confkit vs the alternatives

How confkit compares to popular Go configuration libraries — envconfig, Viper, and koanf.

⚡

confkit vs Viper

Typed generics vs stringly-typed access. Validation, secret redaction, 2 deps vs 30+.

🌍

confkit vs envconfig

Multi-source loading vs env-only. Defaults and validation tags vs manual boilerplate.

🔌

confkit vs koanf

Batteries-included vs modular provider system. Built-in validation, defaults, redaction.

Feature Comparison

At a glance — which library gives you what.

Feature	confkit	envconfig	Viper	koanf
Typed struct loading	✅	✅	⚠️	⚠️
Environment variables	✅	✅	✅	✅
YAML / JSON / TOML files	✅	❌	✅	✅
CLI flags	✅	❌	✅	✅
Defaults via struct tags	✅	❌	❌	❌
Built-in validation rules	✅	❌	❌	❌
Secret redaction	✅	❌	❌	❌
Cloud sources (Vault, AWS…)	optional	❌	partial	plugins
Human-readable error context	✅	⚠️	⚠️	⚠️
Multi-source merging	✅	❌	✅	✅
Hot reload	✅	❌	✅	❌
String interpolation	✅	❌	❌	❌
Schema / help generation	✅	❌	❌	❌
Cross-field validation	✅	❌	❌	❌
Generics API	✅	❌	❌	❌
Stdlib only (no deps)	core only	✅	❌	❌

confkit vs envconfig

Use confkit if you want struct-first, type-safe config loading with validation, defaults, and secret redaction — from multiple sources.

Use envconfig if you only care about environment variables and want the smallest possible library.

Scope

confkit

cfg, err := confkit.Load[Config](
    confkit.FromYAML("config.yaml"),
    confkit.FromEnv(),
    confkit.FromFlags(),
)

Multiple sources. Precedence is explicit. Merge is automatic.

envconfig

var cfg Config
envconfig.Process("APP", &cfg)
// Only reads from os.Getenv()

Environment variables only. No files, no flags.

Defaults

confkit

type Config struct {
    Port int `env:"PORT" default:"8080"`
}

envconfig

// No default tag support.
// Must post-process:
if cfg.Port == 0 {
    cfg.Port = 8080
}

Validation

confkit

type Config struct {
    Port int `env:"PORT" validate:"min=1,max=65535"`
}
// Validates automatically on Load()

envconfig

// No validation — write it yourself:
if cfg.Port < 1 || cfg.Port > 65535 {
    log.Fatal("port out of range")
}

Error Messages

confkit — human-readable

Invalid configuration:

  Port
    error: must be between 1 and 65535
    got: 99999
    source: env (PORT)

envconfig — raw Go errors

envconfig: required key PORT missing value
// No source, no context, no value

Secret Redaction

confkit

type Config struct {
    APIKey string `env:"API_KEY" secret:"true"`
}
// Error: API_KEY=*** (auto-redacted)

envconfig

// No redaction.
// Passwords appear in error messages:
// envconfig: API_KEY=s3cr3t invalid

confkit vs Viper

Viper is a popular, flexible config library — but it's stringly-typed, has no built-in validation, and complex error recovery.

confkit is typed from the start. Every value comes out of Load[T] as the correct Go type, validated and ready to use.

confkit — typed

cfg, err := confkit.Load[Config](
    confkit.FromYAML("config.yaml"),
    confkit.FromEnv(),
)
// cfg.Port is an int. Always.
// Validated. Defaults applied.

Viper — stringly-typed

viper.SetConfigFile("config.yaml")
viper.AutomaticEnv()
viper.ReadInConfig()

port := viper.GetInt("port")
// Returns 0 if missing. No error.
// No validation. No defaults via tags.

	confkit	Viper
Type safety	Generics — compile-time	Runtime casting with GetInt/GetString
Validation	Built-in via struct tags	None — write manually
Error reporting	Structured, human-readable	Silent failures (returns zero values)
Secret redaction	Automatic via secret tag	Not supported
Defaults	default struct tag	viper.SetDefault() — imperative
Hot reload	LoadWithWatcher	WatchConfig + OnConfigChange

confkit vs koanf

koanf is modular and extensible, but low-level — you write the integration glue. confkit is opinionated and complete out of the box.

	confkit	koanf
API style	Generic Load[T] → typed struct	koanf.Unmarshal into struct
Validation	Built-in	None — integrate go-validator manually
Defaults	default struct tag	None — write code
Secret redaction	Automatic	None
Error messages	Structured FieldError with source	Raw unmarshaling errors
Cloud sources	Vault, AWS, Consul, etcd, K8s (opt-in)	Community plugins
Extensibility	Custom Source interface	Provider interface

When to Choose

Choose confkit if…

You need multiple sources (YAML, env, flags, cloud)
You want defaults and validation built into struct tags
You care about clear error messages and debugging
You use cloud sources (Vault, AWS, Kubernetes, etcd)
You need secret redaction in logs and errors
You want a typed, generics API instead of interface{}

Choose envconfig if…

You only load config from environment variables
You want the absolute smallest library possible
You're OK writing validation code manually
You don't need cloud sources or file loading
Your config is simple — no defaults, no cross-field validation

Choose Viper if…

You need maximum flexibility and dynamic access
You're OK with stringly-typed GetInt/GetString
You have an existing Viper-based codebase
You need remote config (etcd, Consul) via the Viper ecosystem

Choose koanf if…

You need maximum modularity and customization
You want to compose your own pipeline from providers
You have specific low-level requirements
You're comfortable writing integration glue code

Side-by-Side: Full Example

confkit

type Config struct {
    Port     int    `env:"PORT" default:"8080" validate:"min=1,max=65535"`
    Database string `env:"DATABASE_URL" validate:"required" secret:"true"`
}

cfg, err := confkit.Load[Config](
    confkit.FromYAML("config.yaml"),
    confkit.FromEnv(),
)
if err != nil {
    log.Fatal(confkit.Explain(err))
    // Invalid configuration:
    //   DATABASE_URL: field is required (source: env)
}

envconfig

type Config struct {
    Port     int    `envconfig:"PORT"`
    Database string `envconfig:"DATABASE_URL"`
}

var cfg Config
envconfig.Process("", &cfg)
// Must manually set defaults
if cfg.Port == 0 {
    cfg.Port = 8080
}
// Must manually validate
if cfg.Port < 1 || cfg.Port > 65535 {
    log.Fatal("port out of range")
}
if cfg.Database == "" {
    log.Fatal("database required")
}