The following table lists the limits associated with the different service tiers S1, S2, S3, and F1. For information about the cost of each unit in each tier, see Azure IoT Hub pricing.
|Resource||S1 Standard||S2 Standard||S3 Standard||F1 Free|
[!NOTE] If you anticipate using more than 200 units with an S1 or S2 tier hub or 10 units with an S3 tier hub, contact Microsoft Support.
The following table lists the limits that apply to IoT Hub resources.
|Maximum paid IoT hubs per Azure subscription||50|
|Maximum free IoT hubs per Azure subscription||1|
|Maximum number of characters in a device ID||128|
|Maximum number of device identities
returned in a single call
|IoT Hub message maximum retention for device-to-cloud messages||7 days|
|Maximum size of device-to-cloud message||256 KB|
|Maximum size of device-to-cloud batch||AMQP and HTTP: 256 KB for the entire batch
MQTT: 256 KB for each message
|Maximum messages in device-to-cloud batch||500|
|Maximum size of cloud-to-device message||64 KB|
|Maximum TTL for cloud-to-device messages||2 days|
|Maximum delivery count for cloud-to-device
|Maximum cloud-to-device queue depth per device||50|
|Maximum delivery count for feedback messages
in response to a cloud-to-device message
|Maximum TTL for feedback messages in
response to a cloud-to-device message
|Maximum size of device twin||8 KB for tags section, and 32 KB for desired and reported properties sections each|
|Maximum length of device twin string key||1 KB|
|Maximum length of device twin string value||4 KB|
|Maximum depth of object in device twin||10|
|Maximum size of direct method payload||128 KB|
|Job history maximum retention||30 days|
|Maximum concurrent jobs||10 (for S3), 5 for (S2), 1 (for S1)|
|Maximum additional endpoints (beyond built-in endpoints)||10 (for S1, S2, and S3)|
|Maximum message routing rules||100 (for S1, S2, and S3)|
|Maximum number of concurrently connected device streams||50 (for S1, S2, S3, and F1 only)|
|Maximum device stream data transfer||300 MB per day (for S1, S2, S3, and F1 only)|
[!NOTE] If you need more than 50 paid IoT hubs in an Azure subscription, contact Microsoft Support.
[!NOTE] Currently, the total number of devices plus modules that can be registered to a single IoT hub is capped at 1,000,000. If you want to increase this limit, contact Microsoft Support.
IoT Hub throttles requests when the following quotas are exceeded.
|Identity registry operations
(create, retrieve, list, update, and delete),
individual or bulk import/export
|83.33/sec/unit (5,000/min/unit) (for S3).
1.67/sec/unit (100/min/unit) (for S1 and S2).
|Device connections||6,000/sec/unit (for S3), 120/sec/unit (for S2), 12/sec/unit (for S1).
Minimum of 100/sec.
|Device-to-cloud sends||6,000/sec/unit (for S3), 120/sec/unit (for S2), 12/sec/unit (for S1).
Minimum of 100/sec.
|Cloud-to-device sends||83.33/sec/unit (5,000/min/unit) (for S3), 1.67/sec/unit (100/min/unit) (for S1 and S2).|
|Cloud-to-device receives||833.33/sec/unit (50,000/min/unit) (for S3), 16.67/sec/unit (1,000/min/unit) (for S1 and S2).|
|File upload operations||83.33 file upload initiations/sec/unit (5,000/min/unit) (for S3), 1.67 file upload initiations/sec/unit (100/min/unit) (for S1 and S2).
10 concurrent file uploads per device.
|Direct methods||24 MB/sec/unit (for S3), 480 KB/sec/unit (for S2), 160 KB/sec/unit (for S1).
Based on 8-KB throttling meter size.
|Device twin reads||500/sec/unit (for S3), Maximum of 100/sec or 10/sec/unit (for S2), 100/sec (for S1)|
|Device twin updates||250/sec/unit (for S3), Maximum of 50/sec or 5/sec/unit (for S2), 50/sec (for S1)|
(create, update, list, and delete)
|83.33/sec/unit (5,000/min/unit) (for S3), 1.67/sec/unit (100/min/unit) (for S2), 1.67/sec/unit (100/min/unit) (for S1).|
|Jobs per-device operation throughput||50/sec/unit (for S3), maximum of 10/sec or 1/sec/unit (for S2), 10/sec (for S1).|
|Device stream initiation rate||5 new streams/sec (for S1, S2, S3, and F1 only).|