diff --git a/packages/language-server/src/lib/documents/DocumentManager.ts b/packages/language-server/src/lib/documents/DocumentManager.ts
index db421b44f..c30387be1 100644
--- a/packages/language-server/src/lib/documents/DocumentManager.ts
+++ b/packages/language-server/src/lib/documents/DocumentManager.ts
@@ -18,9 +18,11 @@ export class DocumentManager {
     public locked = new Set<string>();
     public deleteCandidates = new Set<string>();
 
-    constructor(private createDocument: (textDocument: TextDocumentItem) => Document) {}
+    constructor(
+        private createDocument: (textDocument: Pick<TextDocumentItem, 'text' | 'uri'>) => Document,
+    ) {}
 
-    openDocument(textDocument: TextDocumentItem): Document {
+    openDocument(textDocument: Pick<TextDocumentItem, 'text' | 'uri'>): Document {
         let document: Document;
         if (this.documents.has(textDocument.uri)) {
             document = this.documents.get(textDocument.uri)!;
@@ -45,8 +47,9 @@ export class DocumentManager {
     }
 
     getAllOpenedByClient() {
-        return Array.from(this.documents.entries())
-            .filter((doc) => this.openedInClient.has(doc[0]));
+        return Array.from(this.documents.entries()).filter((doc) =>
+            this.openedInClient.has(doc[0]),
+        );
     }
 
     releaseDocument(uri: string): void {
@@ -58,7 +61,6 @@ export class DocumentManager {
         }
     }
 
-
     closeDocument(uri: string) {
         const document = this.documents.get(uri);
         if (!document) {
diff --git a/packages/language-server/src/plugins/typescript/LSAndTSDocResolver.ts b/packages/language-server/src/plugins/typescript/LSAndTSDocResolver.ts
index eee4f5fef..599c83216 100644
--- a/packages/language-server/src/plugins/typescript/LSAndTSDocResolver.ts
+++ b/packages/language-server/src/plugins/typescript/LSAndTSDocResolver.ts
@@ -34,10 +34,8 @@ export class LSAndTSDocResolver {
     private createDocument = (fileName: string, content: string) => {
         const uri = pathToUrl(fileName);
         const document = this.docManager.openDocument({
-            languageId: 'svelte',
             text: content,
             uri,
-            version: 0,
         });
         this.docManager.lockDocument(uri);
         return document;
diff --git a/packages/language-server/src/svelte-check.ts b/packages/language-server/src/svelte-check.ts
index 2fcdcd0ae..fa103ba9c 100644
--- a/packages/language-server/src/svelte-check.ts
+++ b/packages/language-server/src/svelte-check.ts
@@ -3,6 +3,7 @@ import { LSConfigManager } from './ls-config';
 import { CSSPlugin, HTMLPlugin, PluginHost, SveltePlugin, TypeScriptPlugin } from './plugins';
 import { Diagnostic } from 'vscode-languageserver';
 import { Logger } from './logger';
+import { urlToPath } from './utils';
 
 /**
  * Small wrapper around PluginHost's Diagnostic Capabilities
@@ -30,17 +31,44 @@ export class SvelteCheck {
     }
 
     /**
-     * Gets diagnostics for a svelte file.
+     * Creates/updates given document
      *
-     * @param params Text and Uri of a svelte file
+     * @param doc Text and Uri of the document
      */
-    async getDiagnostics(params: { text: string; uri: string }): Promise<Diagnostic[]> {
+    upsertDocument(doc: { text: string; uri: string }) {
         this.docManager.openDocument({
-            languageId: 'svelte',
-            text: params.text,
-            uri: params.uri,
-            version: 1,
+            text: doc.text,
+            uri: doc.uri,
         });
-        return await this.pluginHost.getDiagnostics({ uri: params.uri });
+        this.docManager.markAsOpenedInClient(doc.uri);
+    }
+
+    /**
+     * Removes/closes document
+     *
+     * @param uri Uri of the document
+     */
+    removeDocument(uri: string) {
+        this.docManager.closeDocument(uri);
+        this.docManager.releaseDocument(uri);
+    }
+
+    /**
+     * Gets the diagnostics for all currently open files.
+     */
+    async getDiagnostics(): Promise<
+        { filePath: string; text: string; diagnostics: Diagnostic[] }[]
+    > {
+        return await Promise.all(
+            this.docManager.getAllOpenedByClient().map(async (doc) => {
+                const uri = doc[1].uri;
+                const diagnostics = await this.pluginHost.getDiagnostics({ uri });
+                return {
+                    filePath: urlToPath(uri) || '',
+                    text: this.docManager.documents.get(uri)?.getText() || '',
+                    diagnostics,
+                };
+            }),
+        );
     }
 }
diff --git a/packages/language-server/test/lib/documents/DocumentManager.test.ts b/packages/language-server/test/lib/documents/DocumentManager.test.ts
index 7e8327ee1..8420f101e 100644
--- a/packages/language-server/test/lib/documents/DocumentManager.test.ts
+++ b/packages/language-server/test/lib/documents/DocumentManager.test.ts
@@ -11,7 +11,7 @@ describe('Document Manager', () => {
         text: 'Hello, world!',
     };
 
-    const createTextDocument = (textDocument: TextDocumentItem) =>
+    const createTextDocument = (textDocument: Pick<TextDocumentItem, 'uri' | 'text'>) =>
         new Document(textDocument.uri, textDocument.text);
 
     it('opens documents', () => {
diff --git a/packages/language-server/test/plugins/PluginHost.test.ts b/packages/language-server/test/plugins/PluginHost.test.ts
index 9eb0f5233..7858008dd 100644
--- a/packages/language-server/test/plugins/PluginHost.test.ts
+++ b/packages/language-server/test/plugins/PluginHost.test.ts
@@ -13,10 +13,9 @@ describe('PluginHost', () => {
     };
 
     function setup<T>(pluginProviderStubs: T) {
-        const createTextDocument = (textDocument: TextDocumentItem) =>
-            new Document(textDocument.uri, textDocument.text);
-
-        const docManager = new DocumentManager(createTextDocument);
+        const docManager = new DocumentManager(
+            (textDocument) => new Document(textDocument.uri, textDocument.text),
+        );
 
         const pluginHost = new PluginHost(docManager, <any>{});
         const plugin = {
diff --git a/packages/svelte-check/README.md b/packages/svelte-check/README.md
index 3adee5ad1..2781337b1 100644
--- a/packages/svelte-check/README.md
+++ b/packages/svelte-check/README.md
@@ -54,6 +54,12 @@ Usage:
 
 `--output <human|human-verbose|machine>`
 
+`--watch` Will not exit after one pass but keep watching files for changes and rerun diagnostics.
+
+`--ignore <files/folders to ignore, relative to workspace root, comma-separated. Example: --ignore dist,build>`
+
+`--fail-on-warnings` Will also exit with error code when there are warnings
+
 ### More docs, preprocessor setup and troubleshooting
 
 [See here](/docs/README.md).
diff --git a/packages/svelte-check/package.json b/packages/svelte-check/package.json
index e80163839..dd95204e2 100644
--- a/packages/svelte-check/package.json
+++ b/packages/svelte-check/package.json
@@ -20,6 +20,7 @@
     "homepage": "https://github.com/sveltejs/language-tools#readme",
     "dependencies": {
         "chalk": "^4.0.0",
+        "chokidar": "^3.4.1",
         "glob": "^7.1.6",
         "minimist": "^1.2.5",
         "svelte-language-server": "*",
diff --git a/packages/svelte-check/src/index.ts b/packages/svelte-check/src/index.ts
index 75fafc76a..2c35cf69e 100644
--- a/packages/svelte-check/src/index.ts
+++ b/packages/svelte-check/src/index.ts
@@ -10,6 +10,7 @@ import { SvelteCheck } from 'svelte-language-server';
 import { Diagnostic, DiagnosticSeverity } from 'vscode-languageserver-protocol';
 import { URI } from 'vscode-uri';
 import { HumanFriendlyWriter, MachineFriendlyWriter, Writer } from './writers';
+import { watch } from 'chokidar';
 
 const outputFormats = ['human', 'human-verbose', 'machine'] as const;
 type OutputFormat = typeof outputFormats[number];
@@ -20,58 +21,105 @@ type Result = {
     warningCount: number;
 };
 
-async function getDiagnostics(workspaceUri: URI, writer: Writer): Promise<Result | null> {
-    writer.start(workspaceUri.fsPath);
-
-    const svelteCheck = new SvelteCheck(workspaceUri.fsPath);
-
+function openAllDocuments(
+    workspaceUri: URI,
+    filePathsToIgnore: string[],
+    svelteCheck: SvelteCheck,
+) {
     const files = glob.sync('**/*.svelte', {
         cwd: workspaceUri.fsPath,
-        ignore: ['node_modules/**'],
+        ignore: ['node_modules/**'].concat(filePathsToIgnore.map((ignore) => `${ignore}/**`)),
     });
 
     const absFilePaths = files.map((f) => path.resolve(workspaceUri.fsPath, f));
 
-    const result = {
-        fileCount: absFilePaths.length,
-        errorCount: 0,
-        warningCount: 0,
-    };
-
     for (const absFilePath of absFilePaths) {
         const text = fs.readFileSync(absFilePath, 'utf-8');
+        svelteCheck.upsertDocument({
+            uri: URI.file(absFilePath).toString(),
+            text,
+        });
+    }
+}
 
-        let res: Diagnostic[] = [];
+async function getDiagnostics(
+    workspaceUri: URI,
+    writer: Writer,
+    svelteCheck: SvelteCheck,
+): Promise<Result | null> {
+    writer.start(workspaceUri.fsPath);
 
-        try {
-            res = await svelteCheck.getDiagnostics({
-                uri: URI.file(absFilePath).toString(),
-                text,
+    try {
+        const diagnostics = await svelteCheck.getDiagnostics();
+
+        const result: Result = {
+            fileCount: diagnostics.length,
+            errorCount: 0,
+            warningCount: 0,
+        };
+
+        for (const diagnostic of diagnostics) {
+            writer.file(
+                diagnostic.diagnostics,
+                workspaceUri.fsPath,
+                path.relative(workspaceUri.fsPath, diagnostic.filePath),
+                diagnostic.text,
+            );
+
+            diagnostic.diagnostics.forEach((d: Diagnostic) => {
+                if (d.severity === DiagnosticSeverity.Error) {
+                    result.errorCount += 1;
+                } else if (d.severity === DiagnosticSeverity.Warning) {
+                    result.warningCount += 1;
+                }
             });
-        } catch (err) {
-            writer.failure(err);
-            return null;
         }
 
-        writer.file(
-            res,
-            workspaceUri.fsPath,
-            path.relative(workspaceUri.fsPath, absFilePath),
-            text,
-        );
+        writer.completion(result.fileCount, result.errorCount, result.warningCount);
+        return result;
+    } catch (err) {
+        writer.failure(err);
+        return null;
+    }
+}
 
-        res.forEach((d: Diagnostic) => {
-            if (d.severity === DiagnosticSeverity.Error) {
-                result.errorCount += 1;
-            } else if (d.severity === DiagnosticSeverity.Warning) {
-                result.warningCount += 1;
-            }
-        });
+class DiagnosticsWatcher {
+    private updateDiagnostics: any;
+
+    constructor(
+        private workspaceUri: URI,
+        private svelteCheck: SvelteCheck,
+        private writer: Writer,
+        filePathsToIgnore: string[],
+    ) {
+        watch(`${workspaceUri.fsPath}/**/*.svelte`, {
+            ignored: ['node_modules']
+                .concat(filePathsToIgnore)
+                .map((ignore) => path.join(workspaceUri.fsPath, ignore)),
+        })
+            .on('add', (path) => this.updateDocument(path))
+            .on('unlink', (path) => this.removeDocument(path))
+            .on('change', (path) => this.updateDocument(path));
     }
 
-    writer.completion(result.fileCount, result.errorCount, result.warningCount);
+    private updateDocument(path: string) {
+        const text = fs.readFileSync(path, 'utf-8');
+        this.svelteCheck.upsertDocument({ text, uri: URI.file(path).toString() });
+        this.scheduleDiagnostics();
+    }
 
-    return result;
+    private removeDocument(path: string) {
+        this.svelteCheck.removeDocument(URI.file(path).toString());
+        this.scheduleDiagnostics();
+    }
+
+    private scheduleDiagnostics() {
+        clearTimeout(this.updateDiagnostics);
+        this.updateDiagnostics = setTimeout(
+            () => getDiagnostics(this.workspaceUri, this.writer, this.svelteCheck),
+            1000,
+        );
+    }
 }
 
 (async () => {
@@ -99,12 +147,23 @@ async function getDiagnostics(workspaceUri: URI, writer: Writer): Promise<Result
         writer = new MachineFriendlyWriter(process.stdout);
     }
 
-    const result = await getDiagnostics(workspaceUri, writer);
+    const svelteCheck = new SvelteCheck(workspaceUri.fsPath);
+    const filePathsToIgnore = myArgs['ignore'].split(' ') || [];
 
-    if (result && (result as Result).errorCount === 0) {
-        process.exit(0);
+    if (myArgs['watch']) {
+        new DiagnosticsWatcher(workspaceUri, svelteCheck, writer, filePathsToIgnore);
     } else {
-        process.exit(1);
+        openAllDocuments(workspaceUri, filePathsToIgnore, svelteCheck);
+        const result = await getDiagnostics(workspaceUri, writer, svelteCheck);
+        if (
+            result &&
+            result.errorCount === 0 &&
+            (!myArgs['fail-on-warnings'] || result.warningCount === 0)
+        ) {
+            process.exit(0);
+        } else {
+            process.exit(1);
+        }
     }
 })().catch((_err) => {
     console.error(_err);
diff --git a/packages/svelte-check/src/writers.ts b/packages/svelte-check/src/writers.ts
index bbe1d1916..e565acd94 100644
--- a/packages/svelte-check/src/writers.ts
+++ b/packages/svelte-check/src/writers.ts
@@ -1,10 +1,7 @@
 import * as chalk from 'chalk';
 import { sep } from 'path';
-import { Writable } from "stream";
-import {
-    Diagnostic,
-    DiagnosticSeverity,
-} from 'vscode-languageserver-protocol';
+import { Writable } from 'stream';
+import { Diagnostic, DiagnosticSeverity } from 'vscode-languageserver-protocol';
 import { offsetAt } from 'svelte-language-server';
 
 export interface Writer {
@@ -15,8 +12,7 @@ export interface Writer {
 }
 
 export class HumanFriendlyWriter implements Writer {
-    constructor(private stream: Writable, private isVerbose = true) {
-    }
+    constructor(private stream: Writable, private isVerbose = true) {}
 
     start(workspaceDir: string) {
         if (this.isVerbose) {
@@ -36,14 +32,14 @@ export class HumanFriendlyWriter implements Writer {
             // Display location in a format that IDEs will turn into file links
             const { line, character } = diagnostic.range.start;
             // eslint-disable-next-line max-len
-            this.stream.write(`${workspaceDir}${sep}${chalk.green(filename)}:${line + 1}:${character + 1}\n`);
+            this.stream.write(
+                `${workspaceDir}${sep}${chalk.green(filename)}:${line + 1}:${character + 1}\n`,
+            );
 
             // Show some context around diagnostic range
             const startOffset = offsetAt(diagnostic.range.start, text);
             const endOffset = offsetAt(diagnostic.range.end, text);
-            const codePrev = chalk.cyan(
-                text.substring(Math.max(startOffset - 10, 0), startOffset)
-            );
+            const codePrev = chalk.cyan(text.substring(Math.max(startOffset - 10, 0), startOffset));
             const codeHighlight = chalk.magenta(text.substring(startOffset, endOffset));
             const codePost = chalk.cyan(text.substring(endOffset, endOffset + 10));
             const code = codePrev + codeHighlight + codePost;
@@ -51,29 +47,41 @@ export class HumanFriendlyWriter implements Writer {
 
             if (this.isVerbose) {
                 msg = `${diagnostic.message} ${source}\n${chalk.cyan(code)}`;
-            }
-            else {
+            } else {
                 msg = `${diagnostic.message} ${source}`;
             }
 
             if (diagnostic.severity === DiagnosticSeverity.Error) {
                 this.stream.write(`${chalk.red('Error')}: ${msg}\n`);
-            }
-            else {
+            } else {
                 this.stream.write(`${chalk.yellow('Warn')}: ${msg}\n`);
             }
 
-            this.stream.write("\n");
+            this.stream.write('\n');
         });
     }
 
-    completion(_f: number, err: number, _w: number) {
+    completion(_f: number, errorCount: number, warningCount: number) {
         this.stream.write('====================================\n');
 
-        if (err === 0) {
-            this.stream.write(chalk.green(`svelte-check found no errors\n`));
+        if (errorCount === 0 && warningCount === 0) {
+            this.stream.write(chalk.green(`svelte-check found no errors and no warnings\n`));
+        } else if (errorCount === 0) {
+            this.stream.write(
+                chalk.yellow(
+                    `svelte-check found ${warningCount} ${
+                        warningCount === 1 ? 'warning' : 'warnings'
+                    }\n`,
+                ),
+            );
         } else {
-            this.stream.write(chalk.red(`svelte-check found ${err} ${err === 1 ? 'error' : 'errors'}\n`));
+            this.stream.write(
+                chalk.red(
+                    `svelte-check found ${errorCount} ${
+                        errorCount === 1 ? 'error' : 'errors'
+                    } and ${warningCount} ${warningCount === 1 ? 'warning' : 'warnings'}\n`,
+                ),
+            );
         }
     }
 
@@ -83,8 +91,7 @@ export class HumanFriendlyWriter implements Writer {
 }
 
 export class MachineFriendlyWriter implements Writer {
-    constructor(private stream: Writable) {
-    }
+    constructor(private stream: Writable) {}
 
     private log(msg: string) {
         this.stream.write(`${new Date().getTime()} ${msg}\n`);
@@ -98,9 +105,11 @@ export class MachineFriendlyWriter implements Writer {
         diagnostics.forEach((d) => {
             const { message, severity, range } = d;
             const type =
-              severity === DiagnosticSeverity.Error ? "ERROR" :
-              severity === DiagnosticSeverity.Warning ? "WARNING" :
-              null;
+                severity === DiagnosticSeverity.Error
+                    ? 'ERROR'
+                    : severity === DiagnosticSeverity.Warning
+                    ? 'WARNING'
+                    : null;
 
             if (type) {
                 const { line, character } = range.start;
diff --git a/yarn.lock b/yarn.lock
index b27df4c98..010899896 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -497,6 +497,21 @@ chokidar@3.3.0:
   optionalDependencies:
     fsevents "~2.1.1"
 
+chokidar@^3.4.1:
+  version "3.4.1"
+  resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-3.4.1.tgz#e905bdecf10eaa0a0b1db0c664481cc4cbc22ba1"
+  integrity sha512-TQTJyr2stihpC4Sya9hs2Xh+O2wf+igjL36Y75xx2WdHuiICcn/XJza46Jwt0eT5hVpQOzo3FpY3cj3RVYLX0g==
+  dependencies:
+    anymatch "~3.1.1"
+    braces "~3.0.2"
+    glob-parent "~5.1.0"
+    is-binary-path "~2.1.0"
+    is-glob "~4.0.1"
+    normalize-path "~3.0.0"
+    readdirp "~3.4.0"
+  optionalDependencies:
+    fsevents "~2.1.2"
+
 cli-cursor@^3.1.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/cli-cursor/-/cli-cursor-3.1.0.tgz#264305a7ae490d1d03bf0c9ba7c925d1753af307"
@@ -924,6 +939,11 @@ fsevents@~2.1.1:
   resolved "https://registry.yarnpkg.com/fsevents/-/fsevents-2.1.2.tgz#4c0a1fb34bc68e543b4b82a9ec392bfbda840805"
   integrity sha512-R4wDiBwZ0KzpgOWetKDug1FZcYhqYnUYKtfZYt4mD5SBz76q0KR4Q9o7GIPamsVPGmW3EYPPJ0dOOjvx32ldZA==
 
+fsevents@~2.1.2:
+  version "2.1.3"
+  resolved "https://registry.yarnpkg.com/fsevents/-/fsevents-2.1.3.tgz#fb738703ae8d2f9fe900c33836ddebee8b97f23e"
+  integrity sha512-Auw9a4AxqWpa9GUfj370BMPzzyncfBABW8Mab7BGWBYDj4Isgq+cDKtx0i6u9jcX9pQDnswsaaOTgTmA5pEjuQ==
+
 function-bind@^1.1.1:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/function-bind/-/function-bind-1.1.1.tgz#a56899d3ea3c9bab874bb9773b7c5ede92f4895d"
@@ -1647,6 +1667,11 @@ picomatch@^2.0.4:
   resolved "https://registry.yarnpkg.com/picomatch/-/picomatch-2.2.1.tgz#21bac888b6ed8601f831ce7816e335bc779f0a4a"
   integrity sha512-ISBaA8xQNmwELC7eOjqFKMESB2VIqt4PPDD0nsS95b/9dZXvVKOlz9keMSnoGGKcOHXfTvDD6WMaRoSc9UuhRA==
 
+picomatch@^2.2.1:
+  version "2.2.2"
+  resolved "https://registry.yarnpkg.com/picomatch/-/picomatch-2.2.2.tgz#21f333e9b6b8eaff02468f5146ea406d345f4dad"
+  integrity sha512-q0M/9eZHzmr0AulXyPwNfZjtwZ/RBZlbN3K3CErVrk50T2ASYI7Bye0EvekFY3IP1Nt2DHu0re+V2ZHIpMkuWg==
+
 pify@^2.0.0:
   version "2.3.0"
   resolved "https://registry.yarnpkg.com/pify/-/pify-2.3.0.tgz#ed141a6ac043a849ea588498e7dca8b15330e90c"
@@ -1701,6 +1726,13 @@ readdirp@~3.2.0:
   dependencies:
     picomatch "^2.0.4"
 
+readdirp@~3.4.0:
+  version "3.4.0"
+  resolved "https://registry.yarnpkg.com/readdirp/-/readdirp-3.4.0.tgz#9fdccdf9e9155805449221ac645e8303ab5b9ada"
+  integrity sha512-0xe001vZBnJEK+uKcj8qOhyAKPzIT+gStxWr3LCB0DwcXR5NZJ3IaC+yGnHCYzB/S7ov3m3EEbZI2zeNvX+hGQ==
+  dependencies:
+    picomatch "^2.2.1"
+
 regenerator-runtime@^0.13.4:
   version "0.13.4"
   resolved "https://registry.yarnpkg.com/regenerator-runtime/-/regenerator-runtime-0.13.4.tgz#e96bf612a3362d12bb69f7e8f74ffeab25c7ac91"