--- a/testing/geckodriver/CHANGES.md
+++ b/testing/geckodriver/CHANGES.md
@@ -9,16 +9,19 @@ Unreleased
 ### Changed
 
 - HTTP status code for the [`StaleElementReference`] error changed
   from 400 (Bad Request) to 404 (Not Found)
 
 - Backtraces from geckodriver no longer substitute for missing
   Marionette stacktraces
 
+- Output from Firefox is now quenched by default.  It can be
+  resurfaced by increasing the logging verbosity to config level or below.
+
 
 0.19.1 (2017-10-30)
 -------------------
 
 ### Changed
 
 - Search suggestions in the location bar turned off as not to
   trigger network connections

--- a/testing/geckodriver/src/logging.rs
+++ b/testing/geckodriver/src/logging.rs
@@ -18,27 +18,28 @@ lazy_static! {
     static ref ATOMIC_DRAIN: AtomicSwitchCtrl<io::Error> = AtomicSwitch::new(
         slog::Discard.map_err(|_| io::Error::new(io::ErrorKind::Other, "should not happen"))
     ).ctrl();
     static ref FIRST_RUN: AtomicBool = AtomicBool::new(true);
 }
 
 static DEFAULT_LEVEL: &'static LogLevel = &LogLevel::Info;
 
-/// Logger levels from [Log.jsm]
-/// (https://developer.mozilla.org/en/docs/Mozilla/JavaScript_code_modules/Log.jsm).
-#[derive(Debug, Clone)]
+/// Logger levels from [Log.jsm].
+///
+/// [Log.jsm]: https://developer.mozilla.org/en/docs/Mozilla/JavaScript_code_modules/Log.jsm
+#[derive(Debug, Eq, Clone, Ord, PartialOrd, PartialEq)]
 pub enum LogLevel {
-    Fatal,
-    Error,
-    Warn,
-    Info,
-    Config,
-    Debug,
-    Trace,
+    Fatal = 70,
+    Error = 60,
+    Warn = 50,
+    Info = 40,
+    Config = 30,
+    Debug = 20,
+    Trace = 10,
 }
 
 impl fmt::Display for LogLevel {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let s = match *self {
             LogLevel::Fatal => "FATAL",
             LogLevel::Error => "ERROR",
             LogLevel::Warn => "WARN",
@@ -143,17 +144,37 @@ impl Format for GeckoFormat {
 /// Produces a 13-digit Unix Epoch timestamp similar to Gecko.
 fn format_ts(ts: DateTime<Local>) -> String {
     format!("{}{:03}", ts.timestamp(), ts.timestamp_subsec_millis())
 }
 
 #[cfg(test)]
 mod tests {
     use chrono::Local;
-    use super::format_ts;
+    use super::{LogLevel, format_ts};
+
+    #[test]
+    fn test_log_level_cmp() {
+        use self::LogLevel::*;
+
+        assert!(Fatal == Fatal);
+        assert!(Error == Error);
+        assert!(Warn == Warn);
+        assert!(Info == Info);
+        assert!(Config == Config);
+        assert!(Debug == Debug);
+        assert!(Trace == Trace);
+
+        assert!(Fatal > Error);
+        assert!(Error > Warn);
+        assert!(Warn > Info);
+        assert!(Info > Config);
+        assert!(Config > Debug);
+        assert!(Debug > Trace);
+    }
 
     #[test]
     fn test_format_ts() {
         let ts = Local::now();
         let s = format_ts(ts);
         assert_eq!(s.len(), 13);
     }
 }

--- a/testing/geckodriver/src/marionette.rs
+++ b/testing/geckodriver/src/marionette.rs
@@ -1,14 +1,14 @@
 use hyper::method::Method;
 use logging;
 use logging::LogLevel;
 use mozprofile::preferences::Pref;
 use mozprofile::profile::Profile;
-use mozrunner::runner::{Runner, FirefoxRunner};
+use mozrunner::runner::{FirefoxRunner, Runner, Stdio};
 use regex::Captures;
 use rustc_serialize::base64::FromBase64;
 use rustc_serialize::json;
 use rustc_serialize::json::{Json, ToJson};
 use std::collections::BTreeMap;
 use std::env;
 use std::error::Error;
 use std::fs::File;
@@ -453,17 +453,23 @@ impl MarionetteHandler {
 
         // https://developer.mozilla.org/docs/Environment_variables_affecting_crash_reporting
         runner.envs().insert("MOZ_CRASHREPORTER".to_string(), "1".to_string());
         runner.envs().insert("MOZ_CRASHREPORTER_NO_REPORT".to_string(), "1".to_string());
         runner.envs().insert("MOZ_CRASHREPORTER_SHUTDOWN".to_string(), "1".to_string());
 
         if let Some(args) = options.args.take() {
             runner.args().extend(args);
-        };
+        }
+
+        if let Some(level) = self.current_log_level.take() {
+            if level < LogLevel::Info {
+                runner.stdio = Stdio::Inherit;
+            }
+        }
 
         try!(self.set_prefs(port, &mut runner.profile, custom_profile, options.prefs)
             .map_err(|e| {
                 WebDriverError::new(ErrorStatus::SessionNotCreated,
                                     format!("Failed to set preferences: {}", e))
             }));
 
         try!(runner.start()