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This page lists Cloud IoT Core requirements and related information.

Regions and versions

Cloud regions

Only these cloud regions are available: us-central1, europe-west1, and asia-east1.

Transport Layer Security (TLS)

Cloud IoT Core requires TLS version 1.2 or higher. For more guidance on TLS, see the section "Minimum standards for TLS clients" in Disabling SSLv3 and RC4 on the Google Security Blog.

MQTT bridge

MQTT version 3.1.1 is required.

The following features are not supported:

MQTT QoS 2
Arbitrary MQTT topics and subscriptions. For topic requirements, see the section on connecting devices using MQTT
Last Will and Testament (LWT)
Retained messages
Persistent sessions

HTTP bridge

Secure communication (HTTPS) is required.

Cloud IoT Core supports HTTP 1.1 only (not 2.0).

Permitted characters and size requirements

Registries and device identifiers, and their associated fields, are limited to certain characters. These fields are also limited in size (either length or byte size).

The following table lists the permitted characters and sizes for each resource:

Resource	Limitations
Registry IDs	Permitted characters: `[a-zA-Z][-a-zA-Z0-9._+~%]+` First character must be a letter (`[a-zA-Z]`) Cannot start with "goog" Minimum length: 3 characters Maximum length: 255 characters
Device IDs	Must be unique within the parent device registry Permitted characters: `[a-zA-Z][-a-zA-Z0-9._+~%]+` First character must be a letter (`[a-zA-Z]`) Cannot start with "goog" Minimum length: 3 characters Maximum length: 255 characters
Device metadata keys	Permitted characters: `[a-zA-Z][-a-zA-Z0-9._+~%]+` First character must be a letter (`[a-zA-Z]`) Minimum length: 1 character Maximum length: 128 characters Maximum combined total size of all device metadata key-value pairs: 256 KB
Device metadata values	Minimum size: 0 KB Maximum size: 32 KB Maximum combined total size of all device metadata key-value pairs: 256 KB
Subfolders^*	Permitted characters: `[a-zA-Z][-a-zA-Z0-9._+~%]+` First character must be a letter (`[a-zA-Z]`) Maximum size: 256 bytes

"Subfolders" refers to the eventNotificationConfigs.subfolderMatches field in the device registry, which is used when matching MQTT or HTTP subfolders to a Cloud Pub/Sub topic. For more information, see Creating a device registry with multiple Pub/Sub topics.