glu
HTML mode

HTML mode

glu can convert HTML files directly to PDF. Unlike Markdown mode, no default stylesheet is applied — all styling comes from <style> tags, <link> stylesheets, inline styles, or the --css flag.

glu page.html    # → page.pdf

glu detects the mode by the file extension: .html or .htm for HTML mode.

Features

HTML mode supports:

  • Full HTML document structure (<!DOCTYPE html>, <html>, <head>, <body>)
  • <style> tags in <head> (including @page rules)
  • <link rel="stylesheet"> for external CSS files
  • CSS class and element selectors
  • Borders, padding, background colors, border-radius
  • Tables, lists, headings, paragraphs
  • Inline styles

Example 

<!DOCTYPE html>
<html>
<head>
    <style>
        @page { size: a5; margin: 2cm; }
        body { font-family: serif; font-size: 10pt; }
        h1 { color: #336699; font-size: 20pt; }
        .highlight {
            border: 1pt solid #336699;
            padding: 6pt;
            border-radius: 3pt;
        }
    </style>
</head>
<body>
    <h1>Report</h1>
    <p>This PDF was generated from an HTML file.</p>
    <div class="highlight">
        <p>This section has a <strong>blue border</strong>.</p>
    </div>
</body>
</html>

Run with:

glu report.html    # → report.pdf

Conformance level and document metadata

HTML has no frontmatter, so an HTML document declares its PDF conformance level and title inline — in the <head>:

<head>
  <meta name="pdf-format" content="PDF/UA-2">
  <title>Quarterly report</title>
</head>
  • <meta name="pdf-format" content="…"> sets the conformance level (PDF/UA, PDF/UA-2, PDF/A-3b, …) — the HTML equivalent of the Markdown frontmatter format: key. With it, a bare glu report.html produces the tagged PDF directly; no flag needed.
  • <title> becomes the PDF document title (/Title and, for PDF/UA, the XMP dc:title plus /DisplayDocTitle).

The --format command-line flag overrides the meta tag when both are present:

glu --format PDF/UA-2 report.html

Precedence is --format flag › <meta> tag › none.

Mathematics (MathML)

<math> elements are typeset through the OpenType-MATH engine. Point the element at a font carrying an OpenType MATH table and embed the formula inline:

<head>
  <meta name="pdf-format" content="PDF/UA-2">
  <title>MathML demo</title>
  <style>
    @font-face { font-family: "LM Math"; src: url("latinmodern-math.otf"); }
    math { font-family: "LM Math"; font-size: 12pt; }
  </style>
</head>
<body>
  <p>The quadratic formula
  <math>
    <mi>x</mi><mo>=</mo>
    <mfrac>
      <mrow><mo>-</mo><mi>b</mi><mo>&#xb1;</mo>
        <msqrt><msup><mi>b</mi><mn>2</mn></msup><mo>-</mo>
        <mn>4</mn><mi>a</mi><mi>c</mi></msqrt></mrow>
      <mrow><mn>2</mn><mi>a</mi></mrow>
    </mfrac>
  </math>
  solves a quadratic equation.</p>
</body>

Under PDF/UA each formula becomes a tagged Formula element; under PDF/UA-2 the MathML is additionally embedded as an associated file for assistive technology. See Mathematics (MathML) for the supported elements and PDF/UA tagging for the accessibility details.

Companion Lua file

Like Markdown mode, a companion Lua file is loaded automatically if it exists:

page.html     ← your document
page.lua      ← loaded automatically (if present)

The companion file can register callbacks for page backgrounds, overlays, or element processing.

local frontend = require("glu.frontend")

frontend.add_callback("page_init", "bg", function(doc, page, pagenum, pageinfo)
    -- draw page background
end)

Custom CSS via command line

Additional CSS can be loaded with the --css flag:

glu --css extra.css page.html

CSS from the command line is applied after stylesheets from <link> and <style> tags.

Page counters and auxiliary files

HTML mode supports the same page counters, auxiliary file, and _aux table as Markdown mode. Use counter(page) and counter(pages) in @page margin boxes:

<style>
    @page {
        @bottom-center {
            content: counter(page) " / " counter(pages);
            font-size: 9pt;
        }
    }
</style>

See Markdown mode — Page margin boxes and counters for the full documentation.

Leaders (CSS)

Leaders create repeating dot patterns that fill available space — commonly used in table-of-contents entries. Use the CSS content: leader('.') property (from the CSS Generated Content for Paged Media specification) on an empty inline element:

<style>
    .toc-entry { margin-top: 2pt; margin-bottom: 2pt; }
</style>

<p class="toc-entry">
    Chapter 1<span style="content: leader('.')"></span>5
</p>
<p class="toc-entry">
    Chapter 2<span style="content: leader('.')"></span>12
</p>

This produces:

Chapter 1 . . . . . . . . . . . . 5
Chapter 2 . . . . . . . . . . . . 12

The dots are vertically aligned across lines (global grid alignment). The leader pattern can be any string — leader('.') for dots, leader('_') for underscores, etc.

The <span> must be empty (no child content). The content property is parsed from the inline style attribute.

Barcodes

glu can generate barcodes directly as vector graphics in the PDF — no external images needed. Use the <barcode> element in HTML or Markdown:

<barcode type="code128" value="ABC-123" width="4cm" height="1cm"/>

Supported types

Type Attribute value Description
EAN-13 ean13 13-digit product barcode
Code 128 code128 Variable-length alphanumeric barcode
QR Code qr 2D matrix barcode

Attributes

Attribute Required Description
type yes Barcode type (ean13, code128, qr)
value yes The data to encode
width no Width (default: 3cm)
height no Height (default: same as width). For QR codes, height is always equal to width.
eclevel no QR error correction level: L, M (default), Q, or H

Examples

EAN-13 barcode:

<barcode type="ean13" value="4006381333931" width="4cm" height="2cm"/>

QR code with high error correction:

<barcode type="qr" value="https://www.example.com" width="3cm" eclevel="H"/>

In Markdown — since raw HTML is supported, the same element works directly:

# My Product

<barcode type="code128" value="PROD-42" width="5cm" height="1cm"/>

Scan the barcode above for product details.

Differences from Markdown mode

Feature Markdown mode HTML mode
Default stylesheet Built-in (serif, A4, margins) None — you provide all CSS
Frontmatter YAML (title, author, etc.) Not supported
Lua blocks ```{lua} Not supported (use companion .lua)
Inline expressions {= expr =} Not supported
Go templates --template flag Not supported
@page rules Via frontmatter or CSS file Via <style> or <link>

HTML mode is ideal when you need full control over the document structure and styling, or when converting existing HTML content to PDF.

Markdown modeCallbacks