diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 2702903ee225..b1701a2864be 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -2203,6 +2203,7 @@ var gBrowserInit = {
         let globalHistoryOptions = undefined;
         let triggeringRemoteType = undefined;
         let forceAllowDataURI = false;
+        let wasSchemelessInput = false;
         if (window.arguments[1]) {
           if (!(window.arguments[1] instanceof Ci.nsIPropertyBag2)) {
             throw new Error(
@@ -2241,6 +2242,10 @@ var gBrowserInit = {
             forceAllowDataURI =
               extraOptions.getPropertyAsBool("forceAllowDataURI");
           }
+          if (extraOptions.hasKey("wasSchemelessInput")) {
+            wasSchemelessInput =
+              extraOptions.getPropertyAsBool("wasSchemelessInput");
+          }
         }
 
         try {
@@ -2264,6 +2269,7 @@ var gBrowserInit = {
             fromExternal,
             globalHistoryOptions,
             triggeringRemoteType,
+            wasSchemelessInput,
           });
         } catch (e) {
           console.error(e);
diff --git a/browser/base/content/tabbrowser.js b/browser/base/content/tabbrowser.js
index 1374eee9c7d8..f1d264d84fec 100644
--- a/browser/base/content/tabbrowser.js
+++ b/browser/base/content/tabbrowser.js
@@ -2590,6 +2590,7 @@
         insertTab = true,
         globalHistoryOptions,
         triggeringRemoteType,
+        wasSchemelessInput,
       } = {}
     ) {
       // all callers of addTab that pass a params object need to pass
@@ -2779,6 +2780,7 @@
           csp,
           globalHistoryOptions,
           triggeringRemoteType,
+          wasSchemelessInput,
         });
       }
 
@@ -3020,6 +3022,7 @@
         csp,
         globalHistoryOptions,
         triggeringRemoteType,
+        wasSchemelessInput,
       }
     ) {
       if (
@@ -3083,6 +3086,7 @@
             csp,
             globalHistoryOptions,
             triggeringRemoteType,
+            wasSchemelessInput,
           });
         } catch (ex) {
           console.error(ex);
diff --git a/browser/components/urlbar/UrlbarInput.sys.mjs b/browser/components/urlbar/UrlbarInput.sys.mjs
index 1fcc7b0bdfbb..a2b34555123c 100644
--- a/browser/components/urlbar/UrlbarInput.sys.mjs
+++ b/browser/components/urlbar/UrlbarInput.sys.mjs
@@ -741,6 +741,9 @@ export class UrlbarInput {
       isValidUrl = true;
     } catch (ex) {}
     if (isValidUrl) {
+      // Annotate if the untrimmed value contained a scheme, to later potentially
+      // be upgraded by schemeless HTTPS-First.
+      openParams.wasSchemelessInput = this.#isSchemeless(this.untrimmedValue);
       this._loadURL(url, event, where, openParams);
       return;
     }
@@ -788,13 +791,24 @@ export class UrlbarInput {
           if (this.isPrivate) {
             flags |= Ci.nsIURIFixup.FIXUP_FLAG_PRIVATE_CONTEXT;
           }
-          let { preferredURI: uri, postData } =
-            Services.uriFixup.getFixupURIInfo(url, flags);
+          let {
+            preferredURI: uri,
+            postData,
+            keywordAsSent,
+          } = Services.uriFixup.getFixupURIInfo(url, flags);
           if (
             where != "current" ||
             browser.lastLocationChange == lastLocationChange
           ) {
             openParams.postData = postData;
+            if (!keywordAsSent) {
+              // `uri` is not a search engine url, so we annotate if the untrimmed
+              // value contained a scheme, to potentially be later upgraded by
+              // schemeless HTTPS-First.
+              openParams.wasSchemelessInput = this.#isSchemeless(
+                this.untrimmedValue
+              );
+            }
             this._loadURL(uri.spec, event, where, openParams, null, browser);
           }
         }
@@ -992,30 +1006,36 @@ export class UrlbarInput {
 
     switch (result.type) {
       case lazy.UrlbarUtils.RESULT_TYPE.URL: {
-        // Bug 1578856: both the provider and the docshell run heuristics to
-        // decide how to handle a non-url string, either fixing it to a url, or
-        // searching for it.
-        // Some preferences can control the docshell behavior, for example
-        // if dns_first_for_single_words is true, the docshell looks up the word
-        // against the dns server, and either loads it as an url or searches for
-        // it, depending on the lookup result. The provider instead will always
-        // return a fixed url in this case, because URIFixup is synchronous and
-        // can't do a synchronous dns lookup. A possible long term solution
-        // would involve sharing the docshell logic with the provider, along
-        // with the dns lookup.
-        // For now, in this specific case, we'll override the result's url
-        // with the input value, and let it pass through to _loadURL(), and
-        // finally to the docshell.
-        // This also means that in some cases the heuristic result will show a
-        // Visit entry, but the docshell will instead execute a search. It's a
-        // rare case anyway, most likely to happen for enterprises customizing
-        // the urifixup prefs.
-        if (
-          result.heuristic &&
-          lazy.UrlbarPrefs.get("browser.fixup.dns_first_for_single_words") &&
-          lazy.UrlbarUtils.looksLikeSingleWordHost(originalUntrimmedValue)
-        ) {
-          url = originalUntrimmedValue;
+        if (result.heuristic) {
+          // Bug 1578856: both the provider and the docshell run heuristics to
+          // decide how to handle a non-url string, either fixing it to a url, or
+          // searching for it.
+          // Some preferences can control the docshell behavior, for example
+          // if dns_first_for_single_words is true, the docshell looks up the word
+          // against the dns server, and either loads it as an url or searches for
+          // it, depending on the lookup result. The provider instead will always
+          // return a fixed url in this case, because URIFixup is synchronous and
+          // can't do a synchronous dns lookup. A possible long term solution
+          // would involve sharing the docshell logic with the provider, along
+          // with the dns lookup.
+          // For now, in this specific case, we'll override the result's url
+          // with the input value, and let it pass through to _loadURL(), and
+          // finally to the docshell.
+          // This also means that in some cases the heuristic result will show a
+          // Visit entry, but the docshell will instead execute a search. It's a
+          // rare case anyway, most likely to happen for enterprises customizing
+          // the urifixup prefs.
+          if (
+            lazy.UrlbarPrefs.get("browser.fixup.dns_first_for_single_words") &&
+            lazy.UrlbarUtils.looksLikeSingleWordHost(originalUntrimmedValue)
+          ) {
+            url = originalUntrimmedValue;
+          }
+          // Annotate if the untrimmed value contained a scheme, to later potentially
+          // be upgraded by schemeless HTTPS-First.
+          openParams.wasSchemelessInput = this.#isSchemeless(
+            originalUntrimmedValue
+          );
         }
         break;
       }
@@ -2718,6 +2738,8 @@ export class UrlbarInput {
    *   The POST data associated with a search submission.
    * @param {boolean} [params.allowInheritPrincipal]
    *   Whether the principal can be inherited.
+   * @param {boolean} [params.wasSchemelessInput]
+   *   Whether the search/URL term was without an explicit scheme.
    * @param {object} [resultDetails]
    *   Details of the selected result, if any.
    * @param {UrlbarUtils.RESULT_TYPE} [resultDetails.type]
@@ -3948,6 +3970,18 @@ export class UrlbarInput {
     this._initPasteAndGo();
     this._initStripOnShare();
   }
+
+  /**
+   * @param {string} value A untrimmed address bar input.
+   * @returns {boolean}
+   *          `true` if the input doesn't start with a scheme relevant for
+   *          schemeless HTTPS-First (http://, https:// and file://).
+   */
+  #isSchemeless(value) {
+    return ["http://", "https://", "file://"].every(
+      scheme => !value.trim().startsWith(scheme)
+    );
+  }
 }
 
 /**
diff --git a/browser/modules/URILoadingHelper.sys.mjs b/browser/modules/URILoadingHelper.sys.mjs
index b8b8c180290d..232cf05b94c1 100644
--- a/browser/modules/URILoadingHelper.sys.mjs
+++ b/browser/modules/URILoadingHelper.sys.mjs
@@ -129,6 +129,12 @@ function openInWindow(url, params, sourceWindow) {
       );
     }
   }
+  if (params.wasSchemelessInput !== undefined) {
+    extraOptions.setPropertyAsBool(
+      "wasSchemelessInput",
+      params.wasSchemelessInput
+    );
+  }
 
   var allowThirdPartyFixupSupports = Cc[
     "@mozilla.org/supports-PRBool;1"
@@ -260,6 +266,7 @@ function openInCurrentTab(targetBrowser, url, uriObj, params) {
     hasValidUserGestureActivation,
     globalHistoryOptions,
     triggeringRemoteType,
+    wasSchemelessInput,
   } = params;
 
   targetBrowser.fixupAndLoadURIString(url, {
@@ -272,6 +279,7 @@ function openInCurrentTab(targetBrowser, url, uriObj, params) {
     hasValidUserGestureActivation,
     globalHistoryOptions,
     triggeringRemoteType,
+    wasSchemelessInput,
   });
   params.resolveOnContentBrowserCreated?.(targetBrowser);
 }
@@ -363,6 +371,8 @@ export const URILoadingHelper = {
    * @param {string}  params.charset
    *                  Character set to use for the load. Only honoured for tabs.
    *                  Legacy argument - do not use.
+   * @param {string}  params.wasSchemelessInput
+   *                  Whether the search/URL term was without an explicit scheme.
    *
    * Options relating to security, whether the load is allowed to happen,
    * and what cookie container to use for the load:
@@ -577,6 +587,7 @@ export const URILoadingHelper = {
           openerBrowser: params.openerBrowser,
           fromExternal: params.fromExternal,
           globalHistoryOptions,
+          wasSchemelessInput: params.wasSchemelessInput,
         });
         targetBrowser = tabUsedForLoad.linkedBrowser;
 
diff --git a/docshell/base/URIFixup.sys.mjs b/docshell/base/URIFixup.sys.mjs
index e68652c5c002..c42fb2efa8df 100644
--- a/docshell/base/URIFixup.sys.mjs
+++ b/docshell/base/URIFixup.sys.mjs
@@ -384,6 +384,7 @@ URIFixup.prototype = {
       if (uriWithProtocol) {
         info.fixedURI = uriWithProtocol;
         info.fixupChangedProtocol = true;
+        info.wasSchemelessInput = true;
         maybeSetAlternateFixedURI(info, fixupFlags);
         info.preferredURI = info.fixedURI;
         // Check if it's a forced visit. The user can enforce a visit by
@@ -686,6 +687,13 @@ URIFixupInfo.prototype = {
     return this._keywordAsSent || "";
   },
 
+  set wasSchemelessInput(changed) {
+    this._wasSchemelessInput = changed;
+  },
+  get wasSchemelessInput() {
+    return !!this._wasSchemelessInput;
+  },
+
   set fixupChangedProtocol(changed) {
     this._fixupChangedProtocol = changed;
   },
diff --git a/docshell/base/nsIURIFixup.idl b/docshell/base/nsIURIFixup.idl
index 9c63c79efafc..2261c0cb402d 100644
--- a/docshell/base/nsIURIFixup.idl
+++ b/docshell/base/nsIURIFixup.idl
@@ -49,6 +49,11 @@ interface nsIURIFixupInfo : nsISupports
    */
   attribute AString keywordAsSent;
 
+  /**
+   * Whether there was no protocol at all and we had to add one in the first place.
+   */
+  attribute boolean wasSchemelessInput;
+
   /**
    * Whether we changed the protocol instead of using one from the input as-is.
    */