Why project ID permanence makes format-checking worth doing upfront

GCP project IDs are globally unique across every GCP customer, and once a project ID has been used, it can never be reused by anyone — even after the original project is deleted, that ID stays permanently retired. That permanence is exactly why it's worth validating the format before attempting to create a project rather than finding out interactively: a rejected creation attempt due to a formatting mistake costs a round trip, but it's a cheap one compared to accidentally taking a project ID an automation script or IaC template was specifically written to expect, or discovering a typo'd ID has "burned" a name you wanted to reuse.

ID vs. name vs. number — three different identifiers

GCP deliberately separates three concepts that are easy to conflate: the project ID (this tool's subject) is a permanent, immutable, DNS-safe string used in API calls and resource naming; the project NAME is a mutable, human-friendly display label that can contain spaces and mixed case and can be changed anytime; the project NUMBER is an auto-assigned numeric identifier used internally by some APIs. Scripts and IaC configs should always reference the project ID, not the name — since the name can change without warning, while the ID is guaranteed stable for the project's lifetime.