diff --git a/package.json b/package.json
index de7847c34b..19cc5e6af1 100644
--- a/package.json
+++ b/package.json
@@ -125,6 +125,7 @@
     "karma-spec-reporter": "0.0.31",
     "karma-summary-reporter": "^1.5.1",
     "karma-webpack": "4.0.0-beta.0",
+    "loader-utils": "^1.2.3",
     "matrix-mock-request": "^1.2.2",
     "matrix-react-test-utils": "^0.2.0",
     "minimist": "^1.2.0",
diff --git a/scripts/copy-res.js b/scripts/copy-res.js
index cde96bc419..f1ed15b5d5 100755
--- a/scripts/copy-res.js
+++ b/scripts/copy-res.js
@@ -1,5 +1,7 @@
 #!/usr/bin/env node
 
+const loaderUtils = require("loader-utils");
+
 // copies the resources into the webapp directory.
 //
 
@@ -61,12 +63,6 @@ const COPY_LIST = [
     ["./config.json", "webapp", { directwatch: 1 }],
 ];
 
-INCLUDE_LANGS.forEach(function(l) {
-    COPY_LIST.push([
-        l.value, "webapp/i18n/", { lang: 1 },
-    ]);
-});
-
 const parseArgs = require('minimist');
 const Cpx = require('cpx');
 const chokidar = require('chokidar');
@@ -77,8 +73,8 @@ const argv = parseArgs(
     process.argv.slice(2), {}
 );
 
-var watch = argv.w;
-var verbose = argv.v;
+const watch = argv.w;
+const verbose = argv.v;
 
 function errCheck(err) {
     if (err) {
@@ -136,39 +132,11 @@ function next(i, err) {
                 .on('change', copy)
                 .on('ready', cb)
                 .on('error', errCheck);
-        } else if (opts.lang) {
-            const reactSdkFile = 'node_modules/matrix-react-sdk/src/i18n/strings/' + source + '.json';
-            const riotWebFile = 'src/i18n/strings/' + source + '.json';
-
-            // XXX: Use a debounce because for some reason if we read the language
-            // file immediately after the FS event is received, the file contents
-            // appears empty. Possibly https://github.com/nodejs/node/issues/6112
-            let makeLangDebouncer;
-            const makeLang = () => {
-                if (makeLangDebouncer) {
-                    clearTimeout(makeLangDebouncer);
-                }
-                makeLangDebouncer = setTimeout(() => {
-                    genLangFile(source, dest);
-                }, 500);
-            };
-
-            [reactSdkFile, riotWebFile].forEach(function(f) {
-                chokidar.watch(f)
-                    .on('add', makeLang)
-                    .on('change', makeLang)
-                    //.on('ready', cb)  We'd have to do this when both files are ready
-                    .on('error', errCheck);
-            });
-            next(i + 1, err);
         } else {
             cpx.on('watch-ready', cb);
             cpx.on("watch-error", cb);
             cpx.watch();
         }
-    } else if (opts.lang) {
-        genLangFile(source, dest);
-        next(i + 1, err);
     } else {
         cpx.copy(cb);
     }
@@ -195,21 +163,28 @@ function genLangFile(lang, dest) {
 
     translations = weblateToCounterpart(translations);
 
-    fs.writeFileSync(dest + lang + '.json', JSON.stringify(translations, null, 4));
+    const json = JSON.stringify(translations, null, 4);
+    const jsonBuffer = Buffer.from(json);
+    const digest = loaderUtils.getHashDigest(jsonBuffer, "sha512", "base64", 7);
+    const filename = `${lang}.${digest}.json`;
+
+    fs.writeFileSync(dest + filename, json);
     if (verbose) {
-        console.log("Generated language file: " + lang);
+        console.log("Generated language file: " + filename);
     }
+
+    return filename;
 }
 
-function genLangList() {
+function genLangList(langFileMap) {
     const languages = {};
     INCLUDE_LANGS.forEach(function(lang) {
         const normalizedLanguage = lang.value.toLowerCase().replace("_", "-");
         const languageParts = normalizedLanguage.split('-');
         if (languageParts.length == 2 && languageParts[0] == languageParts[1]) {
-            languages[languageParts[0]] = {'fileName': lang.value + '.json', 'label': lang.label};
+            languages[languageParts[0]] = {'fileName': langFileMap[lang.value], 'label': lang.label};
         } else {
-            languages[normalizedLanguage] = {'fileName': lang.value + '.json', 'label': lang.label};
+            languages[normalizedLanguage] = {'fileName': langFileMap[lang.value], 'label': lang.label};
         }
     });
     fs.writeFile('webapp/i18n/languages.json', JSON.stringify(languages, null, 4), function(err) {
@@ -257,5 +232,50 @@ function weblateToCounterpart(inTrs) {
     return outTrs;
 }
 
-genLangList();
+/**
+watch the input files for a given language,
+regenerate the file, adding its content-hashed filename to langFileMap
+and regenerating languages.json with the new filename
+*/
+function watchLanguage(lang, dest, langFileMap) {
+    const reactSdkFile = 'node_modules/matrix-react-sdk/src/i18n/strings/' + lang + '.json';
+    const riotWebFile = 'src/i18n/strings/' + lang + '.json';
+
+    // XXX: Use a debounce because for some reason if we read the language
+    // file immediately after the FS event is received, the file contents
+    // appears empty. Possibly https://github.com/nodejs/node/issues/6112
+    let makeLangDebouncer;
+    const makeLang = () => {
+        if (makeLangDebouncer) {
+            clearTimeout(makeLangDebouncer);
+        }
+        makeLangDebouncer = setTimeout(() => {
+            const filename = genLangFile(lang, dest);
+            langFileMap[lang]=filename;
+            genLangList(langFileMap);
+        }, 500);
+    };
+
+    [reactSdkFile, riotWebFile].forEach(function(f) {
+        chokidar.watch(f)
+            .on('add', makeLang)
+            .on('change', makeLang)
+            .on('error', errCheck);
+    });
+}
+
+// language resources
+const I18N_DEST = "webapp/i18n/";
+const I18N_FILENAME_MAP = INCLUDE_LANGS.reduce((m, l) => {
+    const filename = genLangFile(l.value, I18N_DEST);
+    m[l.value] = filename;
+    return m;
+}, {});
+genLangList(I18N_FILENAME_MAP);
+
+if (watch) {
+    INCLUDE_LANGS.forEach(l => watchLanguage(l.value, I18N_DEST, I18N_FILENAME_MAP));
+}
+
+// non-language resources
 next(0);