> For the complete documentation index, see [llms.txt](https://mercure-technologies.gitbook.io/expo-open-ota/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mercure-technologies.gitbook.io/expo-open-ota/storage/azure-blob-storage.md).

# Azure Blob Storage

Use Azure Blob Storage to store and deliver update assets.

### Configure storage

Set these environment variables:

```dotenv
STORAGE_MODE=azure
AZURE_BLOB_CONTAINER_NAME=your-container-name
AZURE_STORAGE_ACCOUNT_NAME=your-account-name
AZURE_STORAGE_ACCOUNT_KEY=<account access key>
```

The server authenticates with the account access key (shared key). It is required in every case: beyond object operations, the key signs the SAS URLs used for uploads and asset delivery.

`AZURE_BLOB_ENDPOINT` optionally overrides the blob service URL, for example to point at an [Azurite](https://learn.microsoft.com/azure/storage/common/storage-use-azurite) emulator during local development. When unset, the server uses the standard `https://{account}.blob.core.windows.net` endpoint.

### Create the storage account and container

{% stepper %}
{% step %}

#### Create a storage account

In the Azure portal, go to **Storage accounts** and create one. A Standard general-purpose v2 account works fine.
{% endstep %}

{% step %}

#### Create a container

In the storage account, open **Containers** and create a private container for your updates.

Set its name as `AZURE_BLOB_CONTAINER_NAME`. Leave public access disabled: clients never talk to the container directly, every access goes through a SAS URL.
{% endstep %}

{% step %}

#### Retrieve the access key

Open **Security + networking**, then **Access keys**. Show `key1` and set it as `AZURE_STORAGE_ACCOUNT_KEY`, together with the account name in `AZURE_STORAGE_ACCOUNT_NAME`.
{% endstep %}
{% endstepper %}

### Publishing updates

Uploads go directly from the CLI to Azure through short-lived SAS URLs. Azure requires the `x-ms-blob-type` header on those uploads, and the server tells the CLI to send it, so publishing to an Azure-backed server requires an up-to-date `eoas`. Older CLI versions fail at upload time with a `MissingRequiredHeader` error.

### Asset delivery

Azure delivers assets through direct SAS URLs. Each URL expires after 15 minutes, and the container stays private.

{% hint style="success" %}
SAS delivery is enabled automatically in azure mode. No CDN configuration is required.
{% endhint %}

{% hint style="info" %}
Azure has no native CDN able to validate per-URL signatures, so there is no CloudFront-style option on this provider. For edge caching, put a CDN (Azure Front Door or any other) in front of a public container and configure the [Generic CDN](/expo-open-ota/cdn/generic-cdn.md); an explicitly configured `CDN_BASE_URL` takes precedence over SAS delivery.
{% endhint %}


---

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