Tag overview - resource tagging and classification - Resource Management

Use cases

Search for resources.

You can add tags to resources and search by tag in the Resource Management console or by API. For more information, see Find resources using tags.
Allocate costs.

Plan tags by dimension, such as region, department, environment, or project, then use Cost Analysis and Split Bill to manage costs. For more information, see Use tags for cost allocation.
Automate O&M

Tag resources by environment (production, test), OS (Windows, Linux), or platform (iOS, Android), then create a template in CloudOps Orchestration Service (OOS) to automate O&M. For more information, see Use tags to implement automated O&M.
Control resource access

Use tags with Resource Access Management (RAM) to control the access and operation permissions of RAM users on resources. For more information, see Use tags to control access to resources.

Benefits

Convenience: A unified console for managing tagged resources.
Flexibility: Add, remove, update, or query tags in the console or by API.
Visibility: Manage separate bills by department, product, or project.

Terms

Term	Description
key-value pair	A tag is a key-value pair.
predefined tag	A predefined tag is created in advance and available across all regions. Predefined tags persist even when not attached to resources. Create them during tag planning and attach them during implementation. For more information, see Create a tag.
system tag	System tags are read-only tags that represent standard data relationships. For example, when a cluster is associated with an Elastic Compute Service (ECS) instance, the system adds the cluster ID as a system tag to help determine the instance's attribution. For more information, see View system tags and attached resources.
createdby tag	A createdby tag is a system tag automatically added to resources to identify resource creators, analyze costs and bills, and manage resource costs efficiently. For more information, see Createdby tags.
tag policy	Tag policies define required tags for resources to standardize tagging. Compliant tags improve cost allocation, access control, and automated O&M efficiency. Two modes are supported: single-account and resource directory. For more information, see Overview of tag policies.

Supported services

Core Alibaba Cloud services support tags, including ECS, ApsaraDB RDS, Object Storage Service (OSS), Virtual Private Cloud (VPC), Server Load Balancer (SLB), and Container Service for Kubernetes (ACK). More services are being added. For more information, see Cloud services that support tags.

Limits

Item	Limit	Adjustable	Remarks
Tags per resource	20	Apply for a quota	The quota varies by resource type. Check adjustability in Quota Center. Approved quota increases take effect within one hour. When increasing the quota for ECS instances, also increase quotas for ECS disks and ECS elastic network interfaces (ENIs), which are created together with instances.
Predefined tags per account	1,000	N/A	N/A
Values per predefined tag key	1,000	N/A	N/A
Tag key	Up to 128 characters. Allows letters, digits, spaces, and these special characters: `_ . # / = + - @`. Cannot start with `aliyun` or `acs:`, or contain `http://` or `https://`. Note Tag key constraints may vary by cloud service. Check the specific service documentation.	N/A	N/A
Tag value	Up to 128 characters. Allows letters, digits, spaces, and these special characters: `_ . # / = + - @`. Cannot start with `aliyun` or `acs:`, or contain `http://` or `https://`. Note Tag value constraints may vary by cloud service. Check the specific service documentation.	N/A	N/A
Adding tags to resources	Each tag key on a resource can have only one value. Adding a tag with the same key as an existing tag overwrites the existing value. For example, if a resource has the `city:shanghai` tag and you add `city:newyork`, the `city:shanghai` tag is replaced.	N/A	N/A

Billing

You can use this service without activating it.

This service is free of charge. However, if the Alibaba Cloud services that work with it are not free of charge, you are charged for the services based on their billing methods.