= cowboy_req:cert(3) == Name cowboy_req:cert - Client TLS certificate == Description [source,erlang] ---- cert(Req :: cowboy_req:req()) -> binary() | undefined ---- Return the peer's TLS certificate. Using the default configuration this function will always return `undefined`. You need to explicitly configure Cowboy to request the client certificate. To do this you need to set the `verify` transport option to `verify_peer`: [source,erlang] ---- {ok, _} = cowboy:start_tls(example, [ {port, 8443}, {certfile, "path/to/cert.pem"}, {verify, verify_peer} ], #{ env => #{dispatch => Dispatch} }). ---- You may also want to customize the `verify_fun` function. Please consult the `ssl` application's manual for more details. TCP connections do not allow a certificate and this function will therefore always return `undefined`. The certificate can also be obtained using pattern matching: [source,erlang] ---- #{cert := Cert} = Req. ---- == Arguments Req:: The Req object. == Return value The client TLS certificate. == Changelog * *2.1*: Function introduced. == Examples .Get the client TLS certificate. [source,erlang] ---- Cert = cowboy_req:cert(Req). ---- == See also link:man:cowboy_req(3)[cowboy_req(3)], link:man:cowboy_req:peer(3)[cowboy_req:peer(3)], link:man:cowboy_req:sock(3)[cowboy_req:sock(3)]