> ## Documentation Index > Fetch the complete documentation index at: https://docs.costgraph.ai/llms.txt > Use this file to discover all available pages before exploring further. # Overview > Tag any resource CostGraph has indexed, without changing your infrastructure Virtual tags let you tag any resource CostGraph has indexed without changing the underlying infrastructure. You describe which resources a tag should cover, and CostGraph applies it live against your cost data. Nothing is written back to your cloud account, so there is nothing to redeploy. ## Why tagging is hard Tagging is one of the most effective ways to express ownership of infrastructure that teams share. A good set of tags turns an anonymous bill into a map of who runs what. The trouble is that ownership is rarely clean. Multiple teams share the same hardware, and in a large organization the number of teams touching a single cluster runs into the hundreds. Some resources belong squarely to one team, many are shared, and a few belong to everyone at once. The mechanics make it harder still. If tags are not enforced from the ground up, you are left with two unappealing options: * **Redeploy** everything with the right tags baked in, coordinating across every team that owns a piece of the infrastructure. * **Tag by hand**, resource by resource, and keep doing it as new resources appear. Neither scales, and both leave gaps that show up later as spend you cannot attribute. ## What a virtual tag is A virtual tag is not a label written back to your cloud account. It is a **rule**, evaluated live against your cost data. You define the conditions that describe a set of resources, and CostGraph applies the tag every time you look at your spend. Because the rule is evaluated live rather than stamped onto a resource, two things follow: * **It is retroactive.** A rule you write today covers the spend you already have, not just spend going forward. * **It keeps up.** The same rule covers the resource a teammate launches tomorrow, with no further work. ## Virtual tags vs. cloud tags Virtual tags do not replace the tags on your cloud resources. They sit alongside them and fill the gaps. | | Cloud tags | Virtual tags | | ----------------------------- | -------------------------------------- | ------------------------------------------- | | Where they live | On the resource, in your cloud account | As a rule in CostGraph | | To change one | Redeploy or edit the resource | Edit the rule | | Applies to past spend | No | Yes | | Covers new resources | Only if re-tagged | Automatically, if the rule matches | | Can reuse existing cloud tags | n/a | Yes, a rule can inherit a cloud tag's value | ## When to use them Reach for virtual tags when you need to attribute cost across shared infrastructure and either cannot enforce tags at deploy time or have gaps in the tags you already have. They are the fastest way to turn unattributed spend into ownership without waiting on the teams that own the infrastructure. ## How it works At a high level, a virtual tag is a **key** with one or more **rules**: * A **key** is the tag name you group spend by, such as `team` or `environment`. * A **rule** describes which resources take a given value, using conditions on fields like service, region, account, or the cloud tags already on the resource. CostGraph evaluates those rules against your cost data at query time, so a tag is available to group and filter by the moment you save it. When several rules could claim the same resource, order decides which one wins, and you can preview exactly what a rule would claim before you save it. The Virtual tags page, listing each tag key with who created it and when ## Next steps Create a tag, write the rules that fill it, preview what they claim, and group your spend by it. Price hardware you own by registering a rate and tagging the resources that bill at it. Related to virtual tags, but for pricing rather than ownership. Generate tag rules from plain English instead of building each one by hand.