The Data Cascade

In Eleventy, data is merged from multiple different sources before the template is rendered. The data is merged in what Eleventy calls the Data Cascade.

Sources of Data Jump to heading #

When the data is merged in the Eleventy Data Cascade, the order of priority for sources of data is (from highest priority to lowest):

1. Computed Data
2. Front Matter Data in a Template
3. Template Data Files
4. Directory Data Files (and ascending Parent Directories)
5. Front Matter Data in Layouts (this moved in 1.0)
6. Configuration API Global Data
7. Global Data Files

Example Jump to heading #

---
title: This is a Good Blog Post
tags:
  - CSS
  - HTML
layout: my-layout.njk
---

---
title: This is a Very Good Blog Post
author: Zach
tags:
  - JavaScript
---

Note that when my-template.md and my-layout.njk share data with the same object key (title and tags), the “leaf template” my-template.md takes precedence.

The data cascade results in the following data when my-template.md is rendered:

{
  "title": "This is a Good Blog Post",
  "author": "Zach",
  "tags": [
    "CSS",
    "HTML",
    "JavaScript"
  ],
  "layout": "my-layout.njk"
}

By default in v1.0, Eleventy does a deep data merge to combine Object literals and Arrays. If you want to opt-out of this behavior and revert to a simple top level merge (Object.assign) from the different data sources, you can turn off Data Deep Merge. You can override this on a per-property basis too—read more at the Data Deep Merge documentation.

From the Community Jump to heading #

I Finally Understand Eleventy’s Data Cascade

+ Add yours!

×24 resources courtesy of 11tybundle.dev curated by Bob Monsour

• Programmatically importing your Last.fm listening data to ListenBrainz — Cory Dransfeldt (2023)
• Popular Pages with Eleventy and Fathom Analytics — Robb Knight (2023)
• Scratch that...use the Google Sheets API — Bob Monsour (2023)
• Build a Blogroll with Eleventy — Ben Myers (2023)
• Taking Eleventy into the Spiderverse with eleventy-fetch — Jeff Sikes (2023)

Other pages in Using Data:

• Configure your Templates
• Eleventy Supplied Data
• Data Cascade
  • Front Matter Data
    • Custom Front Matter
  • Template & Directory Data Files
  • Global Data Files
    • Data Preprocessing
  • Data Deep Merge
  • Config Global Data
  • Computed Data
• Environment Variables
• JavaScript Data Files
• Custom Data File Formats