API Client Variables: Scopes, Precedence, and Secrets Explained

Hardcoding a URL, a token, or an ID directly into a request works until you need to run that same request against a second environment, a second account, or a teammate’s machine. Variables solve this: write {{base_url}} once, and let it resolve to something different depending on where and how the request runs.

The {{variable}} Syntax

Most API clients, HTTP Titan included, use double curly braces: {{base_url}}/users/{{user_id}}. If you ever need a literal {{ in a request body that isn’t meant to be interpolated, escaping it (\{{not_a_variable}}) keeps it as plain text instead of triggering a lookup.

Scopes

Variables typically live at more than one level, from broadest to narrowest:

• Collection variables — shared across every request in a collection, good for values that rarely change (a base URL, a fixed account ID).
• Environment variables — swapped as a set when you switch environments (local / staging / production), so the same collection points somewhere different without editing a single request.
• Local variables — set at runtime, typically from a pre-request script, and scoped to that one request execution.

Precedence

When the same variable name exists at more than one scope, the narrower scope wins: local overrides environment, environment overrides collection. This lets a script temporarily override a value (say, a freshly-fetched token) for one request without touching the environment variable everyone else’s requests still rely on.

Secrets

Not every variable should be visible in plain text — an API key or a password shouldn’t render openly on screen or end up readable in a shared export. A secret variable stores the same way but displays masked in the UI and gets redacted from anywhere it might otherwise be logged, while still resolving correctly when the request actually sends.

Testing Variables in HTTP Titan

HTTP Titan supports all three scopes described above — collection, environment, and local (from pre-request scripts) — with {{name}} interpolation and the same local-over-environment-over-collection precedence. Environment variables can be marked secret, masking the value in the UI while still resolving it correctly at send time — useful for the bearer tokens, API keys, and OAuth credentials a request’s auth usually depends on.