Azure Blob Storage

What is Blob Storage?

Azure Blob Storage is an object storage service — it stores files as objects (blobs) in containers. Unlike a file system (which organises files in folders), Blob Storage is flat — there are no real folders, just containers with blobs inside. You can simulate folder structure using "/" in blob names (e.g., images/2026/photo.jpg), but these are just naming conventions.

The Three Blob Types

Azure Blob Storage supports three types of blobs — each optimised for different use cases:

Block Blobs

The most common type. Used for storing text and binary data — documents, images, videos, backups. Block blobs are made up of blocks of data that can be managed individually. Maximum size: 190.7 TB.

Append Blobs

Optimised for append operations — adding data to the end of the blob. Perfect for logging, where you continuously write new log entries. You cannot modify existing content — only append. Maximum size: 195 GB.

Page Blobs

Optimised for random read/write operations. Historically used for Azure VM disks (VHD files). Maximum size: 8 TB. For new workloads, use Managed Disks instead of page blobs.

Containers

Blobs are organised into containers — similar to folders or buckets. Every blob must be in a container. A storage account can have unlimited containers.

# Create a container
az storage container create \
  --name images \
  --account-name mystorageaccount2026 \
  --auth-mode login

# List containers
az storage container list \
  --account-name mystorageaccount2026 \
  --output table \
  --auth-mode login

Container Naming Rules

• 3–63 characters
• Lowercase letters, numbers, and hyphens only
• Must start with a letter or number
• Cannot have consecutive hyphens

Container Access Levels

Every container has an access level that controls who can read blobs without authentication:

Blob URLs

Every blob has a unique URL. The format is:

https://[storageaccount].blob.core.windows.net/[container]/[blobname]

# Example:
https://mystorageaccount2026.blob.core.windows.net/images/logo.png
https://mystorageaccount2026.blob.core.windows.net/backups/db-backup-2026-05-07.bak

If the container is public (Blob access level), anyone can access the blob via this URL directly in a browser. If private, you need authentication credentials or a SAS token.

Uploading and Downloading Blobs

# Upload a file
az storage blob upload \
  --account-name mystorageaccount2026 \
  --container-name images \
  --name logo.png \
  --file ./logo.png \
  --auth-mode login

# Upload entire folder
az storage blob upload-batch \
  --account-name mystorageaccount2026 \
  --destination images \
  --source ./my-images/ \
  --auth-mode login

# Download a blob
az storage blob download \
  --account-name mystorageaccount2026 \
  --container-name images \
  --name logo.png \
  --file ./downloaded-logo.png \
  --auth-mode login

# List blobs in a container
az storage blob list \
  --account-name mystorageaccount2026 \
  --container-name images \
  --output table \
  --auth-mode login

# Delete a blob
az storage blob delete \
  --account-name mystorageaccount2026 \
  --container-name images \
  --name logo.png \
  --auth-mode login

Static Website Hosting

Blob Storage can host static websites directly — HTML, CSS, JavaScript, images — with no server required. Perfect for React, Vue, or any static site.

# Enable static website
az storage blob service-properties update \
  --account-name mystorageaccount2026 \
  --static-website \
  --index-document index.html \
  --404-document 404.html \
  --auth-mode login

# Upload your website files
az storage blob upload-batch \
  --account-name mystorageaccount2026 \
  --destination '$web' \
  --source ./dist/ \
  --auth-mode login

Your site is then accessible at: https://[accountname].z13.web.core.windows.net

Soft Delete and Versioning

Two features that protect against accidental deletion or modification:

Blob Soft Delete

When enabled, deleted blobs are retained for a configurable retention period (1–365 days) before being permanently removed. You can restore accidentally deleted blobs within this window.

Blob Versioning

Automatically saves previous versions of a blob every time it's modified. You can restore any previous version. Ideal for important documents that are updated frequently.

Real-World Use Cases