diff --git a/packages/language-server/src/lib/DiagnosticsManager.ts b/packages/language-server/src/lib/DiagnosticsManager.ts
index 54e4f0122..ac94a25f0 100644
--- a/packages/language-server/src/lib/DiagnosticsManager.ts
+++ b/packages/language-server/src/lib/DiagnosticsManager.ts
@@ -1,9 +1,18 @@
-import { _Connection, TextDocumentIdentifier, Diagnostic } from 'vscode-languageserver';
+import {
+    Connection,
+    TextDocumentIdentifier,
+    Diagnostic,
+    CancellationTokenSource,
+    CancellationToken
+} from 'vscode-languageserver';
 import { DocumentManager, Document } from './documents';
 import { debounceThrottle } from '../utils';
 
-export type SendDiagnostics = _Connection['sendDiagnostics'];
-export type GetDiagnostics = (doc: TextDocumentIdentifier) => Thenable<Diagnostic[]>;
+export type SendDiagnostics = Connection['sendDiagnostics'];
+export type GetDiagnostics = (
+    doc: TextDocumentIdentifier,
+    cancellationToken?: CancellationToken
+) => Thenable<Diagnostic[]>;
 
 export class DiagnosticsManager {
     constructor(
@@ -13,6 +22,7 @@ export class DiagnosticsManager {
     ) {}
 
     private pendingUpdates = new Set<Document>();
+    private cancellationTokens = new Map<string, { cancel: () => void }>();
 
     private updateAll() {
         this.docManager.getAllOpenedByClient().forEach((doc) => {
@@ -21,14 +31,43 @@ export class DiagnosticsManager {
         this.pendingUpdates.clear();
     }
 
-    scheduleUpdateAll = debounceThrottle(() => this.updateAll(), 1000);
+    scheduleUpdateAll() {
+        this.cancellationTokens.forEach((token) => token.cancel());
+        this.cancellationTokens.clear();
+        this.pendingUpdates.clear();
+        this.debouncedUpdateAll();
+    }
+
+    private debouncedUpdateAll = debounceThrottle(() => this.updateAll(), 1000);
 
     private async update(document: Document) {
-        const diagnostics = await this.getDiagnostics({ uri: document.getURL() });
+        const uri = document.getURL();
+        this.cancelStarted(uri);
+
+        const tokenSource = new CancellationTokenSource();
+        this.cancellationTokens.set(uri, tokenSource);
+
+        const diagnostics = await this.getDiagnostics(
+            { uri: document.getURL() },
+            tokenSource.token
+        );
         this.sendDiagnostics({
             uri: document.getURL(),
             diagnostics
         });
+
+        tokenSource.dispose();
+
+        if (this.cancellationTokens.get(uri) === tokenSource) {
+            this.cancellationTokens.delete(uri);
+        }
+    }
+
+    cancelStarted(uri: string) {
+        const started = this.cancellationTokens.get(uri);
+        if (started) {
+            started.cancel();
+        }
     }
 
     removeDiagnostics(document: Document) {
@@ -44,6 +83,7 @@ export class DiagnosticsManager {
             return;
         }
 
+        this.cancelStarted(document.getURL());
         this.pendingUpdates.add(document);
         this.scheduleBatchUpdate();
     }
@@ -53,5 +93,5 @@ export class DiagnosticsManager {
             this.update(doc);
         });
         this.pendingUpdates.clear();
-    }, 750);
+    }, 700);
 }
diff --git a/packages/language-server/src/plugins/PluginHost.ts b/packages/language-server/src/plugins/PluginHost.ts
index 2fa463401..b239c21ee 100644
--- a/packages/language-server/src/plugins/PluginHost.ts
+++ b/packages/language-server/src/plugins/PluginHost.ts
@@ -76,7 +76,10 @@ export class PluginHost implements LSProvider, OnWatchFileChanges {
         this.deferredRequests = {};
     }
 
-    async getDiagnostics(textDocument: TextDocumentIdentifier): Promise<Diagnostic[]> {
+    async getDiagnostics(
+        textDocument: TextDocumentIdentifier,
+        cancellationToken?: CancellationToken
+    ): Promise<Diagnostic[]> {
         const document = this.getDocument(textDocument.uri);
 
         if (
@@ -96,7 +99,7 @@ export class PluginHost implements LSProvider, OnWatchFileChanges {
         return flatten(
             await this.execute<Diagnostic[]>(
                 'getDiagnostics',
-                [document],
+                [document, cancellationToken],
                 ExecuteMode.Collect,
                 'high'
             )
diff --git a/packages/language-server/src/plugins/svelte/SveltePlugin.ts b/packages/language-server/src/plugins/svelte/SveltePlugin.ts
index fad2fc897..379ad07d8 100644
--- a/packages/language-server/src/plugins/svelte/SveltePlugin.ts
+++ b/packages/language-server/src/plugins/svelte/SveltePlugin.ts
@@ -49,7 +49,10 @@ export class SveltePlugin
 
     constructor(private configManager: LSConfigManager) {}
 
-    async getDiagnostics(document: Document): Promise<Diagnostic[]> {
+    async getDiagnostics(
+        document: Document,
+        cancellationToken?: CancellationToken
+    ): Promise<Diagnostic[]> {
         if (!this.featureEnabled('diagnostics') || !this.configManager.getIsTrusted()) {
             return [];
         }
@@ -57,7 +60,8 @@ export class SveltePlugin
         return getDiagnostics(
             document,
             await this.getSvelteDoc(document),
-            this.configManager.getConfig().svelte.compilerWarnings
+            this.configManager.getConfig().svelte.compilerWarnings,
+            cancellationToken
         );
     }
 
diff --git a/packages/language-server/src/plugins/svelte/features/getDiagnostics.ts b/packages/language-server/src/plugins/svelte/features/getDiagnostics.ts
index ae53c4c2b..dbc21bfb8 100644
--- a/packages/language-server/src/plugins/svelte/features/getDiagnostics.ts
+++ b/packages/language-server/src/plugins/svelte/features/getDiagnostics.ts
@@ -1,6 +1,12 @@
 // @ts-ignore
 import { Warning } from 'svelte/types/compiler/interfaces';
-import { Diagnostic, DiagnosticSeverity, Position, Range } from 'vscode-languageserver';
+import {
+    CancellationToken,
+    Diagnostic,
+    DiagnosticSeverity,
+    Position,
+    Range
+} from 'vscode-languageserver';
 import {
     Document,
     isInTag,
@@ -19,15 +25,20 @@ import { SvelteDocument, TranspileErrorSource } from '../SvelteDocument';
 export async function getDiagnostics(
     document: Document,
     svelteDoc: SvelteDocument,
-    settings: CompilerWarningsSettings
+    settings: CompilerWarningsSettings,
+    cancellationToken?: CancellationToken
 ): Promise<Diagnostic[]> {
     const config = await svelteDoc.config;
     if (config?.loadConfigError) {
         return getConfigLoadErrorDiagnostics(config.loadConfigError);
     }
 
+    if (cancellationToken?.isCancellationRequested) {
+        return [];
+    }
+
     try {
-        return await tryGetDiagnostics(document, svelteDoc, settings);
+        return await tryGetDiagnostics(document, svelteDoc, settings, cancellationToken);
     } catch (error) {
         return getPreprocessErrorDiagnostics(document, error);
     }
@@ -39,12 +50,19 @@ export async function getDiagnostics(
 async function tryGetDiagnostics(
     document: Document,
     svelteDoc: SvelteDocument,
-    settings: CompilerWarningsSettings
+    settings: CompilerWarningsSettings,
+    cancellationToken: CancellationToken | undefined
 ): Promise<Diagnostic[]> {
     const transpiled = await svelteDoc.getTranspiled();
+    if (cancellationToken?.isCancellationRequested) {
+        return [];
+    }
 
     try {
         const res = await svelteDoc.getCompiled();
+        if (cancellationToken?.isCancellationRequested) {
+            return [];
+        }
         return (((res.stats as any)?.warnings || res.warnings || []) as Warning[])
             .filter((warning) => settings[warning.code] !== 'ignore')
             .map((warning) => {
@@ -65,7 +83,7 @@ async function tryGetDiagnostics(
             .map((diag) => adjustMappings(diag, document))
             .filter((diag) => isNoFalsePositive(diag, document));
     } catch (err) {
-        return (await createParserErrorDiagnostic(err, document))
+        return createParserErrorDiagnostic(err, document)
             .map((diag) => mapObjWithRangeToOriginal(transpiled, diag))
             .map((diag) => adjustMappings(diag, document));
     }
@@ -74,7 +92,7 @@ async function tryGetDiagnostics(
 /**
  * Try to infer a nice diagnostic error message from the compilation error.
  */
-async function createParserErrorDiagnostic(error: any, document: Document) {
+function createParserErrorDiagnostic(error: any, document: Document) {
     const start = error.start || { line: 1, column: 0 };
     const end = error.end || start;
     const diagnostic: Diagnostic = {
diff --git a/packages/language-server/src/plugins/typescript/features/DiagnosticsProvider.ts b/packages/language-server/src/plugins/typescript/features/DiagnosticsProvider.ts
index 0015dd762..dc6b61f81 100644
--- a/packages/language-server/src/plugins/typescript/features/DiagnosticsProvider.ts
+++ b/packages/language-server/src/plugins/typescript/features/DiagnosticsProvider.ts
@@ -80,11 +80,20 @@ export class DiagnosticsProviderImpl implements DiagnosticsProvider {
             ];
         }
 
-        let diagnostics: ts.Diagnostic[] = [
-            ...lang.getSyntacticDiagnostics(tsDoc.filePath),
-            ...lang.getSuggestionDiagnostics(tsDoc.filePath),
-            ...lang.getSemanticDiagnostics(tsDoc.filePath)
-        ];
+        let diagnostics: ts.Diagnostic[] = lang.getSyntacticDiagnostics(tsDoc.filePath);
+        const checkers = [lang.getSuggestionDiagnostics, lang.getSemanticDiagnostics];
+
+        for (const checker of checkers) {
+            if (cancellationToken) {
+                // wait a bit so the event loop can check for cancellation
+                // or let completion go first
+                await new Promise((resolve) => setTimeout(resolve, 10));
+                if (cancellationToken.isCancellationRequested) {
+                    return [];
+                }
+            }
+            diagnostics.push(...checker.call(lang, tsDoc.filePath));
+        }
 
         const additionalStoreDiagnostics: ts.Diagnostic[] = [];
         const notGenerated = isNotGenerated(tsDoc.getFullText());
diff --git a/packages/language-server/src/server.ts b/packages/language-server/src/server.ts
index feb2f4de4..fcc031466 100644
--- a/packages/language-server/src/server.ts
+++ b/packages/language-server/src/server.ts
@@ -353,6 +353,7 @@ export function startServer(options?: LSOptions) {
 
     connection.onDidCloseTextDocument((evt) => docManager.closeDocument(evt.textDocument.uri));
     connection.onDidChangeTextDocument((evt) => {
+        diagnosticsManager.cancelStarted(evt.textDocument.uri);
         docManager.updateDocument(evt.textDocument, evt.contentChanges);
         pluginHost.didUpdateDocument();
     });
@@ -468,7 +469,7 @@ export function startServer(options?: LSOptions) {
         refreshCrossFilesSemanticFeatures();
     }
 
-    connection.onDidSaveTextDocument(diagnosticsManager.scheduleUpdateAll);
+    connection.onDidSaveTextDocument(diagnosticsManager.scheduleUpdateAll.bind(diagnosticsManager));
     connection.onNotification('$/onDidChangeTsOrJsFile', async (e: any) => {
         const path = urlToPath(e.uri);
         if (path) {
diff --git a/packages/language-server/test/plugins/PluginHost.test.ts b/packages/language-server/test/plugins/PluginHost.test.ts
index d18c76403..c7b1807c5 100644
--- a/packages/language-server/test/plugins/PluginHost.test.ts
+++ b/packages/language-server/test/plugins/PluginHost.test.ts
@@ -52,7 +52,7 @@ describe('PluginHost', () => {
         await pluginHost.getDiagnostics(textDocument);
 
         sinon.assert.calledOnce(plugin.getDiagnostics);
-        sinon.assert.calledWithExactly(plugin.getDiagnostics, document);
+        sinon.assert.calledWithExactly(plugin.getDiagnostics, document, undefined);
     });
 
     it('executes doHover on plugins', async () => {