Flags and configuration

Flags and configs are the two things Featly resolves. They share one evaluation engine and one targeting model; the difference is intent.

Feature flags

A flag is a named decision your code asks Featly to make.

• Boolean flags answer yes/no: await featly.Flags.IsEnabledAsync("new-checkout").
• Multivariate flags return one of several typed variants. A variant has a key, a name, and a typed value (Boolean, String, Int, Double, or Json).

Every flag declares a default variant that is served when the flag is disabled or no rule matches. A flag also has an enabled switch — when off, the default variant always wins, regardless of rules.

bool useV2 = await featly.Flags.IsEnabledAsync("new-checkout", ctx);

// Multivariate, typed:
string theme = await featly.Flags.GetStringValueAsync("checkout-theme", "classic", ctx);

Evaluation returns an EvaluationResult<T> carrying the value, the winning variant key, and a reason (Static, TargetingMatch, Split, Default, Disabled, NotFound, Error) — never an exception for control flow.

Dynamic configuration

A config is a typed value resolved through the same targeting engine, for things that should change without a deploy: timeouts, limits, copy, tuning parameters.

int timeout = await featly.Configs.GetAsync<int>("checkout.timeout", 30, ctx);

Config values can be String, Int, Decimal, Bool, or Json. A Json config is the escape hatch for structured settings — a whole object you can target per environment or audience.

Because configs run through the same rules engine, everything you can do with flag targeting (rules, segments, weighted splits) applies to configs too.

Flags vs configs — which to use

Use a flag when…	Use a config when…
The decision is on/off or one-of-N behaviour	You need a value (number, string, object)
You’ll remove it after rollout	It’s a long-lived tunable
You ask “is this on for this user?”	You ask “what value applies to this context?”

The value type

Both flags and configs store their payload as a JsonElement internally, so a single model covers every value kind. The SDK’s typed accessors (GetAsync<int>, GetStringValueAsync, …) convert on read; a type mismatch surfaces as an Error reason and the default value, not an exception.

Next

• Targeting and rules — how a context picks a variant.
• Dashboard tour — create and edit flags and configs in the UI.