The Native Rendering Engine
Sub-second document generation. No HTML parsing. No browser overhead. Just pure, structured rendering from JSON to pixel-perfect PDFs and Excel files.
Why Sub-Second Matters
Traditional PDF libraries use HTML-to-PDF conversion. We built a native pipeline that goes directly from template to document.
* Benchmarks based on typical invoice documents with charts and tables. Complex documents may vary.
Four Pillars of the Engine
Every document passes through four specialized systems working in harmony.
Hybrid Logic Engine
Server-side JavaScript for complex calculations. Native Excel formulas for spreadsheet power users. Choose the right tool for each job.
Works in PDF and Excel
14+ Math functions supported
Row-level context in loops
Sandboxed execution (no eval)
Excel-only feature
Live, editable formulas
Works in DataTable columns
Full Excel formula support
TextRuns: Secure by Design
Rich text formatting without HTML parsing. JSON-based runs give you complete control over styling with zero XSS attack surface.
{
"type": "textRuns",
"runs": [
{ "text": "Invoice ", "bold": true },
{ "text": "#12345", "color": "#2563eb" },
{ "text": " is ", "italic": true },
{
"text": "PAID",
"bold": true,
"color": "#16a34a",
"link": "https://..."
}
]
}Invoice #12345 is PAID
Zero XSS attack surface
Consistent across PDF and Excel
Supports links, colors, styles
<!-- User-provided content -->
<p>
<b>Invoice </b>
<span style="color: blue">#12345</span>
<i> is </i>
<script>alert('XSS!')</script>
<b style="color: green">PAID</b>
</p>XSS vulnerability if user content is not sanitized
Requires HTML sanitization
CSS parsing inconsistencies
Cross-platform rendering varies
Yoga-Powered Flexbox
We use Facebook's Yoga layout engine—the same one powering React Native. Get true Flexbox layouts in PDFs without CSS parsing overhead.
Cross-platform consistency
Same layout engine as React Native apps
Familiar syntax
flexDirection, justifyContent, alignItems, gap
Nested containers
Complex layouts with unlimited nesting depth
Percentage & fixed sizing
Mix relative and absolute dimensions
{
"type": "container",
"style": {
"flexDirection": "row",
"justifyContent": "space-between",
"alignItems": "center",
"gap": 16,
"padding": 24
},
"children": [
{
"type": "container",
"style": { "flex": 1 },
"children": [...]
},
{
"type": "container",
"style": { "width": "40%" },
"children": [...]
}
]
}Visual Consistency Layer
Charts are rendered as images and embedded in documents. This ensures your bar chart looks identical whether opened in Excel 2016, Excel 365, or Google Sheets.
Bar
Vertical or horizontal bars
Line
Trend visualization
Pie
Proportional data
Doughnut
Hollow pie charts
Area
Filled line charts
Radar
Multi-axis comparison
Polar Area
Radial segments
Scatter
X-Y data points
Why Image-Based Charts?
100% Identical
Same pixels on every device and viewer
No Compatibility Issues
Works across all Excel versions
PDF and Excel
Same chart rendering for both formats
28 Component Types
From basic text and images to QR codes, barcodes, data tables, and fillable form fields. Everything you need to build production documents.
Upload TTF/OTF files and use them in your templates. Fonts are embedded in the PDF for guaranteed rendering on any device.
Format Capabilities
One template, two output formats. Here's what each supports.
| Feature | PDF | Excel |
|---|---|---|
| Text Formatting (TextRuns) | ||
| Images | ||
| Charts (8 types) | ||
| QR Codes & Barcodes (10 formats) | ||
| Data Tables with Loops | ||
| Calculated Variables (JS) | ||
| Excel Formulas | ||
| Conditional Rendering | ||
| Nested Loops | ||
| Multi-page/Multi-sheet | ||
| Headers & Footers | ||
| Fillable Form Fields (9 types) | ||
| Digital Signatures | ||
| Custom Fonts | ||
| Flexbox Layout (Yoga) |
Ready to Build Faster Documents?
Join thousands of developers using Rynko to generate production-quality PDFs and Excel files in milliseconds.
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