Getting Started with Sirv CDN: A Complete Guide

What Is Sirv CDN?

Most CDNs cache your files and serve them from edge locations. Sirv does that too (24 global PoPs), but it also processes images on the fly. Resize, convert formats, apply effects, adjust quality. All through URL parameters.

Here’s how a request works:

The browser hits the nearest CDN point of presence (PoP)
If the exact variant is cached, it’s returned in about 25ms
If not, the request goes to Sirv’s processing servers (around 55ms for a cached original, around 160ms for first-time processing)
The processed image gets cached at the CDN edge for future requests
Typical accounts see 80-90% cache hit ratios

The practical upshot: upload one master image, serve unlimited variations (different sizes, formats, effects) without pre-generating anything.

Step 1: Create Your Account

500 MB storage and 2 GB monthly CDN transfer
Access to all features including dynamic imaging, 360 spin viewer, and image zoom
3 user accounts
No credit card required

The free plan includes Sirv branding on interactive viewers (spins and zooms). Business plans starting at $19/month remove branding and bump limits to 5-500 GB storage with 20 GB transfer.

For evaluation, Sirv also offers a 30-day trial with 5 GB storage and all Business features unlocked.

Step 2: Upload Your Images

You’ve got several options here, depending on your workflow.

Web Interface (Dashboard)

The simplest approach. Drag and drop files in the Sirv dashboard. You can create folders, organize assets, and preview images directly in the browser.

REST API

Sirv’s REST API supports over 50 methods for file management. To upload programmatically:

# 1. Get an authentication token
curl -X POST https://api.sirv.com/v2/token \
  -H "Content-Type: application/json" \
  -d '{
    "clientId": "YOUR_CLIENT_ID",
    "clientSecret": "YOUR_CLIENT_SECRET"
  }'

# 2. Upload a file
curl -X POST "https://api.sirv.com/v2/files/upload?filename=/images/product.jpg" \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: image/jpeg" \
  --data-binary @product.jpg

Create API credentials in your Sirv account under Settings > API. Tokens expire after 20 minutes by default (configurable up to 7 days).

Rate limits per hour:

Plan	Total Requests	Search	Fetch
Free	500	50	300
Business	7,000	1,000	2,000
Enterprise	14,000	2,000	4,000

S3-Compatible API

Sirv’s storage is S3-compatible, so you can use any AWS SDK or S3 tool you already know:

import boto3

s3 = boto3.client('s3',
    endpoint_url='https://s3.sirv.com',
    aws_access_key_id='YOUR_S3_KEY',
    aws_secret_access_key='YOUR_S3_SECRET'
)

# Upload
s3.upload_file('product.jpg', 'YOUR_BUCKET', 'images/product.jpg')

# List files
response = s3.list_objects_v2(Bucket='YOUR_BUCKET', Prefix='images/')
for obj in response.get('Contents', []):
    print(obj['Key'])

Your S3 bucket name, key, and secret are in Settings > S3. Both AWS Signature v3 and v4 are supported.

This is handy if you already have S3-based workflows or need to integrate with tools like CyberDuck, S3cmd, or Rclone.

FTP

Traditional FTP access is also available. Find your FTP credentials in Settings > FTP. All uploads are secured via SSL.

Remote Fetch

Sirv can pull images from external URLs automatically:

https://YOUR_ACCOUNT.sirv.com/fetch/https://example.com/image.jpg?w=800

This fetches the remote image, caches it on Sirv, and applies any dynamic imaging parameters you add. Useful for migrating from another CDN or processing third-party images.

Step 3: Dynamic Imaging via URL Parameters

This is the fun part. Once an image is on Sirv, append URL parameters to transform it on the fly.

Resizing

# Resize to 800px width (height auto-calculated)
/image.jpg?w=800

# Resize to fit within 800x600 box
/image.jpg?w=800&h=600

# Resize by longest side
/image.jpg?s=1000

# Force fill (crop to exact dimensions)
/image.jpg?w=800&h=600&scale.option=fill

# Generate a square thumbnail
/image.jpg?thumbnail=256

The default scale.option is fit, which maintains aspect ratio. Other options:

fill: crops to fill exact dimensions
ignore: stretches/squishes to fit
noup: prevents upscaling

Format Conversion and Quality

# Force WebP output
/image.jpg?format=webp

# Optimal format (auto-detect best for browser)
/image.jpg?format=optimal

# Adjust JPEG quality (default 80)
/image.jpg?q=85

# PNG optimization
/image.png?png.optimize=true

# Lossy GIF compression
/animation.gif?gif.lossy=20

In practice, you rarely need format=webp because Sirv’s auto-format handles this automatically (more on that in Step 4).

Cropping

# Crop to specific region
/image.jpg?cw=500&ch=300&cx=100&cy=50

# Smart crop: auto-detect point of interest
/image.jpg?w=400&h=400&crop.type=poi

# Face detection crop
/image.jpg?w=400&h=400&crop.type=face

# Trim whitespace
/image.jpg?crop.type=trim

Effects and Adjustments

# Blur
/image.jpg?blur=15

# Sharpen
/image.jpg?sharpen=30

# Grayscale
/image.jpg?grayscale=true

# Sepia tone
/image.jpg?colortone=sepia

# Adjust brightness and contrast
/image.jpg?brightness=20&contrast=10

# Vignette effect
/image.jpg?vignette.value=40

Text and Watermark Overlays

# Add text overlay
/image.jpg?text=SALE&text.color=white&text.size=30&text.position=center

# Add watermark
/image.jpg?watermark=/logos/watermark.png&watermark.position=southeast&watermark.opacity=60

# Tiled watermark
/image.jpg?watermark=/logos/watermark.png&watermark.position=tile

Profiles (Saved Presets)

Instead of repeating long parameter strings, save them as profiles in your Sirv account:

# Apply a saved profile
/image.jpg?profile=product-thumbnail

# Override specific values
/image.jpg?profile=product-thumbnail&w=300

Create profiles in Settings > Profiles. These are especially useful for consistent batch processing across your entire catalog.

Step 4: Auto-Format Detection

Here’s where things get really nice. Sirv automatically detects browser capabilities using the HTTP Accept header and serves the best format:

AVIF for browsers that support it (Chrome 85+, Firefox 93+)
WebP as a fallback (Chrome, Firefox, Edge, Safari 14+)
JPEG/PNG for older browsers

This happens transparently. No <picture> element or format parameters needed. Just reference the original image URL and Sirv handles the rest.

The savings are real:

WebP: roughly 30-60% smaller than equivalent JPEG
AVIF: roughly 40-50% smaller than equivalent JPEG

Quality defaults to 80% for standard displays and 60% for retina (DPR 1.5 or higher), which balances visual quality against file size. You can override these per-image with ?q=85 or globally in your account settings.

Step 5: Responsive Images

Want optimal performance across devices? You’ve got two approaches.

Automatic (Sirv JS)

The easiest way. Sirv’s JavaScript detects each image’s rendered size and requests the right dimensions:

<img class="Sirv" data-src="https://YOUR_ACCOUNT.sirv.com/image.jpg" alt="Product photo">
<script src="https://scripts.sirv.com/sirvjs/v3/sirv.js"></script>

This automatically handles:

Viewport-based sizing: requests images matching the rendered width
Retina detection: serves higher resolution for high-DPI screens
Lazy loading: images load only when approaching the viewport
Auto-format: serves WebP/AVIF based on browser support
Placeholders: optional blur-up or dominant color while loading

Manual (srcset)

For more control, combine Sirv’s URL-based resizing with standard srcset:

<img
  src="https://YOUR_ACCOUNT.sirv.com/image.jpg?w=800"
  srcset="
    https://YOUR_ACCOUNT.sirv.com/image.jpg?w=400 400w,
    https://YOUR_ACCOUNT.sirv.com/image.jpg?w=800 800w,
    https://YOUR_ACCOUNT.sirv.com/image.jpg?w=1200 1200w,
    https://YOUR_ACCOUNT.sirv.com/image.jpg?w=1600 1600w
  "
  sizes="(max-width: 640px) 100vw, (max-width: 1024px) 50vw, 33vw"
  alt="Product photo"
>

The advantage: you maintain one master image on Sirv and the CDN generates each size on demand. No need to upload multiple files.

Step 6: Set Up a Custom Domain

By default, images are served from YOUR_ACCOUNT.sirv.com. For branding and SEO, set up a custom domain like images.yoursite.com:

Go to Settings > Custom Domain in your Sirv account
Add your desired subdomain (e.g., images.yoursite.com)
Create a CNAME record in your DNS pointing to YOUR_ACCOUNT.sirv.com
Sirv automatically provisions an SSL certificate

Custom domains are available on Business and Enterprise plans.

Step 7: Integrate with Your Platform

Sirv has plugins for the major e-commerce and CMS platforms.

WordPress / WooCommerce

Install the Sirv WordPress plugin to automatically serve all media library images through Sirv CDN. The plugin handles URL rewriting, lazy loading, and format optimization.

Shopify

The Sirv Shopify app adds 360 spin viewers, deep image zoom, and CDN delivery to your store.

Magento

The Sirv Magento extension replaces Magento’s media delivery with Sirv’s optimized CDN, adding 360 views and zoom to product pages.

Any Website

For any HTML site, replace image sources with Sirv URLs and add the Sirv JS script:

<!-- Replace static images -->
<img class="Sirv" data-src="https://YOUR_ACCOUNT.sirv.com/product.jpg" alt="Product">

<!-- Add Sirv JS once, before </body> -->
<script src="https://scripts.sirv.com/sirvjs/v3/sirv.js"></script>

Performance Tips

Preconnect for Faster Loading

Add DNS preconnect hints to your HTML <head> to shave 100-300ms off the first image request:

<link rel="preconnect" href="https://YOUR_ACCOUNT.sirv.com" crossorigin>
<link rel="preconnect" href="https://scripts.sirv.com" crossorigin>

Preload Critical Images

For above-the-fold hero images, use <link rel="preload"> to start downloading before the browser parses the page:

<link rel="preload" as="image" href="https://YOUR_ACCOUNT.sirv.com/hero.jpg?w=1200">

Use Profiles for Consistency

Create profiles for common transformations instead of repeating URL parameters:

product-card: 400px wide, 85% quality, face crop
hero-banner: 1600px wide, 90% quality
thumbnail: 150px square, 75% quality

This keeps your markup clean and makes it easy to adjust settings globally.

Monitor Cache Performance

Check your cache hit ratio in the Sirv dashboard under Usage. Aim for 80%+ hits. If your miss rate is high, it usually means:

Too many unique image variations (simplify your URL parameters)
Low-traffic images that expire from cache
Recently uploaded or updated images (first request is always a miss)

What to Explore Next

Once you’re serving images through Sirv CDN, these are worth looking at:

360 Spin Viewer: upload product photos and create interactive spins
Image Zoom: deep zoom with gigapixel support for product detail
3D Model Viewer: embed GLB/glTF models with AR support
Video Streaming: HLS adaptive bitrate for product videos
REST API Docs: full API reference for automation