diff --git a/lib/util/stream_utils.js b/lib/util/stream_utils.js
index 908e48b6df..b3fb4c0a92 100644
--- a/lib/util/stream_utils.js
+++ b/lib/util/stream_utils.js
@@ -499,6 +499,33 @@ shaka.util.StreamUtils = class {
   }
 
 
+  /**
+   * Queries mediaCapabilities for the decoding info for that decoding config,
+   * and assigns it to the given variant.
+   * If that query has been done before, instead return a cached result.
+   * @param {!shaka.extern.Variant} variant
+   * @param {!MediaDecodingConfiguration} decodingConfig
+   * @private
+   */
+  static async getDecodingInfosForVariant_(variant, decodingConfig) {
+    try {
+      const cacheKey = JSON.stringify(decodingConfig);
+      const cache = shaka.util.StreamUtils.decodingConfigCache;
+      if (cache[cacheKey]) {
+        variant.decodingInfos.push(cache[cacheKey]);
+      } else {
+        const result =
+            await navigator.mediaCapabilities.decodingInfo(decodingConfig);
+        cache[cacheKey] = result;
+        variant.decodingInfos.push(result);
+      }
+    } catch (e) {
+      shaka.log.info('MediaCapabilities.decodingInfo() failed.',
+          JSON.stringify(decodingConfig), e);
+    }
+  }
+
+
   /**
    * Get the decodingInfo results of the variants via MediaCapabilities.
    * This should be called after the DrmEngine is created and configured, and
@@ -518,18 +545,6 @@ shaka.util.StreamUtils = class {
       return;
     }
 
-    const mediaCapabilities = navigator.mediaCapabilities;
-
-    const getVariantDecodingInfos = (async (variant, decodingConfig) => {
-      try {
-        const result = await mediaCapabilities.decodingInfo(decodingConfig);
-        variant.decodingInfos.push(result);
-      } catch (e) {
-        shaka.log.info('MediaCapabilities.decodingInfo() failed.',
-            JSON.stringify(decodingConfig), e);
-      }
-    });
-
     for (const variant of variants) {
       /** @type {!Array.<!MediaDecodingConfiguration>} */
       const decodingConfigs = shaka.util.StreamUtils.getDecodingConfigs_(
@@ -540,7 +555,8 @@ shaka.util.StreamUtils = class {
       // https://github.com/shaka-project/shaka-player/pull/4708#discussion_r1022581178
       for (const config of decodingConfigs) {
         // eslint-disable-next-line no-await-in-loop
-        await getVariantDecodingInfos(variant, config);
+        await shaka.util.StreamUtils.getDecodingInfosForVariant_(
+            variant, config);
       }
     }
   }
@@ -1578,6 +1594,16 @@ shaka.util.StreamUtils = class {
 };
 
 
+/**
+ * A cache of results from mediaCapabilities.decodingInfo, indexed by the
+ * (stringified) decodingConfig.
+ *
+ * @type {Object.<(!string), (!MediaCapabilitiesDecodingInfo)>}
+ * @export
+ */
+shaka.util.StreamUtils.decodingConfigCache = {};
+
+
 /** @private {number} */
 shaka.util.StreamUtils.nextTrackId_ = 0;
 
diff --git a/test/test/boot.js b/test/test/boot.js
index 99e7d70259..6df7f23fce 100644
--- a/test/test/boot.js
+++ b/test/test/boot.js
@@ -331,6 +331,11 @@ function configureJasmineEnvironment() {
     });
   }
 
+  // Reset decoding config cache after each test.
+  afterEach(() => {
+    shaka.util.StreamUtils.decodingConfigCache = {};
+  });
+
   // Code in karma-jasmine's adapter will malform test failures when the
   // expectation message contains a stack trace, losing the failure message and
   // mixing up the stack trace of the failure.  To avoid this, we modify