Ironpress

Pure rust HTML/CSS/Markdown to PDF converter. No browser, no system dependencies.

Try it in your browser | HTML parity report | Wiki

Performance

Criterion measures complete, in-process conversion to PDF bytes:

Document	Representative median	Approx. conversions/sec
Simple HTML (<h1> + <p>)	0.93 ms	1,080
Styled HTML (CSS, lists, links)	3.5 ms	285
Table (5 rows, styled headers)	5.9 ms	170
Markdown (headings, code, lists)	7.0 ms	143
Full report (tables, flex, progress bars)	15.9 ms	63
Full report + header/footer	15.9 ms	63
200 CJK text-emphasis spans	310 ms	3.2

Measured on macOS ARM (Apple M2) with Rust 1.94.0 at commit 600aadb. The benchmark profile uses opt-level=3, fat LTO, and one codegen unit. Results depend on hardware and document content; conversions/sec is not a page-throughput claim. Reproduce the measurements with:

cargo bench --bench conversion

Quick start

use ironpress::html_to_pdf;

let pdf = html_to_pdf("<h1>Hello</h1><p>World</p>").unwrap();
std::fs::write("output.pdf", pdf).unwrap();

let pdf = ironpress::markdown_to_pdf("# Hello\n\nWorld").unwrap();

CLI

cargo install ironpress

ironpress input.html output.pdf
ironpress document.md output.pdf
ironpress --page-size letter --landscape --margin 54 input.html output.pdf
ironpress --header "Report" --footer "Page {page} of {pages}" input.html output.pdf
echo '<h1>Hello</h1>' | ironpress --stdin output.pdf

Builder API

use ironpress::{HtmlConverter, Margin, PageSize, RasterQuality};

let pdf = HtmlConverter::new()
    .page_size(PageSize::LETTER)
    .margin(Margin::uniform(54.0))
    .raster_quality(RasterQuality {
        background_dpi: 144.0,
        ..RasterQuality::default()
    })
    .header("My Document")
    .footer("Page {page} of {pages}")
    .convert("<h1>Custom page</h1>")
    .unwrap();

RasterQuality keeps source-image, filter, and flattened-background resolution in one physical-DPI policy. Its default preserves sharp source/filter output while using 192 DPI for flattened synthetic backgrounds; lowering one field does not change page geometry. The CLI exposes the same controls through --image-dpi, --filter-dpi, and --background-raster-dpi.

Features at a glance

Area	Highlights	Details
HTML	50+ elements: headings, tables, lists, forms, media, <img>, inline <svg>	Layout Engine
CSS	Flexbox, grid, multi-column, calc(), variables, @media, @page, @font-face	CSS Support
Fonts	Base-14 PDF fonts, custom TTF embedding with subsetting, system font discovery, Unicode/CJK fallback	Font System
Math	LaTeX via $...$ / $$...$$: fractions, roots, matrices, Greek, operators	Math Engine
SVG	Vector rendering: path, shapes, gradients, transforms, clip paths, viewBox	Layout Engine
Images	JPEG + PNG, data URIs, local files, remote URLs (remote feature)	Architecture
PDF	PDF 1.4, bookmarks, link annotations, headers/footers, gradients, streaming output	PDF Rendering
WASM	npm install ironpress - runs 100% client-side in the browser	WASM & Playground
Testing	3500+ unit tests, property-based tests, 6 fuzz targets, 1,662-fixture parity corpus	Testing Strategy

Custom fonts

let pdf = HtmlConverter::new()
    .add_font("Inter", std::fs::read("Inter.ttf").unwrap())
    .convert(r#"<p style="font-family: Inter">Shaped with HarfBuzz</p>"#)
    .unwrap();

Fonts are shaped with rustybuzz, subset to used glyphs only, and embedded as CIDFontType2. Characters outside WinAnsi (CJK, Arabic, emoji) are rendered via automatic Unicode font fallback. See Font System.

Math

The equation $E = mc^2$ is famous.

$$\sum_{k=1}^{n} k = \frac{n(n+1)}{2}$$

Full LaTeX support: fractions, roots, matrices, Greek letters, operators, delimiters, accents. See Math Engine.

Python / Ruby

pip install ironpress

import ironpress
pdf = ironpress.html_to_pdf("<h1>Hello</h1>")

gem install ironpress

require "ironpress"
pdf = Ironpress.html_to_pdf("<h1>Hello</h1>")

WASM

npm install ironpress

import init, { htmlToPdf, markdownToPdf } from 'ironpress';
await init();

const pdf = htmlToPdf('<h1>Hello</h1>');
const blob = new Blob([pdf], { type: 'application/pdf' });

See WASM & Playground.

Security

HTML is sanitized by default: <script>, <iframe>, event handlers, and javascript: URLs are stripped. Resources are sandboxed (local-only by default, 10 MB cap). SVG sanitizer strips dangerous elements. PNG decompression capped at 50 MB. Disable with .sanitize(false) if you trust the input.

How it works

HTML/Markdown → Sanitize → Parse (html5ever) → Style cascade → Layout engine → PDF 1.4

See Architecture for the full pipeline.

Visual parity harness

tests/parity/ is an adversarial HTML/CSS corpus with one focused fixture per feature, value, or interaction. Ironpress produces the candidate PDF; the declared oracle renderer's PDF is committed. At test time both PDFs go through the same discovered pdftoppm executable with the same 300 DPI arguments. A fixture passes only when a fixed, same-coordinate human-visibility policy finds no visible defect. Every raw RGBA difference remains in the evidence; the harness never translates, registers, or fixture-tunes either raster.

scripts/parity.sh                       # run the complete exact parity gate
scripts/parity-gen-refs.sh <category>   # regenerate oracle PDFs explicitly
scripts/parity-gen-refs.sh --check      # authenticate the complete corpus

• Run it: scripts/parity.sh supplies a fresh invocation identity, renders every fixture in-process, rasterizes candidate and oracle PDFs symmetrically, and verifies that JSON, Markdown, and HTML all belong to that invocation.
• Read it: the HTML parity report provides the complete visual evidence; tests/parity/REPORT.md is the compact, problem-first summary, and tests/parity/report.json contains the complete machine result.
• Oracles: committed PDFs are the source of truth. Oracle-preview, candidate, and diff PNGs are generated report evidence and are intentionally ignored. refs.lock authenticates each fixture, oracle PDF, manifest entry, renderer, fonts, and generator provenance. Every future oracle PDF is generated only by the pinned Chromium Fontations/Foundation launcher; authenticated historical non-Chromium PDFs are evidence-only and cannot be regenerated.
• Baseline: tests/parity/baseline.json is a separately reviewed regression snapshot. Updating it is explicit; retained FAILs remain current-health failures while their exact rasters become protected against movement or worsening.
• CI: .github/workflows/parity.yml runs the same browser-free gate, checks refs.lock, and uploads the current report and evidence even when defects make the gate fail.

License

MIT