diff --git a/demo/markdownlint-browser.js b/demo/markdownlint-browser.js
index 5fb5f0c7..087bc320 100644
--- a/demo/markdownlint-browser.js
+++ b/demo/markdownlint-browser.js
@@ -1608,65 +1608,63 @@ function lintInput(options, synchronous, callback) {
     var fs = options.fs || __webpack_require__(/*! fs */ "?ec0a");
     var results = newResults(ruleList);
     var done = false;
-    // Linting of strings is always synchronous
-    var syncItem = null;
-    // eslint-disable-next-line jsdoc/require-jsdoc
-    function syncCallback(err, result) {
-        if (err) {
-            done = true;
-            return callback(err);
-        }
-        results[syncItem] = result;
-        return null;
-    }
-    while (!done && (syncItem = stringsKeys.shift())) {
-        lintContent(ruleList, syncItem, strings[syncItem] || "", md, config, frontMatter, handleRuleFailures, noInlineConfig, resultVersion, syncCallback);
-    }
-    if (synchronous) {
-        // Lint files synchronously
-        while (!done && (syncItem = files.shift())) {
-            lintFile(ruleList, syncItem, md, config, frontMatter, handleRuleFailures, noInlineConfig, resultVersion, fs, synchronous, syncCallback);
-        }
-        return done || callback(null, results);
-    }
-    // Lint files asynchronously
     var concurrency = 0;
     // eslint-disable-next-line jsdoc/require-jsdoc
-    function lintConcurrently() {
-        var asyncItem = files.shift();
-        if (done) {
-            // Nothing to do
+    function lintWorker() {
+        var currentItem = null;
+        // eslint-disable-next-line jsdoc/require-jsdoc
+        function lintWorkerCallback(err, result) {
+            concurrency--;
+            if (err) {
+                done = true;
+                return callback(err);
+            }
+            results[currentItem] = result;
+            if (!synchronous) {
+                lintWorker();
+            }
+            return null;
         }
-        else if (asyncItem) {
+        if (done) {
+            // Abort for error or nothing left to do
+        }
+        else if (files.length > 0) {
+            // Lint next file
             concurrency++;
-            lintFile(ruleList, asyncItem, md, config, frontMatter, handleRuleFailures, noInlineConfig, resultVersion, fs, synchronous, function (err, result) {
-                concurrency--;
-                if (err) {
-                    done = true;
-                    return callback(err);
-                }
-                results[asyncItem] = result;
-                lintConcurrently();
-                return null;
-            });
+            currentItem = files.shift();
+            lintFile(ruleList, currentItem, md, config, frontMatter, handleRuleFailures, noInlineConfig, resultVersion, fs, synchronous, lintWorkerCallback);
+        }
+        else if (stringsKeys.length > 0) {
+            // Lint next string
+            concurrency++;
+            currentItem = stringsKeys.shift();
+            lintContent(ruleList, currentItem, strings[currentItem] || "", md, config, frontMatter, handleRuleFailures, noInlineConfig, resultVersion, lintWorkerCallback);
         }
         else if (concurrency === 0) {
+            // Finish
             done = true;
             return callback(null, results);
         }
         return null;
     }
-    // Testing on a Raspberry Pi 4 Model B with an artificial 5ms file access
-    // delay suggests that a concurrency factor of 8 can eliminate the impact
-    // of that delay (i.e., total time is the same as with no delay).
-    lintConcurrently();
-    lintConcurrently();
-    lintConcurrently();
-    lintConcurrently();
-    lintConcurrently();
-    lintConcurrently();
-    lintConcurrently();
-    lintConcurrently();
+    if (synchronous) {
+        while (!done) {
+            lintWorker();
+        }
+    }
+    else {
+        // Testing on a Raspberry Pi 4 Model B with an artificial 5ms file access
+        // delay suggests that a concurrency factor of 8 can eliminate the impact
+        // of that delay (i.e., total time is the same as with no delay).
+        lintWorker();
+        lintWorker();
+        lintWorker();
+        lintWorker();
+        lintWorker();
+        lintWorker();
+        lintWorker();
+        lintWorker();
+    }
     return null;
 }
 /**
diff --git a/lib/markdownlint.js b/lib/markdownlint.js
index 5ce2b17b..10eeb4b3 100644
--- a/lib/markdownlint.js
+++ b/lib/markdownlint.js
@@ -749,62 +749,32 @@ function lintInput(options, synchronous, callback) {
   const fs = options.fs || require("fs");
   const results = newResults(ruleList);
   let done = false;
-  // Linting of strings is always synchronous
-  let syncItem = null;
-  // eslint-disable-next-line jsdoc/require-jsdoc
-  function syncCallback(err, result) {
-    if (err) {
-      done = true;
-      return callback(err);
-    }
-    results[syncItem] = result;
-    return null;
-  }
-  while (!done && (syncItem = stringsKeys.shift())) {
-    lintContent(
-      ruleList,
-      syncItem,
-      strings[syncItem] || "",
-      md,
-      config,
-      frontMatter,
-      handleRuleFailures,
-      noInlineConfig,
-      resultVersion,
-      syncCallback
-    );
-  }
-  if (synchronous) {
-    // Lint files synchronously
-    while (!done && (syncItem = files.shift())) {
-      lintFile(
-        ruleList,
-        syncItem,
-        md,
-        config,
-        frontMatter,
-        handleRuleFailures,
-        noInlineConfig,
-        resultVersion,
-        fs,
-        synchronous,
-        syncCallback
-      );
-    }
-    return done || callback(null, results);
-  }
-  // Lint files asynchronously
   let concurrency = 0;
   // eslint-disable-next-line jsdoc/require-jsdoc
-  function lintConcurrently() {
-    const asyncItem = files.shift();
+  function lintWorker() {
+    let currentItem = null;
+    // eslint-disable-next-line jsdoc/require-jsdoc
+    function lintWorkerCallback(err, result) {
+      concurrency--;
+      if (err) {
+        done = true;
+        return callback(err);
+      }
+      results[currentItem] = result;
+      if (!synchronous) {
+        lintWorker();
+      }
+      return null;
+    }
     if (done) {
-      // Nothing to do
-    } else if (asyncItem) {
+      // Abort for error or nothing left to do
+    } else if (files.length > 0) {
+      // Lint next file
       concurrency++;
+      currentItem = files.shift();
       lintFile(
         ruleList,
-        asyncItem,
+        currentItem,
         md,
         config,
         frontMatter,
@@ -813,34 +783,48 @@ function lintInput(options, synchronous, callback) {
         resultVersion,
         fs,
         synchronous,
-        (err, result) => {
-          concurrency--;
-          if (err) {
-            done = true;
-            return callback(err);
-          }
-          results[asyncItem] = result;
-          lintConcurrently();
-          return null;
-        }
+        lintWorkerCallback
+      );
+    } else if (stringsKeys.length > 0) {
+      // Lint next string
+      concurrency++;
+      currentItem = stringsKeys.shift();
+      lintContent(
+        ruleList,
+        currentItem,
+        strings[currentItem] || "",
+        md,
+        config,
+        frontMatter,
+        handleRuleFailures,
+        noInlineConfig,
+        resultVersion,
+        lintWorkerCallback
       );
     } else if (concurrency === 0) {
+      // Finish
       done = true;
       return callback(null, results);
     }
     return null;
   }
-  // Testing on a Raspberry Pi 4 Model B with an artificial 5ms file access
-  // delay suggests that a concurrency factor of 8 can eliminate the impact
-  // of that delay (i.e., total time is the same as with no delay).
-  lintConcurrently();
-  lintConcurrently();
-  lintConcurrently();
-  lintConcurrently();
-  lintConcurrently();
-  lintConcurrently();
-  lintConcurrently();
-  lintConcurrently();
+  if (synchronous) {
+    while (!done) {
+      lintWorker();
+    }
+  } else {
+    // Testing on a Raspberry Pi 4 Model B with an artificial 5ms file access
+    // delay suggests that a concurrency factor of 8 can eliminate the impact
+    // of that delay (i.e., total time is the same as with no delay).
+    lintWorker();
+    lintWorker();
+    lintWorker();
+    lintWorker();
+    lintWorker();
+    lintWorker();
+    lintWorker();
+    lintWorker();
+  }
   return null;
 }