diff --git a/Jakefile.js b/Jakefile.js
index 807546d59f8..8cf6c9f5953 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -129,6 +129,7 @@ var harnessSources = harnessCoreSources.concat([
     "initializeTSConfig.ts",
     "printer.ts",
     "textChanges.ts",
+    "telemetry.ts",
     "transform.ts",
     "customTransforms.ts",
 ].map(function (f) {
diff --git a/package.json b/package.json
index 689c769a870..52531aa024b 100644
--- a/package.json
+++ b/package.json
@@ -76,7 +76,7 @@
         "travis-fold": "latest",
         "ts-node": "latest",
         "tslint": "next",
-        "typescript": "next"
+        "typescript": "^2.3.3"
     },
     "scripts": {
         "pretest": "jake tests",
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index a5990a5a31b..347d632bef4 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -691,8 +691,7 @@ namespace ts {
         return typeAcquisition;
     }
 
-    /* @internal */
-    export function getOptionNameMap(): OptionNameMap {
+    function getOptionNameMap(): OptionNameMap {
         if (optionNameMapCache) {
             return optionNameMapCache;
         }
@@ -745,7 +744,6 @@ namespace ts {
         const options: CompilerOptions = {};
         const fileNames: string[] = [];
         const errors: Diagnostic[] = [];
-        const { optionNameMap, shortOptionNames } = getOptionNameMap();
 
         parseStrings(commandLine);
         return {
@@ -757,21 +755,13 @@ namespace ts {
         function parseStrings(args: string[]) {
             let i = 0;
             while (i < args.length) {
-                let s = args[i];
+                const s = args[i];
                 i++;
                 if (s.charCodeAt(0) === CharacterCodes.at) {
                     parseResponseFile(s.slice(1));
                 }
                 else if (s.charCodeAt(0) === CharacterCodes.minus) {
-                    s = s.slice(s.charCodeAt(1) === CharacterCodes.minus ? 2 : 1).toLowerCase();
-
-                    // Try to translate short option names to their full equivalents.
-                    const short = shortOptionNames.get(s);
-                    if (short !== undefined) {
-                        s = short;
-                    }
-
-                    const opt = optionNameMap.get(s);
+                    const opt = getOptionFromName(s.slice(s.charCodeAt(1) === CharacterCodes.minus ? 2 : 1), /*allowShort*/ true);
                     if (opt) {
                         if (opt.isTSConfigOnly) {
                             errors.push(createCompilerDiagnostic(Diagnostics.Option_0_can_only_be_specified_in_tsconfig_json_file, opt.name));
@@ -859,6 +849,19 @@ namespace ts {
         }
     }
 
+    function getOptionFromName(optionName: string, allowShort = false): CommandLineOption | undefined {
+        optionName = optionName.toLowerCase();
+        const { optionNameMap, shortOptionNames } = getOptionNameMap();
+        // Try to translate short option names to their full equivalents.
+        if (allowShort) {
+            const short = shortOptionNames.get(optionName);
+            if (short !== undefined) {
+                optionName = short;
+            }
+        }
+        return optionNameMap.get(optionName);
+    }
+
     /**
      * Read tsconfig.json file
      * @param fileName The path to the config file
@@ -1661,4 +1664,42 @@ namespace ts {
     function caseInsensitiveKeyMapper(key: string) {
         return key.toLowerCase();
     }
-}
\ No newline at end of file
+
+    /**
+     * Produces a cleaned version of compiler options with personally identifiying info (aka, paths) removed.
+     * Also converts enum values back to strings.
+     */
+    /* @internal */
+    export function convertCompilerOptionsForTelemetry(opts: ts.CompilerOptions): ts.CompilerOptions {
+        const out: ts.CompilerOptions = {};
+        for (const key in opts) if (opts.hasOwnProperty(key)) {
+            const type = getOptionFromName(key);
+            if (type !== undefined) { // Ignore unknown options
+                out[key] = getOptionValueWithEmptyStrings(opts[key], type);
+            }
+        }
+        return out;
+    }
+
+    function getOptionValueWithEmptyStrings(value: any, option: CommandLineOption): {} {
+        switch (option.type) {
+            case "object": // "paths". Can't get any useful information from the value since we blank out strings, so just return "".
+                return "";
+            case "string": // Could be any arbitrary string -- use empty string instead.
+                return "";
+            case "number": // Allow numbers, but be sure to check it's actually a number.
+                return typeof value === "number" ? value : "";
+            case "boolean":
+                return typeof value === "boolean" ? value : "";
+            case "list":
+                const elementType = (option as CommandLineOptionOfListType).element;
+                return ts.isArray(value) ? value.map(v => getOptionValueWithEmptyStrings(v, elementType)) : "";
+            default:
+                return ts.forEachEntry(option.type, (optionEnumValue, optionStringValue) => {
+                    if (optionEnumValue === value) {
+                        return optionStringValue;
+                    }
+                });
+        }
+    }
+}
diff --git a/src/harness/tsconfig.json b/src/harness/tsconfig.json
index d752c0f235b..6553f3667a7 100644
--- a/src/harness/tsconfig.json
+++ b/src/harness/tsconfig.json
@@ -127,6 +127,7 @@
         "./unittests/printer.ts",
         "./unittests/transform.ts",
         "./unittests/customTransforms.ts",
-        "./unittests/textChanges.ts"
+        "./unittests/textChanges.ts",
+        "./unittests/telemetry.ts"
     ]
 }
diff --git a/src/harness/unittests/telemetry.ts b/src/harness/unittests/telemetry.ts
new file mode 100644
index 00000000000..d3811edf251
--- /dev/null
+++ b/src/harness/unittests/telemetry.ts
@@ -0,0 +1,291 @@
+/// <reference path="../harness.ts" />
+/// <reference path="./tsserverProjectSystem.ts" />
+
+namespace ts.projectSystem {
+    describe("project telemetry", () => {
+        it("does nothing for inferred project", () => {
+            const file = makeFile("/a.js");
+            const et = new EventTracker([file]);
+            et.service.openClientFile(file.path);
+            assert.equal(et.getEvents().length, 0);
+        });
+        it("only sends an event once", () => {
+            const file = makeFile("/a.ts");
+            const tsconfig = makeFile("/tsconfig.json", {});
+
+            const et = new EventTracker([file, tsconfig]);
+            et.service.openClientFile(file.path);
+            et.assertProjectInfoTelemetryEvent({});
+
+            et.service.closeClientFile(file.path);
+            checkNumberOfProjects(et.service, { configuredProjects: 0 });
+
+            et.service.openClientFile(file.path);
+            checkNumberOfProjects(et.service, { configuredProjects: 1 });
+
+            assert.equal(et.getEvents().length, 0);
+        });
+
+        it("counts files by extension", () => {
+            const files = ["ts.ts", "tsx.tsx", "moo.ts", "dts.d.ts", "jsx.jsx", "js.js", "badExtension.badExtension"].map(f => makeFile(`/src/${f}`));
+            const notIncludedFile = makeFile("/bin/ts.js");
+            const compilerOptions: ts.CompilerOptions = { allowJs: true };
+            const tsconfig = makeFile("/tsconfig.json", { compilerOptions, include: ["src"] });
+
+            const et = new EventTracker([...files, notIncludedFile, tsconfig]);
+            et.service.openClientFile(files[0].path);
+            et.assertProjectInfoTelemetryEvent({
+                fileStats: { ts: 2, tsx: 1, js: 1, jsx: 1, dts: 1 },
+                compilerOptions,
+                include: true,
+            });
+        });
+
+        it("works with external project", () => {
+            const file1 = makeFile("/a.ts");
+            const et = new EventTracker([file1]);
+            const compilerOptions: ts.CompilerOptions = { strict: true };
+
+            const projectFileName = "foo.csproj";
+
+            open();
+
+            // TODO: Apparently compilerOptions is mutated, so have to repeat it here!
+            et.assertProjectInfoTelemetryEvent({
+                compilerOptions: { strict: true },
+                compileOnSave: true,
+                // These properties can't be present for an external project, so they are undefined instead of false.
+                extends: undefined,
+                files: undefined,
+                include: undefined,
+                exclude: undefined,
+                configFileName: "other",
+                projectType: "external",
+            });
+
+            // Also test that opening an external project only sends an event once.
+
+            et.service.closeExternalProject(projectFileName);
+            checkNumberOfProjects(et.service, { externalProjects: 0 });
+
+            open();
+            assert.equal(et.getEvents().length, 0);
+
+            function open(): void {
+                et.service.openExternalProject({
+                    rootFiles: toExternalFiles([file1.path]),
+                    options: compilerOptions,
+                    projectFileName: projectFileName,
+                });
+                checkNumberOfProjects(et.service, { externalProjects: 1 });
+            }
+        });
+
+        it("does not expose paths", () => {
+            const file = makeFile("/a.ts");
+
+            const compilerOptions: ts.CompilerOptions = {
+                project: "",
+                outFile: "hunter2.js",
+                outDir: "hunter2",
+                rootDir: "hunter2",
+                baseUrl: "hunter2",
+                rootDirs: ["hunter2"],
+                typeRoots: ["hunter2"],
+                types: ["hunter2"],
+                sourceRoot: "hunter2",
+                mapRoot: "hunter2",
+                jsxFactory: "hunter2",
+                out: "hunter2",
+                reactNamespace: "hunter2",
+                charset: "hunter2",
+                locale: "hunter2",
+                declarationDir: "hunter2",
+                paths: {
+                    "*": ["hunter2"],
+                },
+
+                // Boolean / number options get through
+                declaration: true,
+
+                // List of string enum gets through -- but only if legitimately a member of the enum
+                lib: ["es6", "dom", "hunter2"],
+
+                // Sensitive data doesn't get through even if sent to an option of safe type
+                checkJs: "hunter2" as any as boolean,
+            };
+            const safeCompilerOptions: ts.CompilerOptions = {
+                project: "",
+                outFile: "",
+                outDir: "",
+                rootDir: "",
+                baseUrl: "",
+                rootDirs: [""],
+                typeRoots: [""],
+                types: [""],
+                sourceRoot: "",
+                mapRoot: "",
+                jsxFactory: "",
+                out: "",
+                reactNamespace: "",
+                charset: "",
+                locale: "",
+                declarationDir: "",
+                paths: "" as any,
+
+                declaration: true,
+
+                lib: ["es6", "dom"],
+
+                checkJs: "" as any as boolean,
+            };
+            (compilerOptions as any).unknownCompilerOption = "hunter2"; // These are always ignored.
+            const tsconfig = makeFile("/tsconfig.json", { compilerOptions, files: ["/a.ts"] });
+
+            const et = new EventTracker([file, tsconfig]);
+            et.service.openClientFile(file.path);
+
+            et.assertProjectInfoTelemetryEvent({
+                compilerOptions: safeCompilerOptions,
+                files: true,
+            });
+        });
+
+        it("sends telemetry for extends, files, include, exclude, and compileOnSave", () => {
+            const file = makeFile("/hunter2/a.ts");
+            const tsconfig = makeFile("/tsconfig.json", {
+                compilerOptions: {},
+                extends: "hunter2.json",
+                files: ["hunter2/a.ts"],
+                include: ["hunter2"],
+                exclude: ["hunter2"],
+                compileOnSave: true,
+            });
+
+            const et = new EventTracker([tsconfig, file]);
+            et.service.openClientFile(file.path);
+            et.assertProjectInfoTelemetryEvent({
+                extends: true,
+                files: true,
+                include: true,
+                exclude: true,
+                compileOnSave: true,
+            });
+        });
+
+        const autoJsCompilerOptions = {
+            // Apparently some options are added by default.
+            allowJs: true,
+            allowSyntheticDefaultImports: true,
+            maxNodeModuleJsDepth: 2,
+            skipLibCheck: true,
+        };
+
+        it("sends telemetry for typeAcquisition settings", () => {
+            const file = makeFile("/a.js");
+            const jsconfig = makeFile("/jsconfig.json", {
+                compilerOptions: {},
+                typeAcquisition: {
+                    enable: true,
+                    enableAutoDiscovery: false,
+                    include: ["hunter2", "hunter3"],
+                    exclude: [],
+                },
+            });
+            const et = new EventTracker([jsconfig, file]);
+            et.service.openClientFile(file.path);
+            et.assertProjectInfoTelemetryEvent({
+                fileStats: fileStats({ js: 1 }),
+                compilerOptions: autoJsCompilerOptions,
+                typeAcquisition: {
+                    enable: true,
+                    include: true,
+                    exclude: false,
+                },
+                configFileName: "jsconfig.json",
+            });
+        });
+
+        it("detects whether language service was disabled", () => {
+            const file = makeFile("/a.js");
+            const tsconfig = makeFile("/jsconfig.json", {});
+            const et = new EventTracker([tsconfig, file]);
+            et.host.getFileSize = () => server.maxProgramSizeForNonTsFiles + 1;
+            et.service.openClientFile(file.path);
+            et.getEvent<server.ProjectLanguageServiceStateEvent>(server.ProjectLanguageServiceStateEvent, /*mayBeMore*/ true);
+            et.assertProjectInfoTelemetryEvent({
+                fileStats: fileStats({ js: 1 }),
+                compilerOptions: autoJsCompilerOptions,
+                configFileName: "jsconfig.json",
+                typeAcquisition: {
+                    enable: true,
+                    include: false,
+                    exclude: false,
+                },
+                languageServiceEnabled: false,
+            });
+        });
+    });
+
+    class EventTracker {
+        private events: server.ProjectServiceEvent[] = [];
+        readonly service: TestProjectService;
+        readonly host: projectSystem.TestServerHost;
+
+        constructor(files: projectSystem.FileOrFolder[]) {
+            this.host = createServerHost(files);
+            this.service = createProjectService(this.host, {
+                eventHandler: event => {
+                    this.events.push(event);
+                },
+            });
+        }
+
+        getEvents(): ReadonlyArray<server.ProjectServiceEvent> {
+            const events = this.events;
+            this.events = [];
+            return events;
+        }
+
+        assertProjectInfoTelemetryEvent(partial: Partial<server.ProjectInfoTelemetryEventData>): void {
+            assert.deepEqual(this.getEvent<server.ProjectInfoTelemetryEvent>(ts.server.ProjectInfoTelemetryEvent), makePayload(partial));
+        }
+
+        getEvent<T extends server.ProjectServiceEvent>(eventName: T["eventName"], mayBeMore = false): T["data"] {
+            if (mayBeMore) assert(this.events.length !== 0); else assert.equal(this.events.length, 1);
+            const event = this.events.shift();
+            assert.equal(event.eventName, eventName);
+            return event.data;
+        }
+    }
+
+    function makePayload(partial: Partial<server.ProjectInfoTelemetryEventData>): server.ProjectInfoTelemetryEventData {
+        return {
+            fileStats: fileStats({ ts: 1 }),
+            compilerOptions: {},
+            extends: false,
+            files: false,
+            include: false,
+            exclude: false,
+            compileOnSave: false,
+            typeAcquisition: {
+                enable: false,
+                exclude: false,
+                include: false,
+            },
+            configFileName: "tsconfig.json",
+            projectType: "configured",
+            languageServiceEnabled: true,
+            version: ts.version,
+            ...partial
+        };
+    }
+
+    function makeFile(path: string, content: {} = ""): projectSystem.FileOrFolder {
+        return { path, content: typeof content === "string" ? "" : JSON.stringify(content) };
+    }
+
+    function fileStats(nonZeroStats: Partial<server.FileStats>): server.FileStats {
+        return { ts: 0, tsx: 0, dts: 0, js: 0, jsx: 0, ...nonZeroStats };
+    }
+}
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 33838b5805f..57ce680faf1 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -2230,7 +2230,7 @@ namespace ts.projectSystem {
 
             let lastEvent: server.ProjectLanguageServiceStateEvent;
             const session = createSession(host, /*typingsInstaller*/ undefined, e => {
-                if (e.eventName === server.ConfigFileDiagEvent || e.eventName === server.ContextEvent) {
+                if (e.eventName === server.ConfigFileDiagEvent || e.eventName === server.ContextEvent || e.eventName === server.ProjectInfoTelemetryEvent) {
                     return;
                 }
                 assert.equal(e.eventName, server.ProjectLanguageServiceStateEvent);
@@ -2280,7 +2280,7 @@ namespace ts.projectSystem {
                 filePath === f2.path ? server.maxProgramSizeForNonTsFiles + 1 : originalGetFileSize.call(host, filePath);
             let lastEvent: server.ProjectLanguageServiceStateEvent;
             const session = createSession(host, /*typingsInstaller*/ undefined, e => {
-                if (e.eventName === server.ConfigFileDiagEvent) {
+                if (e.eventName === server.ConfigFileDiagEvent || e.eventName === server.ProjectInfoTelemetryEvent) {
                     return;
                 }
                 assert.equal(e.eventName, server.ProjectLanguageServiceStateEvent);
diff --git a/src/harness/unittests/typingsInstaller.ts b/src/harness/unittests/typingsInstaller.ts
index af95874a32c..699b1807428 100644
--- a/src/harness/unittests/typingsInstaller.ts
+++ b/src/harness/unittests/typingsInstaller.ts
@@ -44,7 +44,7 @@ namespace ts.projectSystem {
         });
     }
 
-    import typingsName = server.typingsInstaller.typingsName;
+    import typingsName = TI.typingsName;
 
     describe("local module", () => {
         it("should not be picked up", () => {
@@ -73,7 +73,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { typesRegistry: createTypesRegistry("config"), globalTypingsCacheLocation: typesCache });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, _cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, _cb: TI.RequestCompletedAction) {
                     assert(false, "should not be called");
                 }
             })();
@@ -121,7 +121,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { typesRegistry: createTypesRegistry("jquery") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/jquery"];
                     const typingFiles = [jquery];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -165,7 +165,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { typesRegistry: createTypesRegistry("jquery") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/jquery"];
                     const typingFiles = [jquery];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -672,7 +672,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: "/tmp", typesRegistry: createTypesRegistry("jquery") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/jquery"];
                     const typingFiles = [jqueryDTS];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -718,7 +718,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: "/tmp", typesRegistry: createTypesRegistry("jquery") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/jquery"];
                     const typingFiles = [jqueryDTS];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -765,7 +765,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: "/tmp", typesRegistry: createTypesRegistry("jquery") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/jquery"];
                     const typingFiles = [jqueryDTS];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -808,7 +808,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: cachePath, typesRegistry: createTypesRegistry("commander") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/commander"];
                     const typingFiles = [commander];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -849,7 +849,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: cachePath, typesRegistry: createTypesRegistry("node", "commander") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/node", "@types/commander"];
                     const typingFiles = [node, commander];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -888,7 +888,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: "/tmp", typesRegistry: createTypesRegistry("foo") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     executeCommand(this, host, ["foo"], [], cb);
                 }
             })();
@@ -996,7 +996,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: "/tmp" }, { isEnabled: () => true, writeLine: msg => messages.push(msg) });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, _cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, _cb: TI.RequestCompletedAction) {
                     assert(false, "runCommand should not be invoked");
                 }
             })();
@@ -1060,7 +1060,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: cachePath, typesRegistry: createTypesRegistry("commander") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/commander"];
                     const typingFiles = [commander];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -1110,7 +1110,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: cachePath, typesRegistry: createTypesRegistry("commander") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     const installedTypings = ["@types/commander"];
                     const typingFiles = [commander];
                     executeCommand(this, host, installedTypings, typingFiles, cb);
@@ -1157,7 +1157,7 @@ namespace ts.projectSystem {
                 constructor() {
                     super(host, { globalTypingsCacheLocation: cachePath, typesRegistry: createTypesRegistry("commander") });
                 }
-                installWorker(_requestId: number, _args: string[], _cwd: string, cb: server.typingsInstaller.RequestCompletedAction) {
+                installWorker(_requestId: number, _args: string[], _cwd: string, cb: TI.RequestCompletedAction) {
                     executeCommand(this, host, "", [], cb);
                 }
                 sendResponse(response: server.SetTypings | server.InvalidateCachedTypings | server.BeginInstallTypes | server.EndInstallTypes) {
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index d8322f5e7c5..7c0e0a0fb92 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -13,6 +13,7 @@ namespace ts.server {
     export const ContextEvent = "context";
     export const ConfigFileDiagEvent = "configFileDiag";
     export const ProjectLanguageServiceStateEvent = "projectLanguageServiceState";
+    export const ProjectInfoTelemetryEvent = "projectInfo";
 
     export interface ContextEvent {
         eventName: typeof ContextEvent;
@@ -29,7 +30,52 @@ namespace ts.server {
         data: { project: Project, languageServiceEnabled: boolean };
     }
 
-    export type ProjectServiceEvent = ContextEvent | ConfigFileDiagEvent | ProjectLanguageServiceStateEvent;
+    /** This will be converted to the payload of a protocol.TelemetryEvent in session.defaultEventHandler. */
+    export interface ProjectInfoTelemetryEvent {
+        readonly eventName: typeof ProjectInfoTelemetryEvent;
+        readonly data: ProjectInfoTelemetryEventData;
+    }
+
+    export interface ProjectInfoTelemetryEventData {
+        /** Count of file extensions seen in the project. */
+        readonly fileStats: FileStats;
+        /**
+         * Any compiler options that might contain paths will be taken out.
+         * Enum compiler options will be converted to strings.
+         */
+        readonly compilerOptions: ts.CompilerOptions;
+        // "extends", "files", "include", or "exclude" will be undefined if an external config is used.
+        // Otherwise, we will use "true" if the property is present and "false" if it is missing.
+        readonly extends: boolean | undefined;
+        readonly files: boolean | undefined;
+        readonly include: boolean | undefined;
+        readonly exclude: boolean | undefined;
+        readonly compileOnSave: boolean;
+        readonly typeAcquisition: ProjectInfoTypeAcquisitionData;
+
+        readonly configFileName: "tsconfig.json" | "jsconfig.json" | "other";
+        readonly projectType: "external" | "configured";
+        readonly languageServiceEnabled: boolean;
+        /** TypeScript version used by the server. */
+        readonly version: string;
+    }
+
+    export interface ProjectInfoTypeAcquisitionData {
+        readonly enable: boolean;
+        // Actual values of include/exclude entries are scrubbed.
+        readonly include: boolean;
+        readonly exclude: boolean;
+    }
+
+    export interface FileStats {
+        readonly js: number;
+        readonly jsx: number;
+        readonly ts: number;
+        readonly tsx: number;
+        readonly dts: number;
+    }
+
+    export type ProjectServiceEvent = ContextEvent | ConfigFileDiagEvent | ProjectLanguageServiceStateEvent | ProjectInfoTelemetryEvent;
 
     export interface ProjectServiceEventHandler {
         (event: ProjectServiceEvent): void;
@@ -345,6 +391,9 @@ namespace ts.server {
         public readonly pluginProbeLocations: ReadonlyArray<string>;
         public readonly allowLocalPluginLoads: boolean;
 
+        /** Tracks projects that we have already sent telemetry for. */
+        private readonly seenProjects = createMap<true>();
+
         constructor(opts: ProjectServiceOptions) {
             this.host = opts.host;
             this.logger = opts.logger;
@@ -934,7 +983,10 @@ namespace ts.server {
             const projectOptions: ProjectOptions = {
                 files: parsedCommandLine.fileNames,
                 compilerOptions: parsedCommandLine.options,
-                configHasFilesProperty: config["files"] !== undefined,
+                configHasExtendsProperty: config.extends !== undefined,
+                configHasFilesProperty: config.files !== undefined,
+                configHasIncludeProperty: config.include !== undefined,
+                configHasExcludeProperty: config.exclude !== undefined,
                 wildcardDirectories: createMapFromTemplate(parsedCommandLine.wildcardDirectories),
                 typeAcquisition: parsedCommandLine.typeAcquisition,
                 compileOnSave: parsedCommandLine.compileOnSave
@@ -984,9 +1036,53 @@ namespace ts.server {
 
             this.addFilesToProjectAndUpdateGraph(project, files, externalFilePropertyReader, /*clientFileName*/ undefined, typeAcquisition, /*configFileErrors*/ undefined);
             this.externalProjects.push(project);
+            this.sendProjectTelemetry(project.externalProjectName, project);
             return project;
         }
 
+        private sendProjectTelemetry(projectKey: string, project: server.ExternalProject | server.ConfiguredProject, projectOptions?: ProjectOptions): void {
+            if (this.seenProjects.has(projectKey)) {
+                return;
+            }
+            this.seenProjects.set(projectKey, true);
+
+            if (!this.eventHandler) return;
+
+            const data: ProjectInfoTelemetryEventData = {
+                fileStats: countEachFileTypes(project.getScriptInfos()),
+                compilerOptions: convertCompilerOptionsForTelemetry(project.getCompilerOptions()),
+                typeAcquisition: convertTypeAcquisition(project.getTypeAcquisition()),
+                extends: projectOptions && projectOptions.configHasExtendsProperty,
+                files: projectOptions && projectOptions.configHasFilesProperty,
+                include: projectOptions && projectOptions.configHasIncludeProperty,
+                exclude: projectOptions && projectOptions.configHasExcludeProperty,
+                compileOnSave: project.compileOnSaveEnabled,
+                configFileName: configFileName(),
+                projectType: project instanceof server.ExternalProject ? "external" : "configured",
+                languageServiceEnabled: project.languageServiceEnabled,
+                version: ts.version,
+            };
+            this.eventHandler({ eventName: ProjectInfoTelemetryEvent, data });
+
+            function configFileName(): ProjectInfoTelemetryEventData["configFileName"] {
+                if (!(project instanceof server.ConfiguredProject)) {
+                    return "other";
+                }
+
+                const configFilePath = project instanceof server.ConfiguredProject && project.getConfigFilePath();
+                const base = ts.getBaseFileName(configFilePath);
+                return base === "tsconfig.json" || base === "jsconfig.json" ? base : "other";
+            }
+
+            function convertTypeAcquisition({ enable, include, exclude }: TypeAcquisition): ProjectInfoTypeAcquisitionData {
+                return {
+                    enable,
+                    include: include !== undefined && include.length !== 0,
+                    exclude: exclude !== undefined && exclude.length !== 0,
+                };
+            }
+        }
+
         private reportConfigFileDiagnostics(configFileName: string, diagnostics: Diagnostic[], triggerFile: string) {
             if (!this.eventHandler) {
                 return;
@@ -1020,6 +1116,7 @@ namespace ts.server {
             project.watchTypeRoots((project, path) => this.onTypeRootFileChanged(project, path));
 
             this.configuredProjects.push(project);
+            this.sendProjectTelemetry(project.getConfigFilePath(), project, projectOptions);
             return project;
         }
 
@@ -1052,7 +1149,7 @@ namespace ts.server {
             const conversionResult = this.convertConfigFileContentToProjectOptions(configFileName);
             const projectOptions: ProjectOptions = conversionResult.success
                 ? conversionResult.projectOptions
-                : { files: [], compilerOptions: {}, typeAcquisition: { enable: false } };
+                : { files: [], compilerOptions: {}, configHasExtendsProperty: false, configHasFilesProperty: false, configHasIncludeProperty: false, configHasExcludeProperty: false, typeAcquisition: { enable: false } };
             const project = this.createAndAddConfiguredProject(configFileName, projectOptions, conversionResult.configFileErrors, clientFileName);
             return {
                 success: conversionResult.success,
diff --git a/src/server/project.ts b/src/server/project.ts
index 6aded117599..ac56a6e3b98 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -20,7 +20,7 @@ namespace ts.server {
         }
     }
 
-    function countEachFileTypes(infos: ScriptInfo[]): { js: number, jsx: number, ts: number, tsx: number, dts: number } {
+    export function countEachFileTypes(infos: ScriptInfo[]): FileStats {
         const result = { js: 0, jsx: 0, ts: 0, tsx: 0, dts: 0 };
         for (const info of infos) {
             switch (info.scriptKind) {
@@ -737,6 +737,10 @@ namespace ts.server {
         }
     }
 
+    /**
+     * If a file is opened and no tsconfig (or jsconfig) is found,
+     * the file and its imports/references are put into an InferredProject.
+     */
     export class InferredProject extends Project {
 
         private static newName = (() => {
@@ -830,6 +834,11 @@ namespace ts.server {
         }
     }
 
+    /**
+     * If a file is opened, the server will look for a tsconfig (or jsconfig)
+     * and if successfull create a ConfiguredProject for it.
+     * Otherwise it will create an InferredProject.
+     */
     export class ConfiguredProject extends Project {
         private typeAcquisition: TypeAcquisition;
         private projectFileWatcher: FileWatcher;
@@ -1055,6 +1064,10 @@ namespace ts.server {
         }
     }
 
+    /**
+     * Project whose configuration is handled externally, such as in a '.csproj'.
+     * These are created only if a host explicitly calls `openExternalProject`.
+     */
     export class ExternalProject extends Project {
         private typeAcquisition: TypeAcquisition;
         constructor(public externalProjectName: string,
diff --git a/src/server/session.ts b/src/server/session.ts
index cee9698d6d9..96aaefbcdda 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -464,13 +464,22 @@ namespace ts.server {
                     const { triggerFile, configFileName, diagnostics } = event.data;
                     this.configFileDiagnosticEvent(triggerFile, configFileName, diagnostics);
                     break;
-                case ProjectLanguageServiceStateEvent:
+                case ProjectLanguageServiceStateEvent: {
                     const eventName: protocol.ProjectLanguageServiceStateEventName = "projectLanguageServiceState";
                     this.event(<protocol.ProjectLanguageServiceStateEventBody>{
                         projectName: event.data.project.getProjectName(),
                         languageServiceEnabled: event.data.languageServiceEnabled
                     }, eventName);
                     break;
+                }
+                case ProjectInfoTelemetryEvent: {
+                    const eventName: protocol.TelemetryEventName = "telemetry";
+                    this.event(<protocol.TelemetryEventBody>{
+                        telemetryEventName: event.eventName,
+                        payload: event.data,
+                    }, eventName);
+                    break;
+                }
             }
         }
 
diff --git a/src/server/utilities.ts b/src/server/utilities.ts
index ffc09f29ccd..093958b60c5 100644
--- a/src/server/utilities.ts
+++ b/src/server/utilities.ts
@@ -164,10 +164,13 @@ namespace ts.server {
     }
 
     export interface ProjectOptions {
+        configHasExtendsProperty: boolean;
         /**
          * true if config file explicitly listed files
          */
-        configHasFilesProperty?: boolean;
+        configHasFilesProperty: boolean;
+        configHasIncludeProperty: boolean;
+        configHasExcludeProperty: boolean;
         /**
          * these fields can be present in the project file
          */