPT5Ese6hmHSZ0mf0h.woff2
   │     ├─ L0xTDF4xlVMF-BfR8bXMIhJHg45mwgGEFl0_3vrtSM1J-gEPT5Ese6hmHSd0mf0h.woff2
   │     ├─ L0xTDF4xlVMF-BfR8bXMIhJHg45mwgGEFl0_3vrtSM1J-gEPT5Ese6hmHSh0mQ.woff2
   │     ├─ L0xTDF4xlVMF-BfR8bXMIhJHg45mwgGEFl0_3vrtSM1J-gEPT5Ese6hmHSt0mf0h.woff2
   │     ├─ L0xTDF4xlVMF-BfR8bXMIhJHg45mwgGEFl0_3vrtSM1J-gEPT5Ese6hmHSx0mf0h.woff2
   │     ├─ L0xdDF4xlVMF-BfR8bXMIjhOsXG-q2oeuFoqFrlnAIe2Imhk1T8rbociImtElOUlYIw.woff2
   │     ├─ L0xdDF4xlVMF-BfR8bXMIjhOsXG-q2oeuFoqFrlnAIe2Imhk1T8rbociImtEleUlYIw.woff2
   │     ├─ L0xdDF4xlVMF-BfR8bXMIjhOsXG-q2oeuFoqFrlnAIe2Imhk1T8rbociImtEluUlYIw.woff2
   │     ├─ L0xdDF4xlVMF-BfR8bXMIjhOsXG-q2oeuFoqFrlnAIe2Imhk1T8rbociImtEm-Ul.woff2
   │     ├─ L0xdDF4xlVMF-BfR8bXMIjhOsXG-q2oeuFoqFrlnAIe2Imhk1T8rbociImtEmOUlYIw.woff2
   │     └─ L0xdDF4xlVMF-BfR8bXMIjhOsXG-q2oeuFoqFrlnAIe2Imhk1T8rbociImtEn-UlYIw.woff2
   └─ polyfill.io/v3/polyfill.min.js

Caching recommended

All downloaded files are written to the .cache directory, significantly reducing the duration of subsequent builds as only replacements need to be carried out. You might want to:

  1. Ignore the .cache directory in your project, by adding it to .gitignore.

  2. When building your site for publishing, use a build cache to save the .cache directory in between builds. Taking the example from the publishing guide, add the following lines:

    name: ci
  on:
    push:
      branches:
        - master
        - main
  jobs:
    deploy:
      runs-on: ubuntu-latest
      steps:
        - uses: actions/checkout@v2
        - uses: actions/setup-python@v2
          with:
            python-version: 3.x
        - uses: actions/cache@v2
          with:
            key: ${{ github.ref }}
            path: .cache
        - run: pip install mkdocs-material
        - run: mkdocs gh-deploy --force

Limitations

Note that dynamically created URLs as part of scripts are not detected, and thus cannot be automatically downloaded. The built-in privacy plugin does not execute scripts – it can only detect fully qualified URLs to download and replace.

In short, don't do this:

const cdn = "https://polyfill.io"
const url = `${cdn}/v3/polyfill.min.js`

Instead, always use fully qualified URLs:

const url ="https://polyfill.io/v3/polyfill.min.js"

Customization

Custom cookies

If you've customized the cookie consent and added a custom cookie, the user will be prompted to accept your custom cookie. Use additional JavaScript to check whether the user accepted it:

var consent = __md_get("__consent")
if (consent && consent.custom) {
  /* The user accepted the cookie */
}

extra_javascript:
  - javascripts/consent.js
Last update: April 14, 2023
Created: April 14, 2023