Site assets minifying (or in another word compressing) helps to decrease site load and speed up browser loading time. Just like with CSS and JavaScript, HTML output can be compressed and minified by removing whitespace, new lines, comments and even removing certain optional closing tags, making for smaller file sizes.

Popular static site generator, Hugo version 0.47 introduced the --minify flag command which execute to minify the final HTML output to /public by simply running hugo --minify. Here, we are going to use the same dependency Minify written in Go language by Taco de Wolff. It’s extremely fast compare to other minify tools (and depends upon your site weight).

See also: Deploying Jekyll sites to GitHub Pages using GitHub Actions

Following I have written simple procedures to Minify HTML pages after they have been generated locally with a static website generator like Jekyll.

Building site with Jekyll

First build Jekyll final production site with the following command line:

JEKYLL_ENV=production bundle exec jekyll build --profile --trace

Install Minify

• CLI installation

Deb package on Ubuntu

sudo apt-get update && sudo apt-get -y install minify

Note: may be outdated

Using Homebrew on MacOS

brew install tdewolff/tap/minify

Minify HTML files

• Usage

minify --type=html --recursive --output "./_site/" --match="\.html$" --html-keep-conditional-comments --html-keep-default-attrvals --html-keep-document-tags --html-keep-end-tags --html-keep-quotes "./_site/" --verbose

Minify XML files

You can also minify *.XML files with following command line:

minify --type=xml --recursive --output "./_site/" --match="\.xml$" --xml-keep-whitespace "./_site/" --verbose || true

Minify JSON files

You can also minify *.json files with following command line:

minify --type=json --recursive --output "./_site/" --match="\.json$" "./_site/" --verbose || true

Build, minify and deploy Jekyll site into GitHub Pages using GitHub Actions

If you have hosted your site in GitHub Pages, you can create a workflow for a continuous integration.

GitHub Actions are registered for a repository by using a YAML file inside the directory path .github/workflows (note the dot at the start).

Create a workflow file, say workflow.yml or pages.yml or deploy.yml, using either the GitHub interface or by pushing a YAML file to the workflow directory path manually.

The base contents are:

# Workflow for building and deploying a Jekyll site to GitHub Pages
name: Deploy Jekyll site to Page

on:
  # Runs on pushes targeting the default branch
  push:
    branches: ["main"]

  # Allows you to run this workflow manually from the Actions tab
  workflow_dispatch:

# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
permissions:
  contents: read
  pages: write
  id-token: write

# Allow one concurrent deployment
concurrency:
  group: "pages"
  cancel-in-progress: true

env:
  RUBY_VERSION: "3.1"

jobs:
  # Build job
  build:
    name: build
    runs-on: ubuntu-latest

    steps:
      - name: Checkout
        uses: actions/checkout@v3

      - name: Setup Ruby
        uses: ruby/setup-ruby@v1
        with:
          # Not needed with a .ruby-version file
          ruby-version: ${{ env.RUBY_VERSION }}
          # Runs 'bundle install' and caches installed gems automatically
          bundler-cache: true

      - name: Setup Pages
        id: pages
        uses: actions/configure-pages@v1

      - name: Build with Jekyll
        # Defaults output to '/_site'
        run: bundle exec jekyll build --baseurl ${{ steps.pages.outputs.base_path }} --profile --trace
        env:
          JEKYLL_ENV: production

      # - name: Install Minify deb package on Ubuntu
      #   if: ${{ matrix.os == 'ubuntu-latest' }}
      #   run: apt-get update && apt-get install --no-install-recommends --yes minify

      # https://github.com/tdewolff/homebrew-tap/
      - name: Install Minify using Homebrew
        run: brew install tdewolff/tap/minify

      # https://github.com/tdewolff/minify/tree/master/cmd/minify#usage
      - name: Minify HTML files
        run: |
          minify --type=html --recursive --output "./_site/" --match="\.html$" "./_site/" \
          --html-keep-conditional-comments \
          --html-keep-default-attrvals \
          --html-keep-document-tags \
          --html-keep-end-tags \
          --html-keep-quotes \
          --verbose

      - name: Minify JSON files
        run: |
          minify --type=json --recursive --output "./_site/" --match="\.json$" "./_site/" --verbose || true

      - name: Upload artifact
        # This will automatically upload an artifact from the '/_site' directory
        uses: actions/upload-pages-artifact@v1
        if: ${{ success() && github.ref == 'refs/heads/main' }}
        with:
          path: ./_site/

  # Deployment job
  deploy:
    name: deploy
    environment:
      name: github-pages
      url: ${{ steps.deployment.outputs.page_url }}
    runs-on: ubuntu-latest
    needs: build
    if: ${{ github.ref == 'refs/heads/main' }}
    steps:
      - name: Deploy to GitHub Pages
        id: deployment
        uses: actions/deploy-pages@v1
        if: ${{ success() }}

After so much research and testings I have found, this is the best and fastest method to minify Jekyll’s output HTML files for your site.

If you search on Google you can also find another alternative, Jekyll layout that compresses HTML which is written in pure Liquid. But note that, I do not recommend using it because it slow down your Jekyll build time and has not been updated since long time.