diff --git a/src/generators/Generator.ts b/src/generators/Generator.ts
index 18135a3045..7d207b46ce 100644
--- a/src/generators/Generator.ts
+++ b/src/generators/Generator.ts
@@ -1,15 +1,15 @@
 import MagicString, { Bundle } from 'magic-string';
 import { walk } from 'estree-walker';
-import isReference from '../utils/isReference';
-import flattenReference from '../utils/flattenReference';
-import globalWhitelist from '../utils/globalWhitelist';
-import reservedNames from '../utils/reservedNames';
-import namespaces from '../utils/namespaces';
-import { removeNode, removeObjectKey } from '../utils/removeNode';
-import getIntro from './shared/utils/getIntro';
-import getOutro from './shared/utils/getOutro';
-import processCss from './shared/processCss';
-import annotateWithScopes from '../utils/annotateWithScopes';
+import isReference from '../utils/isReference.ts';
+import flattenReference from '../utils/flattenReference.ts';
+import globalWhitelist from '../utils/globalWhitelist.ts';
+import reservedNames from '../utils/reservedNames.ts';
+import namespaces from '../utils/namespaces.ts';
+import { removeNode, removeObjectKey } from '../utils/removeNode.ts';
+import getIntro from './shared/utils/getIntro.ts';
+import getOutro from './shared/utils/getOutro.ts';
+import processCss from './shared/processCss.ts';
+import annotateWithScopes from '../utils/annotateWithScopes.ts';
 
 const test = typeof global !== 'undefined' && global.__svelte_test;
 
diff --git a/src/generators/dom/Block.ts b/src/generators/dom/Block.ts
index b471b7f00f..40520e20a9 100644
--- a/src/generators/dom/Block.ts
+++ b/src/generators/dom/Block.ts
@@ -1,4 +1,4 @@
-import CodeBuilder from '../../utils/CodeBuilder';
+import CodeBuilder from '../../utils/CodeBuilder.ts';
 import deindent from '../../utils/deindent.js';
 
 export default class Block {
diff --git a/src/generators/dom/index.ts b/src/generators/dom/index.ts
index 4614712b90..e4fa2c6f71 100644
--- a/src/generators/dom/index.ts
+++ b/src/generators/dom/index.ts
@@ -1,14 +1,14 @@
 import MagicString from 'magic-string';
 import { parseExpressionAt } from 'acorn';
-import annotateWithScopes from '../../utils/annotateWithScopes';
-import isReference from '../../utils/isReference';
+import annotateWithScopes from '../../utils/annotateWithScopes.ts';
+import isReference from '../../utils/isReference.ts';
 import { walk } from 'estree-walker';
 import deindent from '../../utils/deindent.js';
-import CodeBuilder from '../../utils/CodeBuilder';
-import visit from './visit';
-import shared from './shared';
-import Generator from '../Generator';
-import preprocess from './preprocess';
+import CodeBuilder from '../../utils/CodeBuilder.ts';
+import visit from './visit.ts';
+import shared from './shared.ts';
+import Generator from '../Generator.ts';
+import preprocess from './preprocess.ts';
 
 class DomGenerator extends Generator {
 	constructor ( parsed, source, name, options ) {
diff --git a/src/generators/dom/preprocess.ts b/src/generators/dom/preprocess.ts
index 7d26c5a2c0..0de5c21040 100644
--- a/src/generators/dom/preprocess.ts
+++ b/src/generators/dom/preprocess.ts
@@ -1,5 +1,5 @@
-import Block from './Block';
-import { trimStart, trimEnd } from '../../utils/trim';
+import Block from './Block.ts';
+import { trimStart, trimEnd } from '../../utils/trim.ts';
 import { assign } from '../../shared/index.js';
 
 function isElseIf ( node ) {
diff --git a/src/generators/dom/visit.ts b/src/generators/dom/visit.ts
index e37a8c7fd8..fc1f539f50 100644
--- a/src/generators/dom/visit.ts
+++ b/src/generators/dom/visit.ts
@@ -1,4 +1,4 @@
-import visitors from './visitors/index';
+import visitors from './visitors/index.ts';
 
 export default function visit ( generator, block, state, node ) {
 	const visitor = visitors[ node.type ];
diff --git a/src/generators/dom/visitors/Component/Binding.ts b/src/generators/dom/visitors/Component/Binding.ts
index 19eb5b40d0..4339f38697 100644
--- a/src/generators/dom/visitors/Component/Binding.ts
+++ b/src/generators/dom/visitors/Component/Binding.ts
@@ -1,6 +1,6 @@
 import deindent from '../../../../utils/deindent.js';
-import flattenReference from '../../../../utils/flattenReference';
-import getSetter from '../shared/binding/getSetter';
+import flattenReference from '../../../../utils/flattenReference.ts';
+import getSetter from '../shared/binding/getSetter.ts';
 
 export default function visitBinding ( generator, block, state, node, attribute, local ) {
 	const { name } = flattenReference( attribute.value );
diff --git a/src/generators/dom/visitors/Component/Component.ts b/src/generators/dom/visitors/Component/Component.ts
index 1748a2c6a9..a74af5f8fe 100644
--- a/src/generators/dom/visitors/Component/Component.ts
+++ b/src/generators/dom/visitors/Component/Component.ts
@@ -1,10 +1,10 @@
 import deindent from '../../../../utils/deindent.js';
-import CodeBuilder from '../../../../utils/CodeBuilder';
-import visit from '../../visit';
-import visitAttribute from './Attribute';
-import visitEventHandler from './EventHandler';
-import visitBinding from './Binding';
-import visitRef from './Ref';
+import CodeBuilder from '../../../../utils/CodeBuilder.ts';
+import visit from '../../visit.ts';
+import visitAttribute from './Attribute.ts';
+import visitEventHandler from './EventHandler.ts';
+import visitBinding from './Binding.ts';
+import visitRef from './Ref.ts';
 
 function stringifyProps ( props ) {
 	if ( !props.length ) return '{}';
diff --git a/src/generators/dom/visitors/EachBlock.ts b/src/generators/dom/visitors/EachBlock.ts
index 5cc169e500..1834f35bc3 100644
--- a/src/generators/dom/visitors/EachBlock.ts
+++ b/src/generators/dom/visitors/EachBlock.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../utils/deindent.js';
-import visit from '../visit';
+import visit from '../visit.ts';
 
 export default function visitEachBlock ( generator, block, state, node ) {
 	const each_block = generator.getUniqueName( `each_block` );
diff --git a/src/generators/dom/visitors/Element/Attribute.ts b/src/generators/dom/visitors/Element/Attribute.ts
index bd7b7591b2..1457d00698 100644
--- a/src/generators/dom/visitors/Element/Attribute.ts
+++ b/src/generators/dom/visitors/Element/Attribute.ts
@@ -1,6 +1,6 @@
-import attributeLookup from './lookup';
+import attributeLookup from './lookup.ts';
 import deindent from '../../../../utils/deindent.js';
-import getStaticAttributeValue from './getStaticAttributeValue';
+import getStaticAttributeValue from './getStaticAttributeValue.ts';
 
 export default function visitAttribute ( generator, block, state, node, attribute ) {
 	const name = attribute.name;
diff --git a/src/generators/dom/visitors/Element/Binding.ts b/src/generators/dom/visitors/Element/Binding.ts
index 92b2207942..ddf978dbbd 100644
--- a/src/generators/dom/visitors/Element/Binding.ts
+++ b/src/generators/dom/visitors/Element/Binding.ts
@@ -1,7 +1,7 @@
 import deindent from '../../../../utils/deindent.js';
-import flattenReference from '../../../../utils/flattenReference';
-import getSetter from '../shared/binding/getSetter';
-import getStaticAttributeValue from './getStaticAttributeValue';
+import flattenReference from '../../../../utils/flattenReference.ts';
+import getSetter from '../shared/binding/getSetter.ts';
+import getStaticAttributeValue from './getStaticAttributeValue.ts';
 
 export default function visitBinding ( generator, block, state, node, attribute ) {
 	const { name, parts } = flattenReference( attribute.value );
diff --git a/src/generators/dom/visitors/Element/Element.ts b/src/generators/dom/visitors/Element/Element.ts
index eb61877944..17bf3f396b 100644
--- a/src/generators/dom/visitors/Element/Element.ts
+++ b/src/generators/dom/visitors/Element/Element.ts
@@ -1,12 +1,12 @@
 import deindent from '../../../../utils/deindent.js';
-import visit from '../../visit';
-import visitComponent from '../Component/Component';
-import visitWindow from './meta/Window';
-import visitAttribute from './Attribute';
-import visitEventHandler from './EventHandler';
-import visitBinding from './Binding';
-import visitRef from './Ref';
-import addTransitions from './addTransitions';
+import visit from '../../visit.ts';
+import visitComponent from '../Component/Component.ts';
+import visitWindow from './meta/Window.ts';
+import visitAttribute from './Attribute.ts';
+import visitEventHandler from './EventHandler.ts';
+import visitBinding from './Binding.ts';
+import visitRef from './Ref.ts';
+import addTransitions from './addTransitions.ts';
 
 const meta = {
 	':Window': visitWindow
diff --git a/src/generators/dom/visitors/Element/EventHandler.ts b/src/generators/dom/visitors/Element/EventHandler.ts
index 52134440b1..a5d72131f4 100644
--- a/src/generators/dom/visitors/Element/EventHandler.ts
+++ b/src/generators/dom/visitors/Element/EventHandler.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../../utils/deindent.js';
-import flattenReference from '../../../../utils/flattenReference';
+import flattenReference from '../../../../utils/flattenReference.ts';
 
 export default function visitEventHandler ( generator, block, state, node, attribute ) {
 	const name = attribute.name;
diff --git a/src/generators/dom/visitors/Element/meta/Window.ts b/src/generators/dom/visitors/Element/meta/Window.ts
index 2d7dba9cba..be847abfe9 100644
--- a/src/generators/dom/visitors/Element/meta/Window.ts
+++ b/src/generators/dom/visitors/Element/meta/Window.ts
@@ -1,4 +1,4 @@
-import flattenReference from '../../../../../utils/flattenReference';
+import flattenReference from '../../../../../utils/flattenReference.ts';
 import deindent from '../../../../../utils/deindent.js';
 
 const associatedEvents = {
diff --git a/src/generators/dom/visitors/IfBlock.ts b/src/generators/dom/visitors/IfBlock.ts
index d0b58f40d7..968cc734b5 100644
--- a/src/generators/dom/visitors/IfBlock.ts
+++ b/src/generators/dom/visitors/IfBlock.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../utils/deindent.js';
-import visit from '../visit';
+import visit from '../visit.ts';
 
 function isElseIf ( node ) {
 	return node && node.children.length === 1 && node.children[0].type === 'IfBlock';
diff --git a/src/generators/dom/visitors/index.ts b/src/generators/dom/visitors/index.ts
index 0b8df5ebf4..a6802130ad 100644
--- a/src/generators/dom/visitors/index.ts
+++ b/src/generators/dom/visitors/index.ts
@@ -1,10 +1,10 @@
-import EachBlock from './EachBlock';
-import Element from './Element/Element';
-import IfBlock from './IfBlock';
-import MustacheTag from './MustacheTag';
-import RawMustacheTag from './RawMustacheTag';
-import Text from './Text';
-import YieldTag from './YieldTag';
+import EachBlock from './EachBlock.ts';
+import Element from './Element/Element.ts';
+import IfBlock from './IfBlock.ts';
+import MustacheTag from './MustacheTag.ts';
+import RawMustacheTag from './RawMustacheTag.ts';
+import Text from './Text.ts';
+import YieldTag from './YieldTag.ts';
 
 export default {
 	EachBlock,
diff --git a/src/generators/server-side-rendering/Block.ts b/src/generators/server-side-rendering/Block.ts
index 11bb494a89..3556c6e76a 100644
--- a/src/generators/server-side-rendering/Block.ts
+++ b/src/generators/server-side-rendering/Block.ts
@@ -1,5 +1,5 @@
 import deindent from '../../utils/deindent.js';
-import flattenReference from '../../utils/flattenReference';
+import flattenReference from '../../utils/flattenReference.ts';
 
 export default class Block {
 	constructor ( options ) {
diff --git a/src/generators/server-side-rendering/index.ts b/src/generators/server-side-rendering/index.ts
index 657f598c67..4cebd26884 100644
--- a/src/generators/server-side-rendering/index.ts
+++ b/src/generators/server-side-rendering/index.ts
@@ -1,7 +1,7 @@
 import deindent from '../../utils/deindent.js';
-import Generator from '../Generator';
-import Block from './Block';
-import visit from './visit';
+import Generator from '../Generator.ts';
+import Block from './Block.ts';
+import visit from './visit.ts';
 
 class SsrGenerator extends Generator {
 	constructor ( parsed, source, name, options ) {
diff --git a/src/generators/server-side-rendering/visit.ts b/src/generators/server-side-rendering/visit.ts
index ac75e0af03..74544ce12f 100644
--- a/src/generators/server-side-rendering/visit.ts
+++ b/src/generators/server-side-rendering/visit.ts
@@ -1,4 +1,4 @@
-import visitors from './visitors/index';
+import visitors from './visitors/index.ts';
 
 export default function visit ( generator, fragment, node ) {
 	const visitor = visitors[ node.type ];
diff --git a/src/generators/server-side-rendering/visitors/Component.ts b/src/generators/server-side-rendering/visitors/Component.ts
index 14ab2ca8f7..0ef08968b3 100644
--- a/src/generators/server-side-rendering/visitors/Component.ts
+++ b/src/generators/server-side-rendering/visitors/Component.ts
@@ -1,5 +1,5 @@
-import flattenReference from '../../../utils/flattenReference';
-import visit from '../visit';
+import flattenReference from '../../../utils/flattenReference.ts';
+import visit from '../visit.ts';
 
 export default function visitComponent ( generator, block, node ) {
 	function stringify ( chunk ) {
diff --git a/src/generators/server-side-rendering/visitors/EachBlock.ts b/src/generators/server-side-rendering/visitors/EachBlock.ts
index f09f334cf3..1e90758047 100644
--- a/src/generators/server-side-rendering/visitors/EachBlock.ts
+++ b/src/generators/server-side-rendering/visitors/EachBlock.ts
@@ -1,4 +1,4 @@
-import visit from '../visit';
+import visit from '../visit.ts';
 
 export default function visitEachBlock ( generator, block, node ) {
 	const { dependencies, snippet } = block.contextualise( node.expression );
diff --git a/src/generators/server-side-rendering/visitors/Element.ts b/src/generators/server-side-rendering/visitors/Element.ts
index 20ac1b20ed..bbc08bb2dd 100644
--- a/src/generators/server-side-rendering/visitors/Element.ts
+++ b/src/generators/server-side-rendering/visitors/Element.ts
@@ -1,7 +1,7 @@
-import visitComponent from './Component';
-import isVoidElementName from '../../../utils/isVoidElementName';
-import visit from '../visit';
-import visitWindow from './meta/Window';
+import visitComponent from './Component.ts';
+import isVoidElementName from '../../../utils/isVoidElementName.ts';
+import visit from '../visit.ts';
+import visitWindow from './meta/Window.ts';
 
 const meta = {
 	':Window': visitWindow
diff --git a/src/generators/server-side-rendering/visitors/IfBlock.ts b/src/generators/server-side-rendering/visitors/IfBlock.ts
index 0b7e2b912a..10355913d8 100644
--- a/src/generators/server-side-rendering/visitors/IfBlock.ts
+++ b/src/generators/server-side-rendering/visitors/IfBlock.ts
@@ -1,4 +1,4 @@
-import visit from '../visit';
+import visit from '../visit.ts';
 
 export default function visitIfBlock ( generator, block, node ) {
 	const { snippet } = block.contextualise( node.expression );
diff --git a/src/generators/server-side-rendering/visitors/index.ts b/src/generators/server-side-rendering/visitors/index.ts
index cf905ad41b..1067dcf733 100644
--- a/src/generators/server-side-rendering/visitors/index.ts
+++ b/src/generators/server-side-rendering/visitors/index.ts
@@ -1,11 +1,11 @@
-import Comment from './Comment';
-import EachBlock from './EachBlock';
-import Element from './Element';
-import IfBlock from './IfBlock';
-import MustacheTag from './MustacheTag';
-import RawMustacheTag from './RawMustacheTag';
-import Text from './Text';
-import YieldTag from './YieldTag';
+import Comment from './Comment.ts';
+import EachBlock from './EachBlock.ts';
+import Element from './Element.ts';
+import IfBlock from './IfBlock.ts';
+import MustacheTag from './MustacheTag.ts';
+import RawMustacheTag from './RawMustacheTag.ts';
+import Text from './Text.ts';
+import YieldTag from './YieldTag.ts';
 
 export default {
 	Comment,
diff --git a/src/generators/shared/utils/getIntro.ts b/src/generators/shared/utils/getIntro.ts
index 6b9bf97815..5738eeee1d 100644
--- a/src/generators/shared/utils/getIntro.ts
+++ b/src/generators/shared/utils/getIntro.ts
@@ -1,5 +1,5 @@
 import deindent from '../../../utils/deindent.js';
-import getGlobals from './getGlobals';
+import getGlobals from './getGlobals.ts';
 
 export default function getIntro ( format: string, options, imports ) {
 	if ( format === 'es' ) return '';
diff --git a/src/generators/shared/utils/getOutro.ts b/src/generators/shared/utils/getOutro.ts
index b1cac890a3..73e531d607 100644
--- a/src/generators/shared/utils/getOutro.ts
+++ b/src/generators/shared/utils/getOutro.ts
@@ -1,4 +1,4 @@
-import getGlobals from './getGlobals';
+import getGlobals from './getGlobals.ts';
 
 export default function getOutro ( format: string, name: string, options, imports ) {
 	if ( format === 'es' ) {
diff --git a/src/index.ts b/src/index.ts
index 0c53e1840b..3b1b0a51d0 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,7 @@
-import parse from './parse/index';
-import validate from './validate/index';
-import generate from './generators/dom/index';
-import generateSSR from './generators/server-side-rendering/index';
+import parse from './parse/index.ts';
+import validate from './validate/index.ts';
+import generate from './generators/dom/index.ts';
+import generateSSR from './generators/server-side-rendering/index.ts';
 import { assign } from './shared/index.js';
 import { version } from '../package.json';
 
diff --git a/src/parse/index.ts b/src/parse/index.ts
index 5b73cfc1d2..982afb7110 100644
--- a/src/parse/index.ts
+++ b/src/parse/index.ts
@@ -1,9 +1,9 @@
 import { locate } from 'locate-character';
-import fragment from './state/fragment';
-import { whitespace } from '../utils/patterns';
-import { trimStart, trimEnd } from '../utils/trim';
-import getCodeFrame from '../utils/getCodeFrame';
-import hash from './utils/hash';
+import fragment from './state/fragment.ts';
+import { whitespace } from '../utils/patterns.ts';
+import { trimStart, trimEnd } from '../utils/trim.ts';
+import getCodeFrame from '../utils/getCodeFrame.ts';
+import hash from './utils/hash.ts';
 
 function ParseError ( message, template, index, filename ) {
 	const { line, column } = locate( template, index );
diff --git a/src/parse/state/fragment.ts b/src/parse/state/fragment.ts
index 7bce4c923b..af9d7eb861 100644
--- a/src/parse/state/fragment.ts
+++ b/src/parse/state/fragment.ts
@@ -1,6 +1,6 @@
-import tag from './tag';
-import mustache from './mustache';
-import text from './text';
+import tag from './tag.ts';
+import mustache from './mustache.ts';
+import text from './text.ts';
 
 export default function fragment ( parser ) {
 	if ( parser.match( '<' ) ) {
diff --git a/src/parse/state/mustache.ts b/src/parse/state/mustache.ts
index 1f1b6dcf8d..97781cc9c3 100644
--- a/src/parse/state/mustache.ts
+++ b/src/parse/state/mustache.ts
@@ -1,6 +1,6 @@
-import readExpression from '../read/expression';
-import { whitespace } from '../../utils/patterns';
-import { trimStart, trimEnd } from '../../utils/trim';
+import readExpression from '../read/expression.ts';
+import { whitespace } from '../../utils/patterns.ts';
+import { trimStart, trimEnd } from '../../utils/trim.ts';
 
 const validIdentifier = /[a-zA-Z_$][a-zA-Z0-9_$]*/;
 
diff --git a/src/parse/state/tag.ts b/src/parse/state/tag.ts
index 179210d02c..c492d99bc1 100644
--- a/src/parse/state/tag.ts
+++ b/src/parse/state/tag.ts
@@ -1,10 +1,10 @@
-import readExpression from '../read/expression';
-import readScript from '../read/script';
-import readStyle from '../read/style';
-import { readEventHandlerDirective, readBindingDirective, readTransitionDirective } from '../read/directives';
-import { trimStart, trimEnd } from '../../utils/trim';
-import { decodeCharacterReferences } from '../utils/html';
-import isVoidElementName from '../../utils/isVoidElementName';
+import readExpression from '../read/expression.ts';
+import readScript from '../read/script.ts';
+import readStyle from '../read/style.ts';
+import { readEventHandlerDirective, readBindingDirective, readTransitionDirective } from '../read/directives.ts';
+import { trimStart, trimEnd } from '../../utils/trim.ts';
+import { decodeCharacterReferences } from '../utils/html.ts';
+import isVoidElementName from '../../utils/isVoidElementName.ts';
 
 const validTagName = /^\!?[a-zA-Z]{1,}:?[a-zA-Z0-9\-]*/;
 const invalidUnquotedAttributeCharacters = /[\s"'=<>\/`]/;
diff --git a/src/parse/state/text.ts b/src/parse/state/text.ts
index 6d976c6cbb..eec33ac996 100644
--- a/src/parse/state/text.ts
+++ b/src/parse/state/text.ts
@@ -1,4 +1,4 @@
-import { decodeCharacterReferences } from '../utils/html';
+import { decodeCharacterReferences } from '../utils/html.ts';
 
 export default function text ( parser ) {
 	const start = parser.index;
diff --git a/src/parse/utils/html.ts b/src/parse/utils/html.ts
index 4b06db0723..8329909ed0 100644
--- a/src/parse/utils/html.ts
+++ b/src/parse/utils/html.ts
@@ -1,4 +1,4 @@
-import htmlEntities from './entities';
+import htmlEntities from './entities.ts';
 
 const windows1252 = [ 8364, 129, 8218, 402, 8222, 8230, 8224, 8225, 710, 8240, 352, 8249, 338, 141, 381, 143, 144, 8216, 8217, 8220, 8221, 8226, 8211, 8212, 732, 8482, 353, 8250, 339, 157, 382, 376 ];
 const entityPattern = new RegExp( `&(#?(?:x[\\w\\d]+|\\d+|${Object.keys( htmlEntities ).join( '|' )}));?`, 'g' );
diff --git a/src/utils/__test__.ts b/src/utils/__test__.ts
index 99e90bb76a..d97990aec3 100644
--- a/src/utils/__test__.ts
+++ b/src/utils/__test__.ts
@@ -1,6 +1,6 @@
 import * as assert from 'assert';
 import deindent from './deindent.js';
-import CodeBuilder from './CodeBuilder';
+import CodeBuilder from './CodeBuilder.ts';
 
 describe( 'deindent', () => {
 	it( 'deindents a simple string', () => {
diff --git a/src/utils/trim.ts b/src/utils/trim.ts
index 3c339a159b..56e403c246 100644
--- a/src/utils/trim.ts
+++ b/src/utils/trim.ts
@@ -1,4 +1,4 @@
-import { whitespace } from './patterns';
+import { whitespace } from './patterns.ts';
 
 export function trimStart ( str: string ) {
 	let i = 0;
diff --git a/src/validate/html/index.ts b/src/validate/html/index.ts
index 53076c69a3..fe5edbc489 100644
--- a/src/validate/html/index.ts
+++ b/src/validate/html/index.ts
@@ -1,6 +1,6 @@
-import * as namespaces from '../../utils/namespaces';
-import validateElement from './validateElement';
-import validateWindow from './validateWindow';
+import * as namespaces from '../../utils/namespaces.ts';
+import validateElement from './validateElement.ts';
+import validateWindow from './validateWindow.ts';
 
 const svg = /^(?:altGlyph|altGlyphDef|altGlyphItem|animate|animateColor|animateMotion|animateTransform|circle|clipPath|color-profile|cursor|defs|desc|discard|ellipse|feBlend|feColorMatrix|feComponentTransfer|feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|feDistantLight|feDropShadow|feFlood|feFuncA|feFuncB|feFuncG|feFuncR|feGaussianBlur|feImage|feMerge|feMergeNode|feMorphology|feOffset|fePointLight|feSpecularLighting|feSpotLight|feTile|feTurbulence|filter|font|font-face|font-face-format|font-face-name|font-face-src|font-face-uri|foreignObject|g|glyph|glyphRef|hatch|hatchpath|hkern|image|line|linearGradient|marker|mask|mesh|meshgradient|meshpatch|meshrow|metadata|missing-glyph|mpath|path|pattern|polygon|polyline|radialGradient|rect|set|solidcolor|stop|switch|symbol|text|textPath|title|tref|tspan|unknown|use|view|vkern)$/;
 
diff --git a/src/validate/html/validateElement.ts b/src/validate/html/validateElement.ts
index bc0ba07f12..8d902b1af3 100644
--- a/src/validate/html/validateElement.ts
+++ b/src/validate/html/validateElement.ts
@@ -1,4 +1,4 @@
-import validateEventHandler from './validateEventHandler';
+import validateEventHandler from './validateEventHandler.ts';
 
 export default function validateElement ( validator, node ) {
 	const isComponent = node.name === ':Self' || validator.components.has( node.name );
diff --git a/src/validate/html/validateEventHandler.ts b/src/validate/html/validateEventHandler.ts
index 56297f4ad1..17bcca3c20 100644
--- a/src/validate/html/validateEventHandler.ts
+++ b/src/validate/html/validateEventHandler.ts
@@ -1,5 +1,5 @@
-import flattenReference from '../../utils/flattenReference';
-import list from '../utils/list';
+import flattenReference from '../../utils/flattenReference.ts';
+import list from '../utils/list.ts';
 
 const validBuiltins = new Set([
 	'set',
diff --git a/src/validate/html/validateWindow.ts b/src/validate/html/validateWindow.ts
index bda75dd773..c9fd9996ad 100644
--- a/src/validate/html/validateWindow.ts
+++ b/src/validate/html/validateWindow.ts
@@ -1,7 +1,7 @@
-import flattenReference from '../../utils/flattenReference';
-import fuzzymatch from '../utils/fuzzymatch';
-import list from '../utils/list';
-import validateEventHandler from './validateEventHandler';
+import flattenReference from '../../utils/flattenReference.ts';
+import fuzzymatch from '../utils/fuzzymatch.ts';
+import list from '../utils/list.ts';
+import validateEventHandler from './validateEventHandler.ts';
 
 const validBindings = [
 	'innerWidth',
diff --git a/src/validate/index.ts b/src/validate/index.ts
index d9240b12eb..5e219e644e 100644
--- a/src/validate/index.ts
+++ b/src/validate/index.ts
@@ -1,7 +1,7 @@
-import validateJs from './js/index';
-import validateHtml from './html/index';
+import validateJs from './js/index.ts';
+import validateHtml from './html/index.ts';
 import { getLocator } from 'locate-character';
-import getCodeFrame from '../utils/getCodeFrame';
+import getCodeFrame from '../utils/getCodeFrame.ts';
 
 export default function validate ( parsed, source, { onerror, onwarn, name, filename } ) {
 	const locator = getLocator( source );
diff --git a/src/validate/js/index.ts b/src/validate/js/index.ts
index 9ccba4b944..fa0bde7d97 100644
--- a/src/validate/js/index.ts
+++ b/src/validate/js/index.ts
@@ -1,8 +1,8 @@
-import propValidators from './propValidators/index';
-import fuzzymatch from '../utils/fuzzymatch';
-import checkForDupes from './utils/checkForDupes';
-import checkForComputedKeys from './utils/checkForComputedKeys';
-import namespaces from '../../utils/namespaces';
+import propValidators from './propValidators/index.ts';
+import fuzzymatch from '../utils/fuzzymatch.ts';
+import checkForDupes from './utils/checkForDupes.ts';
+import checkForComputedKeys from './utils/checkForComputedKeys.ts';
+import namespaces from '../../utils/namespaces.ts';
 
 const validPropList = Object.keys( propValidators );
 
diff --git a/src/validate/js/propValidators/components.ts b/src/validate/js/propValidators/components.ts
index 78e9a1c57c..4a7ecc5de5 100644
--- a/src/validate/js/propValidators/components.ts
+++ b/src/validate/js/propValidators/components.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes';
-import checkForComputedKeys from '../utils/checkForComputedKeys';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 export default function components ( validator, prop ) {
 	if ( prop.value.type !== 'ObjectExpression' ) {
diff --git a/src/validate/js/propValidators/computed.ts b/src/validate/js/propValidators/computed.ts
index 50e4a5c67f..e02f7e5006 100644
--- a/src/validate/js/propValidators/computed.ts
+++ b/src/validate/js/propValidators/computed.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes';
-import checkForComputedKeys from '../utils/checkForComputedKeys';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 const isFunctionExpression = new Set( [ 'FunctionExpression', 'ArrowFunctionExpression' ] );
 
diff --git a/src/validate/js/propValidators/events.ts b/src/validate/js/propValidators/events.ts
index 2cf8ed10b7..efcef44e17 100644
--- a/src/validate/js/propValidators/events.ts
+++ b/src/validate/js/propValidators/events.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes';
-import checkForComputedKeys from '../utils/checkForComputedKeys';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 export default function events ( validator, prop ) {
 	if ( prop.value.type !== 'ObjectExpression' ) {
diff --git a/src/validate/js/propValidators/helpers.ts b/src/validate/js/propValidators/helpers.ts
index 09cae85189..070ba12acb 100644
--- a/src/validate/js/propValidators/helpers.ts
+++ b/src/validate/js/propValidators/helpers.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes';
-import checkForComputedKeys from '../utils/checkForComputedKeys';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 import { walk } from 'estree-walker';
 
 export default function helpers ( validator, prop ) {
diff --git a/src/validate/js/propValidators/index.ts b/src/validate/js/propValidators/index.ts
index e2e446407a..ffbf9306c8 100644
--- a/src/validate/js/propValidators/index.ts
+++ b/src/validate/js/propValidators/index.ts
@@ -1,15 +1,15 @@
-import data from './data';
-import computed from './computed';
-import oncreate from './oncreate';
-import ondestroy from './ondestroy';
-import onrender from './onrender';
-import onteardown from './onteardown';
-import helpers from './helpers';
-import methods from './methods';
-import components from './components';
-import events from './events';
-import namespace from './namespace';
-import transitions from './transitions';
+import data from './data.ts';
+import computed from './computed.ts';
+import oncreate from './oncreate.ts';
+import ondestroy from './ondestroy.ts';
+import onrender from './onrender.ts';
+import onteardown from './onteardown.ts';
+import helpers from './helpers.ts';
+import methods from './methods.ts';
+import components from './components.ts';
+import events from './events.ts';
+import namespace from './namespace.ts';
+import transitions from './transitions.ts';
 
 export default {
 	data,
diff --git a/src/validate/js/propValidators/methods.ts b/src/validate/js/propValidators/methods.ts
index bf12f921b5..0de3fa8fad 100644
--- a/src/validate/js/propValidators/methods.ts
+++ b/src/validate/js/propValidators/methods.ts
@@ -1,7 +1,7 @@
-import checkForAccessors from '../utils/checkForAccessors';
-import checkForDupes from '../utils/checkForDupes';
-import checkForComputedKeys from '../utils/checkForComputedKeys';
-import usesThisOrArguments from '../utils/usesThisOrArguments';
+import checkForAccessors from '../utils/checkForAccessors.ts';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
+import usesThisOrArguments from '../utils/usesThisOrArguments.ts';
 
 const builtin = new Set( [ 'set', 'get', 'on', 'fire', 'observe', 'destroy' ] );
 
diff --git a/src/validate/js/propValidators/namespace.ts b/src/validate/js/propValidators/namespace.ts
index a551b3f3c9..b96e2361b5 100644
--- a/src/validate/js/propValidators/namespace.ts
+++ b/src/validate/js/propValidators/namespace.ts
@@ -1,5 +1,5 @@
-import * as namespaces from '../../../utils/namespaces';
-import fuzzymatch from '../../utils/fuzzymatch';
+import * as namespaces from '../../../utils/namespaces.ts';
+import fuzzymatch from '../../utils/fuzzymatch.ts';
 
 const valid = new Set( namespaces.validNamespaces );
 
diff --git a/src/validate/js/propValidators/oncreate.ts b/src/validate/js/propValidators/oncreate.ts
index 6481a53064..55ee524b30 100644
--- a/src/validate/js/propValidators/oncreate.ts
+++ b/src/validate/js/propValidators/oncreate.ts
@@ -1,4 +1,4 @@
-import usesThisOrArguments from '../utils/usesThisOrArguments';
+import usesThisOrArguments from '../utils/usesThisOrArguments.ts';
 
 export default function oncreate ( validator, prop ) {
 	if ( prop.value.type === 'ArrowFunctionExpression' ) {
diff --git a/src/validate/js/propValidators/ondestroy.ts b/src/validate/js/propValidators/ondestroy.ts
index c65fa78d98..3dae006f1b 100644
--- a/src/validate/js/propValidators/ondestroy.ts
+++ b/src/validate/js/propValidators/ondestroy.ts
@@ -1,4 +1,4 @@
-import usesThisOrArguments from '../utils/usesThisOrArguments';
+import usesThisOrArguments from '../utils/usesThisOrArguments.ts';
 
 export default function ondestroy ( validator, prop ) {
 	if ( prop.value.type === 'ArrowFunctionExpression' ) {
diff --git a/src/validate/js/propValidators/onrender.ts b/src/validate/js/propValidators/onrender.ts
index d6baa00b02..49530326e0 100644
--- a/src/validate/js/propValidators/onrender.ts
+++ b/src/validate/js/propValidators/onrender.ts
@@ -1,4 +1,4 @@
-import oncreate from './oncreate';
+import oncreate from './oncreate.ts';
 
 export default function onrender ( validator, prop ) {
 	validator.warn( `'onrender' has been deprecated in favour of 'oncreate', and will cause an error in Svelte 2.x`, prop.start );
diff --git a/src/validate/js/propValidators/onteardown.ts b/src/validate/js/propValidators/onteardown.ts
index fe685d2085..ec7cfb9bc3 100644
--- a/src/validate/js/propValidators/onteardown.ts
+++ b/src/validate/js/propValidators/onteardown.ts
@@ -1,4 +1,4 @@
-import ondestroy from './ondestroy';
+import ondestroy from './ondestroy.ts';
 
 export default function onteardown ( validator, prop ) {
 	validator.warn( `'onteardown' has been deprecated in favour of 'ondestroy', and will cause an error in Svelte 2.x`, prop.start );
diff --git a/src/validate/js/propValidators/transitions.ts b/src/validate/js/propValidators/transitions.ts
index e4de4e4bb2..5287a1f803 100644
--- a/src/validate/js/propValidators/transitions.ts
+++ b/src/validate/js/propValidators/transitions.ts
@@ -1,5 +1,5 @@
-import checkForDupes from '../utils/checkForDupes';
-import checkForComputedKeys from '../utils/checkForComputedKeys';
+import checkForDupes from '../utils/checkForDupes.ts';
+import checkForComputedKeys from '../utils/checkForComputedKeys.ts';
 
 export default function transitions ( validator, prop ) {
 	if ( prop.value.type !== 'ObjectExpression' ) {
diff --git a/src/validate/js/utils/usesThisOrArguments.ts b/src/validate/js/utils/usesThisOrArguments.ts
index 82a0497333..dfc2044c6d 100644
--- a/src/validate/js/utils/usesThisOrArguments.ts
+++ b/src/validate/js/utils/usesThisOrArguments.ts
@@ -1,5 +1,5 @@
 import { walk } from 'estree-walker';
-import isReference from '../../../utils/isReference';
+import isReference from '../../../utils/isReference.ts';
 
 export default function usesThisOrArguments ( node ) {
 	let result = false;
diff --git a/src/validate/utils/fuzzymatch.ts b/src/validate/utils/fuzzymatch.ts
index 756af6b94e..62bc770f87 100644
--- a/src/validate/utils/fuzzymatch.ts
+++ b/src/validate/utils/fuzzymatch.ts
@@ -1,4 +1,4 @@
-import FuzzySet from './FuzzySet';
+import FuzzySet from './FuzzySet.ts';
 
 export default function fuzzymatch ( name, names ) {
 	const set = new FuzzySet( names );
diff --git a/tsconfig.json b/tsconfig.json
index 080fbe6644..f81940868c 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -10,7 +10,7 @@
     },
     "target": "ES5",
     "include": [
-        "src/**/*"
+        "src"
     ],
     "exclude": [
         "node_modules"