diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index d82df9e93964..8ccbbe81ea5a 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5318,7 +5318,7 @@ pref("network.captive-portal-service.backoffFactor", "5.0");
 pref("network.captive-portal-service.enabled", false);
 
 // DNS Trusted Recursive Resolver
-// 0 - off, 1 - race, 2 TRR first, 3 TRR only, 4 shadow
+// 0 - default off, 1 - race, 2 TRR first, 3 TRR only, 4 shadow, 5 off by choice
 pref("network.trr.mode", 0);
 // DNS-over-HTTP service to use, must be HTTPS://
 pref("network.trr.uri", "");
diff --git a/netwerk/dns/TRRService.cpp b/netwerk/dns/TRRService.cpp
index 9e17669fac1e..4f048b8a851e 100644
--- a/netwerk/dns/TRRService.cpp
+++ b/netwerk/dns/TRRService.cpp
@@ -324,7 +324,7 @@ TRRService::Observe(nsISupports *aSubject,
 void
 TRRService::MaybeConfirm()
 {
-  if ((mMode == MODE_NATIVEONLY) || mConfirmer ||
+  if (TRR_DISABLED(mMode) || mConfirmer ||
       mConfirmationState != CONFIRM_TRYING) {
     LOG(("TRRService:MaybeConfirm mode=%d, mConfirmer=%p mConfirmationState=%d\n",
          (int)mMode, (void *)mConfirmer, (int)mConfirmationState));
@@ -351,7 +351,7 @@ bool
 TRRService::MaybeBootstrap(const nsACString &aPossible, nsACString &aResult)
 {
   MutexAutoLock lock(mLock);
-  if ((mMode == MODE_NATIVEONLY) || mBootstrapAddr.IsEmpty()) {
+  if (TRR_DISABLED(mMode) || mBootstrapAddr.IsEmpty()) {
     return false;
   }
 
diff --git a/netwerk/dns/nsHostResolver.cpp b/netwerk/dns/nsHostResolver.cpp
index 21cd99cd9544..4282d8989a27 100644
--- a/netwerk/dns/nsHostResolver.cpp
+++ b/netwerk/dns/nsHostResolver.cpp
@@ -314,6 +314,9 @@ nsHostRecord::ResolveComplete()
     case MODE_SHADOW:
         AccumulateCategorical(Telemetry::LABELS_DNS_LOOKUP_ALGORITHM::trrShadow);
         break;
+    case MODE_TRROFF:
+        AccumulateCategorical(Telemetry::LABELS_DNS_LOOKUP_ALGORITHM::trrOff);
+        break;
     }
 
     if (mTRRUsed && !mTRRSuccess && mNativeSuccess && gTRRService) {
@@ -1267,12 +1270,12 @@ nsHostResolver::NameLookup(nsHostRecord *rec)
         mode = MODE_NATIVEONLY;
     }
 
-    if (mode != MODE_NATIVEONLY) {
+    if (!TRR_DISABLED(mode)) {
         rv = TrrLookup(rec);
     }
 
     if ((mode == MODE_PARALLEL) ||
-        (mode == MODE_NATIVEONLY) ||
+        TRR_DISABLED(mode) ||
         (mode == MODE_SHADOW) ||
         ((mode == MODE_TRRFIRST) && NS_FAILED(rv))) {
         rv = NativeLookup(rec);
diff --git a/netwerk/dns/nsHostResolver.h b/netwerk/dns/nsHostResolver.h
index 503d87016cd4..84ef8c034d88 100644
--- a/netwerk/dns/nsHostResolver.h
+++ b/netwerk/dns/nsHostResolver.h
@@ -29,14 +29,17 @@ class nsResolveHostCallback;
 namespace mozilla { namespace net {
 class TRR;
 enum ResolverMode {
-  MODE_NATIVEONLY, // TRR OFF
-  MODE_PARALLEL,   // race and use the first response
-  MODE_TRRFIRST,   // fallback to native on TRR failure
-  MODE_TRRONLY,    // don't even fallback
-  MODE_SHADOW      // race for stats, but always use native result
+  MODE_NATIVEONLY, // 0 - TRR OFF (by default)
+  MODE_PARALLEL,   // 1 - race and use the first response
+  MODE_TRRFIRST,   // 2 - fallback to native on TRR failure
+  MODE_TRRONLY,    // 3 - don't even fallback
+  MODE_SHADOW,     // 4 - race for stats, but always use native result
+  MODE_TRROFF      // 5 - identical to MODE_NATIVEONLY but explicitly selected
 };
 } }
 
+#define TRR_DISABLED(x) (((x) == MODE_NATIVEONLY) || ((x) == MODE_TRROFF))
+
 extern mozilla::Atomic<bool, mozilla::Relaxed> gNativeIsLocalhost;
 
 #define MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY  3
diff --git a/toolkit/components/telemetry/Histograms.json b/toolkit/components/telemetry/Histograms.json
index be27c26e5086..a988c054bc32 100644
--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -3294,7 +3294,7 @@
     "alert_emails": ["necko@mozilla.com", "dstenberg@mozilla.com"],
     "expires_in_version": "never",
     "kind": "categorical",
-    "labels": ["nativeOnly", "trrRace", "trrFirst", "trrOnly", "trrShadow"],
+    "labels": ["nativeOnly", "trrRace", "trrFirst", "trrOnly", "trrShadow", "trrOff"],
     "bug_numbers": [1434852],
     "description": "DNS: lookup algorithm"
   },