diff --git a/lib/languages.js b/lib/languages.js
index 449d280412..9c93689f31 100644
--- a/lib/languages.js
+++ b/lib/languages.js
@@ -25,6 +25,8 @@ exports.LANGUAGE_ALIASES = {
     "c#": Language.csharp,
     kotlin: Language.java,
     typescript: Language.javascript,
+    "javascript-typescript": Language.javascript,
+    "java-kotlin": Language.java,
 };
 /**
  * Translate from user input or GitHub's API names for languages to CodeQL's
diff --git a/lib/languages.js.map b/lib/languages.js.map
index e2d6a156eb..b2fcb525c9 100644
--- a/lib/languages.js.map
+++ b/lib/languages.js.map
@@ -1 +1 @@
-{"version":3,"file":"languages.js","sourceRoot":"","sources":["../src/languages.ts"],"names":[],"mappings":";;;AAgCA,sCAgBC;AAED,4CAQC;AAED,8CAEC;AA9DD,wCAAwC;AACxC,IAAY,QAWX;AAXD,WAAY,QAAQ;IAClB,+BAAmB,CAAA;IACnB,6BAAiB,CAAA;IACjB,uBAAW,CAAA;IACX,qBAAS,CAAA;IACT,yBAAa,CAAA;IACb,qCAAyB,CAAA;IACzB,6BAAiB,CAAA;IACjB,yBAAa,CAAA;IACb,yBAAa,CAAA;IACb,2BAAe,CAAA;AACjB,CAAC,EAXW,QAAQ,wBAAR,QAAQ,QAWnB;AAED,iCAAiC;AACpB,QAAA,gBAAgB,GAAiC;IAC5D,CAAC,EAAE,QAAQ,CAAC,GAAG;IACf,KAAK,EAAE,QAAQ,CAAC,GAAG;IACnB,IAAI,EAAE,QAAQ,CAAC,MAAM;IACrB,MAAM,EAAE,QAAQ,CAAC,IAAI;IACrB,UAAU,EAAE,QAAQ,CAAC,UAAU;CAChC,CAAC;AAEF;;;;;;;;GAQG;AACH,SAAgB,aAAa,CAAC,QAAgB;IAC5C,0BAA0B;IAC1B,QAAQ,GAAG,QAAQ,CAAC,IAAI,EAAE,CAAC,WAAW,EAAE,CAAC;IAEzC,6BAA6B;IAC7B,IAAI,QAAQ,IAAI,QAAQ,EAAE,CAAC;QACzB,OAAO,QAAoB,CAAC;IAC9B,CAAC;IAED,iEAAiE;IACjE,oCAAoC;IACpC,IAAI,QAAQ,IAAI,wBAAgB,EAAE,CAAC;QACjC,OAAO,wBAAgB,CAAC,QAAQ,CAAC,CAAC;IACpC,CAAC;IAED,OAAO,SAAS,CAAC;AACnB,CAAC;AAED,SAAgB,gBAAgB,CAAC,QAAkB;IACjD,OAAO;QACL,QAAQ,CAAC,GAAG;QACZ,QAAQ,CAAC,MAAM;QACf,QAAQ,CAAC,EAAE;QACX,QAAQ,CAAC,IAAI;QACb,QAAQ,CAAC,KAAK;KACf,CAAC,QAAQ,CAAC,QAAQ,CAAC,CAAC;AACvB,CAAC;AAED,SAAgB,iBAAiB,CAAC,QAAkB;IAClD,OAAO,CAAC,gBAAgB,CAAC,QAAQ,CAAC,CAAC;AACrC,CAAC"}
\ No newline at end of file
+{"version":3,"file":"languages.js","sourceRoot":"","sources":["../src/languages.ts"],"names":[],"mappings":";;;AAkCA,sCAgBC;AAED,4CAQC;AAED,8CAEC;AAhED,wCAAwC;AACxC,IAAY,QAWX;AAXD,WAAY,QAAQ;IAClB,+BAAmB,CAAA;IACnB,6BAAiB,CAAA;IACjB,uBAAW,CAAA;IACX,qBAAS,CAAA;IACT,yBAAa,CAAA;IACb,qCAAyB,CAAA;IACzB,6BAAiB,CAAA;IACjB,yBAAa,CAAA;IACb,yBAAa,CAAA;IACb,2BAAe,CAAA;AACjB,CAAC,EAXW,QAAQ,wBAAR,QAAQ,QAWnB;AAED,iCAAiC;AACpB,QAAA,gBAAgB,GAAiC;IAC5D,CAAC,EAAE,QAAQ,CAAC,GAAG;IACf,KAAK,EAAE,QAAQ,CAAC,GAAG;IACnB,IAAI,EAAE,QAAQ,CAAC,MAAM;IACrB,MAAM,EAAE,QAAQ,CAAC,IAAI;IACrB,UAAU,EAAE,QAAQ,CAAC,UAAU;IAC/B,uBAAuB,EAAE,QAAQ,CAAC,UAAU;IAC5C,aAAa,EAAE,QAAQ,CAAC,IAAI;CAC7B,CAAC;AAEF;;;;;;;;GAQG;AACH,SAAgB,aAAa,CAAC,QAAgB;IAC5C,0BAA0B;IAC1B,QAAQ,GAAG,QAAQ,CAAC,IAAI,EAAE,CAAC,WAAW,EAAE,CAAC;IAEzC,6BAA6B;IAC7B,IAAI,QAAQ,IAAI,QAAQ,EAAE,CAAC;QACzB,OAAO,QAAoB,CAAC;IAC9B,CAAC;IAED,iEAAiE;IACjE,oCAAoC;IACpC,IAAI,QAAQ,IAAI,wBAAgB,EAAE,CAAC;QACjC,OAAO,wBAAgB,CAAC,QAAQ,CAAC,CAAC;IACpC,CAAC;IAED,OAAO,SAAS,CAAC;AACnB,CAAC;AAED,SAAgB,gBAAgB,CAAC,QAAkB;IACjD,OAAO;QACL,QAAQ,CAAC,GAAG;QACZ,QAAQ,CAAC,MAAM;QACf,QAAQ,CAAC,EAAE;QACX,QAAQ,CAAC,IAAI;QACb,QAAQ,CAAC,KAAK;KACf,CAAC,QAAQ,CAAC,QAAQ,CAAC,CAAC;AACvB,CAAC;AAED,SAAgB,iBAAiB,CAAC,QAAkB;IAClD,OAAO,CAAC,gBAAgB,CAAC,QAAQ,CAAC,CAAC;AACrC,CAAC"}
\ No newline at end of file
diff --git a/lib/start-proxy-action.js b/lib/start-proxy-action.js
index 5c52f46522..6a2030ea9d 100644
--- a/lib/start-proxy-action.js
+++ b/lib/start-proxy-action.js
@@ -39,6 +39,7 @@ const core = __importStar(require("@actions/core"));
 const toolcache = __importStar(require("@actions/tool-cache"));
 const node_forge_1 = require("node-forge");
 const actionsUtil = __importStar(require("./actions-util"));
+const languages_1 = require("./languages");
 const logging_1 = require("./logging");
 const util = __importStar(require("./util"));
 const UPDATEJOB_PROXY = "update-job-proxy";
@@ -47,6 +48,19 @@ const UPDATEJOB_PROXY_URL_PREFIX = "https://github.com/github/codeql-action/rele
 const PROXY_USER = "proxy_user";
 const KEY_SIZE = 2048;
 const KEY_EXPIRY_YEARS = 2;
+const LANGUAGE_TO_REGISTRY_TYPE = {
+    java: "maven_repository",
+    csharp: "nuget_feed",
+    javascript: "npm_registry",
+    python: "python_index",
+    ruby: "rubygems_server",
+    rust: "cargo_registry",
+    // We do not have an established proxy type for these languages, thus leaving empty.
+    actions: "",
+    cpp: "",
+    go: "",
+    swift: "",
+};
 const CERT_SUBJECT = [
     {
         name: "commonName",
@@ -170,6 +184,11 @@ async function startProxy(binPath, config, logFilePath, logger) {
 function getCredentials(logger) {
     const registriesCredentials = actionsUtil.getOptionalInput("registries_credentials");
     const registrySecrets = actionsUtil.getOptionalInput("registry_secrets");
+    const languageString = actionsUtil.getOptionalInput("language");
+    const language = languageString ? (0, languages_1.parseLanguage)(languageString) : undefined;
+    const registryTypeForLanguage = language
+        ? LANGUAGE_TO_REGISTRY_TYPE[language]
+        : undefined;
     let credentialsStr;
     if (registriesCredentials !== undefined) {
         logger.info(`Using registries_credentials input.`);
@@ -190,6 +209,11 @@ function getCredentials(logger) {
         if (e.url === undefined && e.host === undefined) {
             throw new Error("Invalid credentials - must specify host or url");
         }
+        // Filter credentials based on language if specified. `type` is the registry type.
+        // E.g., "maven_feed" for Java/Kotlin, "nuget_repository" for C#.
+        if (e.type !== registryTypeForLanguage) {
+            continue;
+        }
         out.push({
             type: e.type,
             host: e.host,
diff --git a/lib/start-proxy-action.js.map b/lib/start-proxy-action.js.map
index 6e26998891..5e4bbc8f79 100644
--- a/lib/start-proxy-action.js.map
+++ b/lib/start-proxy-action.js.map
@@ -1 +1 @@
-{"version":3,"file":"start-proxy-action.js","sourceRoot":"","sources":["../src/start-proxy-action.ts"],"names":[],"mappings":";;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;AAAA,iDAAoD;AACpD,2CAA6B;AAE7B,oDAAsC;AACtC,+DAAiD;AACjD,2CAAiC;AAEjC,4DAA8C;AAC9C,uCAAqD;AACrD,6CAA+B;AAE/B,MAAM,eAAe,GAAG,kBAAkB,CAAC;AAC3C,MAAM,uBAAuB,GAAG,qBAAqB,CAAC;AACtD,MAAM,0BAA0B,GAC9B,kFAAkF,CAAC;AACrF,MAAM,UAAU,GAAG,YAAY,CAAC;AAChC,MAAM,QAAQ,GAAG,IAAI,CAAC;AACtB,MAAM,gBAAgB,GAAG,CAAC,CAAC;AA2B3B,MAAM,YAAY,GAAG;IACnB;QACE,IAAI,EAAE,YAAY;QAClB,KAAK,EAAE,wBAAwB;KAChC;IACD;QACE,IAAI,EAAE,kBAAkB;QACxB,KAAK,EAAE,aAAa;KACrB;IACD;QACE,SAAS,EAAE,IAAI;QACf,KAAK,EAAE,YAAY;KACpB;IACD;QACE,IAAI,EAAE,aAAa;QACnB,KAAK,EAAE,IAAI;KACZ;IACD;QACE,SAAS,EAAE,IAAI;QACf,KAAK,EAAE,YAAY;KACpB;IACD;QACE,IAAI,EAAE,cAAc;QACpB,KAAK,EAAE,eAAe;KACvB;CACF,CAAC;AAEF,SAAS,4BAA4B;IACnC,MAAM,IAAI,GAAG,gBAAG,CAAC,GAAG,CAAC,eAAe,CAAC,QAAQ,CAAC,CAAC;IAC/C,MAAM,IAAI,GAAG,gBAAG,CAAC,iBAAiB,EAAE,CAAC;IACrC,IAAI,CAAC,SAAS,GAAG,IAAI,CAAC,SAAS,CAAC;IAChC,IAAI,CAAC,YAAY,GAAG,IAAI,CAAC;IACzB,IAAI,CAAC,QAAQ,CAAC,SAAS,GAAG,IAAI,IAAI,EAAE,CAAC;IACrC,IAAI,CAAC,QAAQ,CAAC,QAAQ,GAAG,IAAI,IAAI,EAAE,CAAC;IACpC,IAAI,CAAC,QAAQ,CAAC,QAAQ,CAAC,WAAW,CAChC,IAAI,CAAC,QAAQ,CAAC,SAAS,CAAC,WAAW,EAAE,GAAG,gBAAgB,CACzD,CAAC;IAEF,IAAI,CAAC,UAAU,CAAC,YAAY,CAAC,CAAC;IAC9B,IAAI,CAAC,SAAS,CAAC,YAAY,CAAC,CAAC;IAC7B,IAAI,CAAC,aAAa,CAAC,CAAC,EAAE,IAAI,EAAE,kBAAkB,EAAE,EAAE,EAAE,IAAI,EAAE,CAAC,CAAC,CAAC;IAC7D,IAAI,CAAC,IAAI,CAAC,IAAI,CAAC,UAAU,CAAC,CAAC;IAE3B,MAAM,GAAG,GAAG,gBAAG,CAAC,gBAAgB,CAAC,IAAI,CAAC,CAAC;IACvC,MAAM,GAAG,GAAG,gBAAG,CAAC,eAAe,CAAC,IAAI,CAAC,UAAU,CAAC,CAAC;IACjD,OAAO,EAAE,IAAI,EAAE,GAAG,EAAE,GAAG,EAAE,CAAC;AAC5B,CAAC;AAED,KAAK,UAAU,UAAU;IACvB,6CAA6C;IAC7C,WAAW,CAAC,aAAa,EAAE,CAAC;IAE5B,MAAM,MAAM,GAAG,IAAA,0BAAgB,GAAE,CAAC;IAElC,8BAA8B;IAC9B,MAAM,OAAO,GAAG,WAAW,CAAC,qBAAqB,EAAE,CAAC;IACpD,MAAM,gBAAgB,GAAG,IAAI,CAAC,OAAO,CAAC,OAAO,EAAE,WAAW,CAAC,CAAC;IAC5D,IAAI,CAAC,SAAS,CAAC,gBAAgB,EAAE,gBAAgB,CAAC,CAAC;IAEnD,gCAAgC;IAChC,MAAM,WAAW,GAAG,cAAc,CAAC,MAAM,CAAC,CAAC;IAC3C,MAAM,CAAC,IAAI,CACT,sDAAsD,WAAW;SAC9D,GAAG,CAAC,CAAC,CAAC,EAAE,EAAE,CAAC,eAAe,CAAC,CAAC,CAAC,CAAC;SAC9B,IAAI,CAAC,IAAI,CAAC,EAAE,CAChB,CAAC;IAEF,MAAM,EAAE,GAAG,4BAA4B,EAAE,CAAC;IAC1C,MAAM,SAAS,GAAG,YAAY,EAAE,CAAC;IAEjC,MAAM,WAAW,GAAgB;QAC/B,eAAe,EAAE,WAAW;QAC5B,EAAE;QACF,UAAU,EAAE,SAAS;KACtB,CAAC;IAEF,kBAAkB;IAClB,MAAM,QAAQ,GAAG,MAAM,kBAAkB,EAAE,CAAC;IAC5C,MAAM,UAAU,CAAC,QAAQ,EAAE,WAAW,EAAE,gBAAgB,EAAE,MAAM,CAAC,CAAC;AACpE,CAAC;AAED,KAAK,UAAU,UAAU,CACvB,OAAe,EACf,MAAmB,EACnB,WAAmB,EACnB,MAAc;IAEd,MAAM,IAAI,GAAG,WAAW,CAAC;IACzB,IAAI,IAAI,GAAG,KAAK,CAAC;IACjB,IAAI,CAAC;QACH,IAAI,UAAU,GAA6B,SAAS,CAAC;QACrD,IAAI,KAAK,GAAG,CAAC,CAAC;QACd,IAAI,eAAe,GAAsB,SAAS,CAAC;QACnD,OAAO,KAAK,EAAE,GAAG,CAAC,IAAI,CAAC,UAAU,IAAI,CAAC,eAAe,EAAE,CAAC;YACtD,UAAU,GAAG,IAAA,qBAAK,EAChB,OAAO,EACP,CAAC,OAAO,EAAE,GAAG,IAAI,IAAI,IAAI,EAAE,EAAE,SAAS,EAAE,GAAG,EAAE,UAAU,EAAE,WAAW,CAAC,EACrE;gBACE,QAAQ,EAAE,IAAI;gBACd,KAAK,EAAE,CAAC,MAAM,EAAE,QAAQ,EAAE,QAAQ,CAAC;aACpC,CACF,CAAC;YACF,UAAU,CAAC,KAAK,EAAE,CAAC;YACnB,IAAI,UAAU,CAAC,GAAG,EAAE,CAAC;gBACnB,IAAI,CAAC,SAAS,CAAC,mBAAmB,EAAE,GAAG,UAAU,CAAC,GAAG,EAAE,CAAC,CAAC;YAC3D,CAAC;YACD,UAAU,CAAC,EAAE,CAAC,OAAO,EAAE,CAAC,KAAK,EAAE,EAAE;gBAC/B,eAAe,GAAG,KAAK,CAAC;YAC1B,CAAC,CAAC,CAAC;YACH,UAAU,CAAC,EAAE,CAAC,MAAM,EAAE,CAAC,IAAI,EAAE,EAAE;gBAC7B,IAAI,IAAI,KAAK,CAAC,EAAE,CAAC;oBACf,6FAA6F;oBAC7F,IAAI,GAAG,IAAI,CAAC,KAAK,CAAC,IAAI,CAAC,MAAM,EAAE,GAAG,CAAC,KAAK,GAAG,KAAK,CAAC,GAAG,KAAK,CAAC,CAAC;oBAC3D,UAAU,GAAG,SAAS,CAAC;gBACzB,CAAC;YACH,CAAC,CAAC,CAAC;YACH,UAAU,CAAC,KAAK,EAAE,KAAK,CAAC,IAAI,CAAC,SAAS,CAAC,MAAM,CAAC,CAAC,CAAC;YAChD,UAAU,CAAC,KAAK,EAAE,GAAG,EAAE,CAAC;YACxB,4CAA4C;YAC5C,MAAM,IAAI,CAAC,KAAK,CAAC,IAAI,CAAC,CAAC;QACzB,CAAC;QACD,IAAI,eAAe,EAAE,CAAC;YACpB,+DAA+D;YAC/D,MAAM,eAAe,CAAC;QACxB,CAAC;QACD,MAAM,CAAC,IAAI,CAAC,oBAAoB,IAAI,IAAI,IAAI,EAAE,CAAC,CAAC;QAChD,IAAI,CAAC,SAAS,CAAC,YAAY,EAAE,IAAI,CAAC,CAAC;QACnC,IAAI,CAAC,SAAS,CAAC,YAAY,EAAE,IAAI,CAAC,QAAQ,EAAE,CAAC,CAAC;QAC9C,IAAI,CAAC,SAAS,CAAC,sBAAsB,EAAE,MAAM,CAAC,EAAE,CAAC,IAAI,CAAC,CAAC;QAEvD,MAAM,aAAa,GAAG,MAAM,CAAC,eAAe;aACzC,MAAM,CAAC,CAAC,UAAU,EAAE,EAAE,CAAC,UAAU,CAAC,GAAG,KAAK,SAAS,CAAC;aACpD,GAAG,CAAC,CAAC,UAAU,EAAE,EAAE,CAAC,CAAC;YACpB,IAAI,EAAE,UAAU,CAAC,IAAI;YACrB,GAAG,EAAE,UAAU,CAAC,GAAG;SACpB,CAAC,CAAC,CAAC;QACN,IAAI,CAAC,SAAS,CAAC,YAAY,EAAE,IAAI,CAAC,SAAS,CAAC,aAAa,CAAC,CAAC,CAAC;IAC9D,CAAC;IAAC,OAAO,KAAK,EAAE,CAAC;QACf,IAAI,CAAC,SAAS,CAAC,8BAA8B,IAAI,CAAC,eAAe,CAAC,KAAK,CAAC,EAAE,CAAC,CAAC;IAC9E,CAAC;AACH,CAAC;AAED,kEAAkE;AAClE,+DAA+D;AAC/D,gDAAgD;AAChD,SAAS,cAAc,CAAC,MAAc;IACpC,MAAM,qBAAqB,GAAG,WAAW,CAAC,gBAAgB,CACxD,wBAAwB,CACzB,CAAC;IACF,MAAM,eAAe,GAAG,WAAW,CAAC,gBAAgB,CAAC,kBAAkB,CAAC,CAAC;IAEzE,IAAI,cAAsB,CAAC;IAC3B,IAAI,qBAAqB,KAAK,SAAS,EAAE,CAAC;QACxC,MAAM,CAAC,IAAI,CAAC,qCAAqC,CAAC,CAAC;QACnD,cAAc,GAAG,MAAM,CAAC,IAAI,CAAC,qBAAqB,EAAE,QAAQ,CAAC,CAAC,QAAQ,EAAE,CAAC;IAC3E,CAAC;SAAM,IAAI,eAAe,KAAK,SAAS,EAAE,CAAC;QACzC,MAAM,CAAC,IAAI,CAAC,+BAA+B,CAAC,CAAC;QAC7C,cAAc,GAAG,eAAe,CAAC;IACnC,CAAC;SAAM,CAAC;QACN,MAAM,CAAC,IAAI,CAAC,yBAAyB,CAAC,CAAC;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\ No newline at end of file
+{"version":3,"file":"start-proxy-action.js","sourceRoot":"","sources":["../src/start-proxy-action.ts"],"names":[],"mappings":";;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;AAAA,iDAAoD;AACpD,2CAA6B;AAE7B,oDAAsC;AACtC,+DAAiD;AACjD,2CAAiC;AAEjC,4DAA8C;AAC9C,2CAAsD;AACtD,uCAAqD;AACrD,6CAA+B;AAE/B,MAAM,eAAe,GAAG,kBAAkB,CAAC;AAC3C,MAAM,uBAAuB,GAAG,qBAAqB,CAAC;AACtD,MAAM,0BAA0B,GAC9B,kFAAkF,CAAC;AACrF,MAAM,UAAU,GAAG,YAAY,CAAC;AAChC,MAAM,QAAQ,GAAG,IAAI,CAAC;AACtB,MAAM,gBAAgB,GAAG,CAAC,CAAC;AAE3B,MAAM,yBAAyB,GAA6B;IAC1D,IAAI,EAAE,kBAAkB;IACxB,MAAM,EAAE,YAAY;IACpB,UAAU,EAAE,cAAc;IAC1B,MAAM,EAAE,cAAc;IACtB,IAAI,EAAE,iBAAiB;IACvB,IAAI,EAAE,gBAAgB;IACtB,oFAAoF;IACpF,OAAO,EAAE,EAAE;IACX,GAAG,EAAE,EAAE;IACP,EAAE,EAAE,EAAE;IACN,KAAK,EAAE,EAAE;CACD,CAAC;AA2BX,MAAM,YAAY,GAAG;IACnB;QACE,IAAI,EAAE,YAAY;QAClB,KAAK,EAAE,wBAAwB;KAChC;IACD;QACE,IAAI,EAAE,kBAAkB;QACxB,KAAK,EAAE,aAAa;KACrB;IACD;QACE,SAAS,EAAE,IAAI;QACf,KAAK,EAAE,YAAY;KACpB;IACD;QACE,IAAI,EAAE,aAAa;QACnB,KAAK,EAAE,IAAI;KACZ;IACD;QACE,SAAS,EAAE,IAAI;QACf,KAAK,EAAE,YAAY;KACpB;IACD;QACE,IAAI,EAAE,cAAc;QACpB,KAAK,EAAE,eAAe;KACvB;CACF,CAAC;AAEF,SAAS,4BAA4B;IACnC,MAAM,IAAI,GAAG,gBAAG,CAAC,GAAG,CAAC,eAAe,CAAC,QAAQ,CAAC,CAAC;IAC/C,MAAM,IAAI,GAAG,gBAAG,CAAC,iBAAiB,EAAE,CAAC;IACrC,IAAI,CAAC,SAAS,GAAG,IAAI,CAAC,SAAS,CAAC;IAChC,IAAI,CAAC,YAAY,GAAG,IAAI,CAAC;IACzB,IAAI,CAAC,QAAQ,CAAC,SAAS,GAAG,IAAI,IAAI,EAAE,CAAC;IACrC,IAAI,CAAC,QAAQ,CAAC,QAAQ,GAAG,IAAI,IAAI,EAAE,CAAC;IACpC,IAAI,CAAC,QAAQ,CAAC,QAAQ,CAAC,WAAW,CAChC,IAAI,CAAC,QAAQ,CAAC,SAAS,CAAC,WAAW,EAAE,GAAG,gBAAgB,CACzD,CAAC;IAEF,IAAI,CAAC,UAAU,CAAC,YAAY,CAAC,CAAC;IAC9B,IAAI,CAAC,SAAS,CAAC,YAAY,CAAC,CAAC;IAC7B,IAAI,CAAC,aAAa,CAAC,CAAC,EAAE,IAAI,EAAE,kBAAkB,EAAE,EAAE,EAAE,IAAI,EAAE,CAAC,CAAC,CAAC;IAC7D,IAAI,CAAC,IAAI,CAAC,IAAI,CAAC,UAAU,CAAC,CAAC;IAE3B,MAAM,GAAG,GAAG,gBAAG,CAAC,gBAAgB,CAAC,IAAI,CAAC,CAAC;IACvC,MAAM,GAAG,GAAG,gBAAG,CAAC,eAAe,CAAC,IAAI,CAAC,UAAU,CAAC,CAAC;IACjD,OAAO,EAAE,IAAI,EAAE,GAAG,EAAE,GAAG,EAAE,CAAC;AAC5B,CAAC;AAED,KAAK,UAAU,UAAU;IACvB,6CAA6C;IAC7C,WAAW,CAAC,aAAa,EAAE,CAAC;IAE5B,MAAM,MAAM,GAAG,IAAA,0BAAgB,GAAE,CAAC;IAElC,8BAA8B;IAC9B,MAAM,OAAO,GAAG,WAAW,CAAC,qBAAqB,EAAE,CAAC;IACpD,MAAM,gBAAgB,GAAG,IAAI,CAAC,OAAO,CAAC,OAAO,EAAE,WAAW,CAAC,CAAC;IAC5D,IAAI,CAAC,SAAS,CAAC,gBAAgB,EAAE,gBAAgB,CAAC,CAAC;IAEnD,gCAAgC;IAChC,MAAM,WAAW,GAAG,cAAc,CAAC,MAAM,CAAC,CAAC;IAC3C,MAAM,CAAC,IAAI,CACT,sDAAsD,WAAW;SAC9D,GAAG,CAAC,CAAC,CAAC,EAAE,EAAE,CAAC,eAAe,CAAC,CAAC,CAAC,CAAC;SAC9B,IAAI,CAAC,IAAI,CAAC,EAAE,CAChB,CAAC;IAEF,MAAM,EAAE,GAAG,4BAA4B,EAAE,CAAC;IAC1C,MAAM,SAAS,GAAG,YAAY,EAAE,CAAC;IAEjC,MAAM,WAAW,GAAgB;QAC/B,eAAe,EAAE,WAAW;QAC5B,EAAE;QACF,UAAU,EAAE,SAAS;KACtB,CAAC;IAEF,kBAAkB;IAClB,MAAM,QAAQ,GAAG,MAAM,kBAAkB,EAAE,CAAC;IAC5C,MAAM,UAAU,CAAC,QAAQ,EAAE,WAAW,EAAE,gBAAgB,EAAE,MAAM,CAAC,CAAC;AACpE,CAAC;AAED,KAAK,UAAU,UAAU,CACvB,OAAe,EACf,MAAmB,EACnB,WAAmB,EACnB,MAAc;IAEd,MAAM,IAAI,GAAG,WAAW,CAAC;IACzB,IAAI,IAAI,GAAG,KAAK,CAAC;IACjB,IAAI,CAAC;QACH,IAAI,UAAU,GAA6B,SAAS,CAAC;QACrD,IAAI,KAAK,GAAG,CAAC,CAAC;QACd,IAAI,eAAe,GAAsB,SAAS,CAAC;QACnD,OAAO,KAAK,EAAE,GAAG,CAAC,IAAI,CAAC,UAAU,IAAI,CAAC,eAAe,EAAE,CAAC;YACtD,UAAU,GAAG,IAAA,qBAAK,EAChB,OAAO,EACP,CAAC,OAAO,EAAE,GAAG,IAAI,IAAI,IAAI,EAAE,EAAE,SAAS,EAAE,GAAG,EAAE,UAAU,EAAE,WAAW,CAAC,EACrE;gBACE,QAAQ,EAAE,IAAI;gBACd,KAAK,EAAE,CAAC,MAAM,EAAE,QAAQ,EAAE,QAAQ,CAAC;aACpC,CACF,CAAC;YACF,UAAU,CAAC,KAAK,EAAE,CAAC;YACnB,IAAI,UAAU,CAAC,GAAG,EAAE,CAAC;gBACnB,IAAI,CAAC,SAAS,CAAC,mBAAmB,EAAE,GAAG,UAAU,CAAC,GAAG,EAAE,CAAC,CAAC;YAC3D,CAAC;YACD,UAAU,CAAC,EAAE,CAAC,OAAO,EAAE,CAAC,KAAK,EAAE,EAAE;gBAC/B,eAAe,GAAG,KAAK,CAAC;YAC1B,CAAC,CAAC,CAAC;YACH,UAAU,CAAC,EAAE,CAAC,MAAM,EAAE,CAAC,IAAI,EAAE,EAAE;gBAC7B,IAAI,IAAI,KAAK,CAAC,EAAE,CAAC;oBACf,6FAA6F;oBAC7F,IAAI,GAAG,IAAI,CAAC,KAAK,CAAC,IAAI,CAAC,MAAM,EAAE,GAAG,CAAC,KAAK,GAAG,KAAK,CAAC,GAAG,KAAK,CAAC,CAAC;oBAC3D,UAAU,GAAG,SAAS,CAAC;gBACzB,CAAC;YACH,CAAC,CAAC,CAAC;YACH,UAAU,CAAC,KAAK,EAAE,KAAK,CAAC,IAAI,CAAC,SAAS,CAAC,MAAM,CAAC,CAAC,CAAC;YAChD,UAAU,CAAC,KAAK,EAAE,GAAG,EAAE,CAAC;YACxB,4CAA4C;YAC5C,MAAM,IAAI,CAAC,KAAK,CAAC,IAAI,CAAC,CAAC;QACzB,CAAC;QACD,IAAI,eAAe,EAAE,CAAC;YACpB,+DAA+D;YAC/D,MAAM,eAAe,CAAC;QACxB,CAAC;QACD,MAAM,CAAC,IAAI,CAAC,oBAAoB,IAAI,IAAI,IAAI,EAAE,CAAC,CAAC;QAChD,IAAI,CAAC,SAAS,CAAC,YAAY,EAAE,IAAI,CAAC,CAAC;QACnC,IAAI,CAAC,SAAS,CAAC,YAAY,EAAE,IAAI,CAAC,QAAQ,EAAE,CAAC,CAAC;QAC9C,IAAI,CAAC,SAAS,CAAC,sBAAsB,EAAE,MAAM,CAAC,EAAE,CAAC,IAAI,CAAC,CAAC;QAEvD,MAAM,aAAa,GAAG,MAAM,CAAC,eAAe;aACzC,MAAM,CAAC,CAAC,UAAU,EAAE,EAAE,CAAC,UAAU,CAAC,GAAG,KAAK,SAAS,CAAC;aACpD,GAAG,CAAC,CAAC,UAAU,EAAE,EAAE,CAAC,CAAC;YACpB,IAAI,EAAE,UAAU,CAAC,IAAI;YACrB,GAAG,EAAE,UAAU,CAAC,GAAG;SACpB,CAAC,CAAC,CAAC;QACN,IAAI,CAAC,SAAS,CAAC,YAAY,EAAE,IAAI,CAAC,SAAS,CAAC,aAAa,CAAC,CAAC,CAAC;IAC9D,CAAC;IAAC,OAAO,KAAK,EAAE,CAAC;QACf,IAAI,CAAC,SAAS,CAAC,8BAA8B,IAAI,CAAC,eAAe,CAAC,KAAK,CAAC,EAAE,CAAC,CAAC;IAC9E,CAAC;AACH,CAAC;AAED,kEAAkE;AAClE,+DAA+D;AAC/D,gDAAgD;AAChD,SAAS,cAAc,CAAC,MAAc;IACpC,MAAM,qBAAqB,GAAG,WAAW,CAAC,gBAAgB,CACxD,wBAAwB,CACzB,CAAC;IACF,MAAM,eAAe,GAAG,WAAW,CAAC,gBAAgB,CAAC,kBAAkB,CAAC,CAAC;IACzE,MAAM,cAAc,GAAG,WAAW,CAAC,gBAAgB,CAAC,UAAU,CAAC,CAAC;IAChE,MAAM,QAAQ,GAAG,cAAc,CAA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\ No newline at end of file
diff --git a/src/languages.ts b/src/languages.ts
index e2ac61455c..e25e87fa5b 100644
--- a/src/languages.ts
+++ b/src/languages.ts
@@ -19,6 +19,8 @@ export const LANGUAGE_ALIASES: { [lang: string]: Language } = {
   "c#": Language.csharp,
   kotlin: Language.java,
   typescript: Language.javascript,
+  "javascript-typescript": Language.javascript,
+  "java-kotlin": Language.java,
 };
 
 /**
diff --git a/src/start-proxy-action.ts b/src/start-proxy-action.ts
index c7b272841d..0cbfcf7173 100644
--- a/src/start-proxy-action.ts
+++ b/src/start-proxy-action.ts
@@ -6,6 +6,7 @@ import * as toolcache from "@actions/tool-cache";
 import { pki } from "node-forge";
 
 import * as actionsUtil from "./actions-util";
+import { Language, parseLanguage } from "./languages";
 import { getActionsLogger, Logger } from "./logging";
 import * as util from "./util";
 
@@ -17,6 +18,20 @@ const PROXY_USER = "proxy_user";
 const KEY_SIZE = 2048;
 const KEY_EXPIRY_YEARS = 2;
 
+const LANGUAGE_TO_REGISTRY_TYPE: Record<Language, string> = {
+  java: "maven_repository",
+  csharp: "nuget_feed",
+  javascript: "npm_registry",
+  python: "python_index",
+  ruby: "rubygems_server",
+  rust: "cargo_registry",
+  // We do not have an established proxy type for these languages, thus leaving empty.
+  actions: "",
+  cpp: "",
+  go: "",
+  swift: "",
+} as const;
+
 type CertificateAuthority = {
   cert: string;
   key: string;
@@ -192,6 +207,11 @@ function getCredentials(logger: Logger): Credential[] {
     "registries_credentials",
   );
   const registrySecrets = actionsUtil.getOptionalInput("registry_secrets");
+  const languageString = actionsUtil.getOptionalInput("language");
+  const language = languageString ? parseLanguage(languageString) : undefined;
+  const registryTypeForLanguage = language
+    ? LANGUAGE_TO_REGISTRY_TYPE[language]
+    : undefined;
 
   let credentialsStr: string;
   if (registriesCredentials !== undefined) {
@@ -212,6 +232,13 @@ function getCredentials(logger: Logger): Credential[] {
     if (e.url === undefined && e.host === undefined) {
       throw new Error("Invalid credentials - must specify host or url");
     }
+
+    // Filter credentials based on language if specified. `type` is the registry type.
+    // E.g., "maven_feed" for Java/Kotlin, "nuget_repository" for C#.
+    if (e.type !== registryTypeForLanguage) {
+      continue;
+    }
+
     out.push({
       type: e.type,
       host: e.host,
diff --git a/start-proxy/action.yml b/start-proxy/action.yml
index 2bcce1d9e6..cf52125dd7 100644
--- a/start-proxy/action.yml
+++ b/start-proxy/action.yml
@@ -16,6 +16,9 @@ inputs:
     description: GitHub token to use for authenticating with this instance of GitHub, used to upload debug artifacts.
     default: ${{ github.token }}
     required: false
+  language:
+    description: The programming language to setup the proxy for the correct ecosystem
+    required: false
 outputs:
   proxy_host:
     description: The IP address of the proxy