# Tags and tag coverage

Tags are the key-value labels your teams put on cloud resources. Costfluent reads them with every collection; it never writes them. Open **Settings**, then **Tags**.

## Before you start

- Tag keys appear once a sync brings in tagged resources. Nothing creates a key in Costfluent: a key exists because a resource carries it.
- Deleting a tag key and setting a coverage alert need the Owner or Editor team role in a workspace your team can edit.

## Read tag coverage

The **Tag Coverage** card shows, for the last 30 days:

- **Overall Coverage**: the share of cost on tagged resources;
- **Tagged Spend** and **Untagged Spend**;
- **Top Tag Keys**: the five keys carrying the most cost.

The same card appears on the **Insights** page.

## Get an alert when coverage drops

1. On the **Tag Coverage** card, select **Set Alert**.
2. Enter an **Alert Name** and a **Coverage Threshold** in percent.
3. Create the alert.

Costfluent checks coverage every hour and raises the alert when it falls below the threshold. The alert appears in **Alerts** as Low tag coverage and as an in-product notification. See [Alerts](/planning/alerts).

## Review tag keys

**Tag keys** lists each key found in your cost data with its number of values and when it was last seen. Delete a key to make Costfluent forget it; it reappears on the next sync if your resources still carry it.

## Use tags in reports and rules

- Filter or group a cost report by Tag and choose the **Tag key**; see [Explore cost data](/cost-reports/explore).
- Match an allocation rule on a tag; see [Segments and allocation rules](/allocation/segments).
- When the same meaning is spread over several keys, or some resources are untagged, a [virtual tag](/allocation/virtual-tags) gives every cost line one value.

## Related

- [Allocation model](/concepts/allocation-model)
- [Virtual tags](/allocation/virtual-tags)