ImportError: cannot import name 'BlockBlobService' from 'azure.storage.blob'

TL;DR: BlockBlobService was the v2-track client and v12 deleted it. Either migrate to BlobServiceClient (recommended) or pin azure-storage-blob<3 to keep the old API.

ImportError: cannot import name 'BlockBlobService' from 'azure.storage.blob'

Fix it

1. Decide: migrate or pin. Migrating is better for anything you will maintain.
2. To migrate: pip install -U azure-storage-blob, then replace BlockBlobService(connectionstring=...) usage with BlobServiceClient.fromconnection_string(...), and method calls per the v12 migration guide. Expected: imports succeed.
3. To pin (short-term only): pip install "azure-storage-blob<3". Expected: BlockBlobService imports again.
4. Record the choice in requirements so the next fresh install is deterministic.

When this applies

• The code imports BlockBlobService and pip shows azure-storage-blob 12.x.

When it doesn't

• pip shows 2.x and the import still fails: namespace conflict; see the azure.identity namespace skill.
• You are writing new code: use BlobServiceClient from the start.

Compatibility

• v12: azure-storage-blob >= 12.0. Legacy: azure-storage-blob 2.x.

Why it happens

Major-version SDK rewrites drop old classes. v12 kept the package name but replaced the entire surface, so old imports fail loudly instead of subtly.

Edge cases

• Some third-party libraries still import BlockBlobService internally; pinning may be forced until they migrate.
• Connection strings from the portal work with both tracks, so auth config does not need to change.

Reported in GitHub (gh:wazuh/wazuh#24641): ImportError: cannot import name 'BlockBlobService' from 'azure.storage.blob' (wazuh/wazuh#24641). The verified fix: Asked on Stack Overflow by developers running old Azure samples on new installs. The verified answer: BlockBlobService was removed in v12, so either pin azure-storage-blob to the 2.x track or migrate to BlobServiceClient. Source: the linked Stack Overflow thread. Source: https://github.com/wazuh/wazuh/issues/24641 Thread ref: gh:wazuh/wazuh#24641