Cargo Features

multer has no features set by default.

multer = { version = "3.1.0", features = ["all", "json", "tokio-io", "log"] }
all = json
json all? = serde, serde_json
tokio-io = tokio, tokio-util

Enables log

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

serde json?
serde_json json?
tokio tokio-io?
tokio-util tokio-io?