Digital Stacks Quick Reference Guide

What is Digital Stacks?

The Digital Stacks is Stanford's web service for accessing files stored in the Stanford Digital Repository (SDR). It provides direct HTTP access to preserved digital content.

Related Stanford resources:

URL Patterns

Basic File Access

https://stacks.stanford.edu/file/druid:[DRUID]/[filename]

Example:

https://stacks.stanford.edu/file/druid:vb564st1676/graduation-stanford.tif

Components

  • Base URL: https://stacks.stanford.edu
  • Path: /file/ (indicates file access, not PURL landing page)
  • DRUID: druid:vb564st1676 (unique identifier, always prefixed with "druid:")
  • Filename: graduation-stanford.tif (the specific file within the object)

DRUIDs Explained

DRUID = Digital Repository Unique Identifier

Format

  • Always 11 characters after "druid:"
  • Pattern: 2 letters + 3 numbers + 2 letters + 4 numbers
  • Example: vb564st1676 breaks down as vb + 564 + st + 1676

Characteristics

  • Permanent: Never changes, even if metadata is updated
  • Unique: No two objects share the same DRUID
  • Case-sensitive: Vb564st1676 ≠ vb564st1676
  • Guaranteed: Works forever (permanent URLs)

Where to Find DRUIDs

  1. PURL URL: Look at the end of https://purl.stanford.edu/vb564st1676
  2. SearchWorks: In the URL or metadata
  3. SDR Deposit Receipt: Provided when you deposit

PURL vs. Digital Stacks

PURL (Persistent URL)

https://purl.stanford.edu/vb564st1676

Purpose: Human-readable landing page

Shows:

  • Title and description
  • Preview images
  • Metadata
  • Download links
  • Citation information

Use when: Sharing with readers, citing in papers, general reference

Digital Stacks File URL

https://stacks.stanford.edu/file/druid:vb564st1676/data.geojson

Purpose: Direct file access

Provides:

  • Raw file content
  • Machine-readable
  • Can be loaded directly by applications
  • No HTML wrapper

Use when: Embedding in code, API access, direct loading

Common Use Cases

1. Display an Image

<img src="https://stacks.stanford.edu/file/druid:abc123xyz456/photo.jpg" alt="Description">

2. Load GeoJSON Data

fetch('https://stacks.stanford.edu/file/druid:abc123xyz456/boundaries.geojson')
  .then(response => response.json())
  .then(data => {
    L.geoJSON(data).addTo(map);
  });

<a href="https://stacks.stanford.edu/file/druid:abc123xyz456/report.pdf">Download Report</a>

4. Embed a Cloud Optimized GeoTIFF

const cogUrl = "https://stacks.stanford.edu/file/druid:vb564st1676/aerial_imagery.tif";
parseGeoraster(cogUrl).then(georaster => {
  const layer = new GeoRasterLayer({
    georaster: georaster
  }).addTo(map);
});

5. Use Tile Directory

L.tileLayer('https://stacks.stanford.edu/file/druid:abc123xyz456/tiles/{z}/{x}/{y}.png', {
  maxZoom: 18
}).addTo(map);

Relative Paths in SDR Deposits

When you deposit files to SDR with a folder structure, that structure is preserved:

Your Deposit Structure

my-collection/
├── index.html
├── styles.css
├── data/
│   ├── points.geojson
│   └── boundaries.geojson
└── images/
    └── logo.png

After Deposit (DRUID: abc123xyz456)

Files are accessible at:

  • https://stacks.stanford.edu/file/druid:abc123xyz456/index.html
  • https://stacks.stanford.edu/file/druid:abc123xyz456/styles.css
  • https://stacks.stanford.edu/file/druid:abc123xyz456/data/points.geojson
  • https://stacks.stanford.edu/file/druid:abc123xyz456/images/logo.png

Using Relative Paths

In your index.html:

<link rel="stylesheet" href="styles.css">
<img src="images/logo.png">
<script>
  fetch('data/points.geojson')
    .then(response => response.json())
    .then(data => console.log(data));
</script>

These relative paths work both:

  • Locally on your computer during development
  • After deposit to SDR via Digital Stacks

No code changes needed!

File Types Supported

Digital Stacks serves any file type:

Common Formats

  • Images: JPG, PNG, GIF, TIFF (including GeoTIFF)
  • Documents: PDF, TXT, HTML, XML
  • Data: CSV, JSON, GeoJSON, XML
  • Geospatial: SHP (shapefiles), KML, GeoTIFF, COG
  • Multimedia: MP3, MP4, WAV (check format restrictions)
  • Archives: ZIP (served as-is, not extracted)

Special Formats

  • Cloud Optimized GeoTIFF (COG): Streams efficiently, perfect for web maps
  • PMTiles: Vector tile format for efficient map delivery
  • Tiles: Directory structures with {z}/{x}/{y} patterns work great

CORS (Cross-Origin Resource Sharing)

Digital Stacks enables CORS, meaning you can:

  • Load files from Digital Stacks in JavaScript from any domain
  • Use fetch(), XMLHttpRequest, or other AJAX methods
  • Embed in web maps hosted anywhere
  • Build applications on different servers that reference Digital Stacks

No CORS errors! Unlike many file servers, Digital Stacks is designed for web application use.

Best Practices

1. Use Relative Paths in Your Deposit

Good:

<img src="images/photo.jpg">
<script src="scripts/map.js"></script>

Avoid:

<img src="https://stacks.stanford.edu/file/druid:abc123/images/photo.jpg">

Why? Relative paths work during development AND after deposit automatically.

2. Keep Folder Structure Simple

Good structure:

index.html
css/styles.css
js/app.js
data/file.geojson
images/photo.jpg

Why? Easy to navigate, intuitive paths, works well in Digital Stacks

3. Name Files Clearly

Good:

stanford_campus_boundary.geojson
aerial_photo_2024.tif
collection_metadata.json

Avoid:

data1.json
img.tif
file.geojson

Why? Clear names make files self-documenting and easier to reference

4. Include a README

In your deposit root:

README.md or README.txt

Include:

  • Description of contents
  • File format information
  • How to use the files
  • Data sources and credits
  • License information

5. Test Locally First

Before depositing:

  1. Test all file paths work on your local machine
  2. Use relative paths throughout
  3. Verify links and references
  4. Check in multiple browsers

After deposit:

  1. Test all links via Digital Stacks URLs
  2. Verify functionality is preserved
  3. Check on different devices

Troubleshooting

File Not Found (404 Error)

Check:

  • DRUID is correct (case-sensitive)
  • Filename matches exactly (including extension)
  • File actually exists in your deposit
  • Path structure is correct

CORS Errors

Should NOT happen with Digital Stacks, but if you see them:

  • Make sure you're using https://stacks.stanford.edu (not http)
  • Check that the DRUID is correct
  • Verify the file is publicly accessible

Slow Loading

For large files:

  • Use Cloud Optimized formats (COG for rasters)
  • Generate tiles for very large datasets
  • Consider file size optimization
  • Check your internet connection

Relative Paths Don't Work After Deposit

Double check:

  • Paths use forward slashes / (not backslashes \)
  • Paths are relative to the current file (use ./ or ../ appropriately)
  • No absolute paths sneaked in (starting with / or http://)

Examples from This Workshop

Stanford Campus COG

https://stacks.stanford.edu/file/druid:vb564st1676/graduation-stanford_stanford-california_20240616_171600_ssc2_nrg_flat_50cm_rotated-154_large_COG.tif

DRUID: vb564st1676

File: graduation-stanford_..._COG.tif

Type: Cloud Optimized GeoTIFF (aerial imagery)

Use: Display high-resolution aerial photography in web maps

World PMTiles

https://stacks.stanford.edu/file/druid:hf224mw4004/20231116.pmtiles

DRUID: hf224mw4004

File: 20231116.pmtiles

Type: PMTiles (vector tiles)

Use: Global base map alternative to raster tiles

Getting Your Own DRUID

To deposit content and get a DRUID:

  1. Contact Stanford Libraries about SDR deposits
  2. Prepare your content with proper folder structure
  3. Submit via deposit system (varies by collection)
  4. Receive DRUID in deposit confirmation
  5. Access via Digital Stacks immediately

Questions? Contact Stanford Libraries digital repository team

Additional Resources

Remember: Digital Stacks + relative paths = web applications that work forever! 🎉

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