diff --git a/src/Chunk.ts b/src/Chunk.ts
index 2f19bd1e7d8..94eab50c2fa 100644
--- a/src/Chunk.ts
+++ b/src/Chunk.ts
@@ -450,7 +450,7 @@ export default class Chunk {
 			const extension = extname(sanitizedId);
 			const fileName = renderNamePattern(pattern, 'output.entryFileNames', {
 				assetExtname: () => (NON_ASSET_EXTENSIONS.includes(extension) ? '' : extension),
-				ext: () => extension.substr(1),
+				ext: () => extension.substring(1),
 				extname: () => extension,
 				format: () => options.format as string,
 				name: () => this.getChunkName()
@@ -466,7 +466,7 @@ export default class Chunk {
 			const extension = extname(sanitizedId);
 			const fileName = renderNamePattern(pattern, 'output.entryFileNames', {
 				assetExtname: () => (NON_ASSET_EXTENSIONS.includes(extension) ? '' : extension),
-				ext: () => extension.substr(1),
+				ext: () => extension.substring(1),
 				extname: () => extension,
 				format: () => options.format as string,
 				name: () => getAliasName(sanitizedId)
@@ -1161,7 +1161,7 @@ export default class Chunk {
 			let imported: string;
 			let needsLiveBinding = false;
 			if (exportName[0] === '*') {
-				const id = exportName.substr(1);
+				const id = exportName.substring(1);
 				if (interop(id) === 'defaultOnly') {
 					this.inputOptions.onwarn(errUnexpectedNamespaceReexport(id));
 				}
diff --git a/src/ast/nodes/MetaProperty.ts b/src/ast/nodes/MetaProperty.ts
index e8868968998..5ec993c9bc0 100644
--- a/src/ast/nodes/MetaProperty.ts
+++ b/src/ast/nodes/MetaProperty.ts
@@ -43,7 +43,7 @@ export default class MetaProperty extends NodeBase {
 	getReferencedFileName(outputPluginDriver: PluginDriver): string | null {
 		const metaProperty = this.metaProperty as string | null;
 		if (metaProperty && metaProperty.startsWith(FILE_PREFIX)) {
-			return outputPluginDriver.getFileName(metaProperty.substr(FILE_PREFIX.length));
+			return outputPluginDriver.getFileName(metaProperty.substring(FILE_PREFIX.length));
 		}
 		return null;
 	}
@@ -91,7 +91,7 @@ export default class MetaProperty extends NodeBase {
 			let chunkReferenceId: string | null = null;
 			let fileName: string;
 			if (metaProperty.startsWith(FILE_PREFIX)) {
-				referenceId = metaProperty.substr(FILE_PREFIX.length);
+				referenceId = metaProperty.substring(FILE_PREFIX.length);
 				fileName = outputPluginDriver.getFileName(referenceId);
 			} else if (metaProperty.startsWith(ASSET_PREFIX)) {
 				warnDeprecation(
@@ -99,7 +99,7 @@ export default class MetaProperty extends NodeBase {
 					true,
 					this.context.options
 				);
-				assetReferenceId = metaProperty.substr(ASSET_PREFIX.length);
+				assetReferenceId = metaProperty.substring(ASSET_PREFIX.length);
 				fileName = outputPluginDriver.getFileName(assetReferenceId);
 			} else {
 				warnDeprecation(
@@ -107,7 +107,7 @@ export default class MetaProperty extends NodeBase {
 					true,
 					this.context.options
 				);
-				chunkReferenceId = metaProperty.substr(CHUNK_PREFIX.length);
+				chunkReferenceId = metaProperty.substring(CHUNK_PREFIX.length);
 				fileName = outputPluginDriver.getFileName(chunkReferenceId);
 			}
 			const relativePath = normalize(relative(dirname(chunkId), fileName));
diff --git a/src/utils/FileEmitter.ts b/src/utils/FileEmitter.ts
index a71b5b0060d..dcb4579edf2 100644
--- a/src/utils/FileEmitter.ts
+++ b/src/utils/FileEmitter.ts
@@ -42,16 +42,17 @@ function generateAssetFileName(
 				: outputOptions.assetFileNames,
 			'output.assetFileNames',
 			{
-				ext: () => extname(emittedName).substr(1),
+				ext: () => extname(emittedName).substring(1),
 				extname: () => extname(emittedName),
 				hash() {
-					const hash = createHash();
-					hash.update(emittedName);
-					hash.update(':');
-					hash.update(source);
-					return hash.digest('hex').substr(0, 8);
+					return createHash()
+						.update(emittedName)
+						.update(':')
+						.update(source)
+						.digest('hex')
+						.substring(0, 8);
 				},
-				name: () => emittedName.substr(0, emittedName.length - extname(emittedName).length)
+				name: () => emittedName.substring(0, emittedName.length - extname(emittedName).length)
 			}
 		),
 		bundle
diff --git a/src/utils/relativeId.ts b/src/utils/relativeId.ts
index 0502c5563d0..743f6a27ef2 100644
--- a/src/utils/relativeId.ts
+++ b/src/utils/relativeId.ts
@@ -2,7 +2,7 @@ import { basename, extname, isAbsolute, relative, resolve } from './path';
 
 export function getAliasName(id: string): string {
 	const base = basename(id);
-	return base.substr(0, base.length - extname(id).length);
+	return base.substring(0, base.length - extname(id).length);
 }
 
 export default function relativeId(id: string): string {
diff --git a/src/utils/renderNamePattern.ts b/src/utils/renderNamePattern.ts
index 0bf89b563b7..cccff7f8de5 100644
--- a/src/utils/renderNamePattern.ts
+++ b/src/utils/renderNamePattern.ts
@@ -35,7 +35,7 @@ export function makeUnique(name: string, existingNames: Record<string, unknown>)
 	if (!existingNamesLowercase.has(name.toLocaleLowerCase())) return name;
 
 	const ext = extname(name);
-	name = name.substr(0, name.length - ext.length);
+	name = name.substring(0, name.length - ext.length);
 	let uniqueName: string,
 		uniqueIndex = 1;
 	while (existingNamesLowercase.has((uniqueName = name + ++uniqueIndex + ext).toLowerCase()));