Cargo Features

tracing = { version = "0.1.40", default-features = false, features = ["max_level_warn", "max_level_trace", "release_max_level_error", "release_max_level_info", "release_max_level_trace", "async-await", "std", "log-always", "attributes", "valuable"] }
default = attributes, std

These default features are set whenever tracing is added without default-features = false somewhere in the dependency tree.

max_level_off max_level_error max_level_warn
max_level_info max_level_debug max_level_trace
release_max_level_off release_max_level_error
release_max_level_warn release_max_level_info
release_max_level_debug release_max_level_trace

This feature flag is no longer necessary.

std default

Enables std of tracing-core

Affects subscriber::with_default, subscriber::set_default

log-always = log
attributes default = tracing-attributes

Enables valuable of tracing-core

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features.

log log-always?

Affects tracing::log

tracing-attributes attributes