diff --git a/css/ui.css b/css/ui.css
index 1a2ad748..a8fe0a76 100644
--- a/css/ui.css
+++ b/css/ui.css
@@ -812,4 +812,7 @@ div.scripting-cell button:hover {
 }
 div.scripting-cell button.scripting-enabled {
   background-color: #339999;
+}
+.dialog-help {
+  color: #6666ff;
 }
\ No newline at end of file
diff --git a/doc/platforms.md b/doc/platforms.md
index 5e8bd709..ae465c89 100644
--- a/doc/platforms.md
+++ b/doc/platforms.md
@@ -15,7 +15,7 @@ Mandatory functions:
 These are for the compiler/editor:
 ~~~
   getToolForFilename(s:string) : string;
-  getDefaultExtension() : string;
+  getDefaultExtensions() : string[];
   getPresets() : Preset[];
 ~~~
 
@@ -205,7 +205,7 @@ class ColecoVisionMAMEPlatform extends BaseMAMEPlatform implements Platform {
 
   getPresets() { return ColecoVision_PRESETS; }
   getToolForFilename = getToolForFilename_z80;
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [".c", ".ns", ".s", ".scc", ".sgb", ".z", ".wiz"]; }
 }
 ~~~
 
diff --git a/src/common/baseplatform.ts b/src/common/baseplatform.ts
index d41e34aa..2fced0af 100644
--- a/src/common/baseplatform.ts
+++ b/src/common/baseplatform.ts
@@ -81,7 +81,7 @@ export interface Platform {
   reset(): void;
   isRunning(): boolean;
   getToolForFilename(s: string): string;
-  getDefaultExtension(): string;
+  getDefaultExtensions(): string[];
   getPresets?(): Preset[];
   pause(): void;
   resume(): void;
@@ -480,7 +480,7 @@ export abstract class Base6502Platform extends BaseDebugPlatform {
     return disassemble6502(pc, read(pc), read(pc + 1), read(pc + 2));
   }
   getToolForFilename = getToolForFilename_6502;
-  getDefaultExtension() { return ".a"; };
+  getDefaultExtensions() { return [".c", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"]; };
 
   getDebugCategories() {
     return ['CPU', 'ZPRAM', 'Stack'];
@@ -600,7 +600,7 @@ export abstract class BaseZ80Platform extends BaseDebugPlatform {
   }
 
   getToolForFilename = getToolForFilename_z80;
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [".c", ".ns", ".s", ".scc", ".sgb", ".z", ".wiz"]; };
   // TODO: Z80 opcode metadata
   //this.getOpcodeMetadata = function() { }
 
@@ -677,7 +677,7 @@ export abstract class Base6809Platform extends BaseZ80Platform {
     // TODO: don't create new CPU
     return Object.create(CPU6809()).disasm(read(pc), read(pc + 1), read(pc + 2), read(pc + 3), read(pc + 4), pc);
   }
-  getDefaultExtension(): string { return ".asm"; };
+  getDefaultExtensions() { return [".c", ".lwasm", ".xasm"]; };
   //this.getOpcodeMetadata = function() { }
   getToolForFilename = getToolForFilename_6809;
   getDebugCategories() {
@@ -789,7 +789,7 @@ export abstract class BaseMachinePlatform<T extends Machine> extends BaseDebugPl
 
   abstract newMachine(): T;
   abstract getToolForFilename(s: string): string;
-  abstract getDefaultExtension(): string;
+  abstract getDefaultExtensions(): string[];
   abstract getPresets(): Preset[];
 
   constructor(mainElement: HTMLElement) {
@@ -979,6 +979,7 @@ export abstract class Base6502MachinePlatform<T extends Machine> extends BaseMac
 
   getOpcodeMetadata = getOpcodeMetadata_6502;
   getToolForFilename(fn) { return getToolForFilename_6502(fn); }
+  getDefaultExtensions() { return [".c", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"]; }
 
   disassemble(pc: number, read: (addr: number) => number): DisasmLine {
     return disassemble6502(pc, read(pc), read(pc + 1), read(pc + 2));
@@ -1003,6 +1004,7 @@ export abstract class BaseZ80MachinePlatform<T extends Machine> extends BaseMach
 
   //getOpcodeMetadata     = getOpcodeMetadata_z80;
   getToolForFilename = getToolForFilename_z80;
+  getDefaultExtensions() { return [".c", ".ns", ".s", ".scc", ".sgb", ".z", ".wiz"]; }
 
   getDebugCategories() {
     if (isDebuggable(this.machine))
@@ -1032,6 +1034,7 @@ export abstract class BaseZ80MachinePlatform<T extends Machine> extends BaseMach
 export abstract class Base6809MachinePlatform<T extends Machine> extends BaseMachinePlatform<T> {
 
   getToolForFilename = getToolForFilename_6809;
+  getDefaultExtensions() { return [".c", ".lwasm", ".xasm"]; }
 
   getDebugCategories() {
     if (isDebuggable(this.machine))
diff --git a/src/ide/ui.ts b/src/ide/ui.ts
index 30d4c923..012e9501 100644
--- a/src/ide/ui.ts
+++ b/src/ide/ui.ts
@@ -495,14 +495,18 @@ function checkEnteredFilename(fn: string): boolean {
 
 function _createNewFile(e) {
   // TODO: support spaces
+  var extensions = platform.getDefaultExtensions();
   bootbox.prompt({
-    title: "Enter the name of your new main source file.",
-    placeholder: "newfile" + platform.getDefaultExtension(),
+    title: "Enter the name of your new main source file.<br><br>" +
+      "<span class='dialog-help'>" +
+      (extensions.length > 1 ? extensions.join(" ") : "") +
+      "</span>",
+    placeholder: "newfile" + extensions[0],
     callback: (filename) => {
       if (filename && filename.trim().length > 0) {
         if (!checkEnteredFilename(filename)) return;
         if (filename.indexOf(".") < 0) {
-          filename += platform.getDefaultExtension();
+          filename += extensions[0];
         }
         var path = filename;
         gaEvent('workspace', 'file', 'new');
diff --git a/src/platform/apple2.ts b/src/platform/apple2.ts
index 74af678f..ef6e5273 100644
--- a/src/platform/apple2.ts
+++ b/src/platform/apple2.ts
@@ -47,7 +47,7 @@ class Apple2MAMEPlatform extends BaseMAME6502Platform implements Platform {
   }
 
   getOpcodeMetadata = getOpcodeMetadata_6502;
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [".c", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"]; }
   getToolForFilename = getToolForFilename_6502;
 
   getPresets() { return APPLE2_PRESETS; }
@@ -64,7 +64,7 @@ class NewApple2Platform extends Base6502MachinePlatform<AppleII> implements Plat
 
   newMachine() { return new AppleII(); }
   getPresets() { return APPLE2_PRESETS; }
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [...super.getDefaultExtensions(), ".lnk"]; }
   readAddress(a) { return this.machine.readConst(a); }
   // TODO loadBIOS(bios)	{ this.machine.loadBIOS(a); }
   getMemoryMap = function () {
diff --git a/src/platform/arm32.ts b/src/platform/arm32.ts
index 4b53c5ca..af9d0b56 100644
--- a/src/platform/arm32.ts
+++ b/src/platform/arm32.ts
@@ -43,7 +43,7 @@ export abstract class BaseARMMachinePlatform<T extends Machine> extends BaseMach
       return "armtcc";
     }
     getPresets()          { return ARM32_PRESETS; }
-    getDefaultExtension() { return ".c"; };
+    getDefaultExtensions() { return [".c", ".armips", ".vasm"]; }
   }
   
 class ARM32Platform extends BaseARMMachinePlatform<ARM32Machine> implements Platform {
diff --git a/src/platform/astrocade.ts b/src/platform/astrocade.ts
index 51f9c0fb..9f99a99a 100644
--- a/src/platform/astrocade.ts
+++ b/src/platform/astrocade.ts
@@ -34,7 +34,6 @@ class BallyAstrocadePlatform extends BaseZ80MachinePlatform<BallyAstrocade> impl
 
   newMachine()          { return new BallyAstrocade(false); }
   getPresets()          { return ASTROCADE_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.read(a); }
   getMemoryMap = function() { return { main:[
       {name:'BIOS',start:0x0,size:0x2000,type:'rom'},
diff --git a/src/platform/atari7800.ts b/src/platform/atari7800.ts
index 11160c7a..41e99e56 100644
--- a/src/platform/atari7800.ts
+++ b/src/platform/atari7800.ts
@@ -19,7 +19,7 @@ class Atari7800Platform extends Base6502MachinePlatform<Atari7800> implements Pl
 
   newMachine()          { return new Atari7800(); }
   getPresets()          { return Atari7800_PRESETS; }
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [...super.getDefaultExtensions(), ".cc7800"]; }
   readAddress(a)        { return this.machine.readConst(a); }
   // TODO loadBIOS(bios)	{ this.machine.loadBIOS(a); }
   getMemoryMap = function() { return { main:[
diff --git a/src/platform/atari8.ts b/src/platform/atari8.ts
index aca7dddb..516862e9 100644
--- a/src/platform/atari8.ts
+++ b/src/platform/atari8.ts
@@ -43,7 +43,7 @@ function getToolForFilename_Atari8(fn:string) {
 class Atari800Platform extends Base6502MachinePlatform<Atari800> {
   newMachine()          { return new Atari800(); }
   getPresets()          { return Atari800_PRESETS; }
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [...super.getDefaultExtensions(), ".bas"]; }
   getToolForFilename = getToolForFilename_Atari8;
   readAddress(a)        { return this.machine.readConst(a); }
   getMemoryMap()        { return Atari800_MemoryMap; }
@@ -83,7 +83,7 @@ abstract class Atari8MAMEPlatform extends BaseMAME6502Platform {
   getPresets() { return Atari8_PRESETS; }
   getToolForFilename = getToolForFilename_Atari8;
   getOpcodeMetadata = getOpcodeMetadata_6502;
-  getDefaultExtension() { return ".asm"; };
+  getDefaultExtensions() { return [".c", ".bas", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"]; }
   showHelp = atari8_showHelp;
 }
 
diff --git a/src/platform/basic.ts b/src/platform/basic.ts
index 0fab306a..c2180af3 100644
--- a/src/platform/basic.ts
+++ b/src/platform/basic.ts
@@ -163,7 +163,7 @@ class BASICPlatform implements Platform {
 
     isBlocked() { return this.tty.waitingfor != null || this.runtime.exited; } // is blocked for input?
     isRunning() { return this.timer.isRunning(); }
-    getDefaultExtension() { return ".bas"; }
+    getDefaultExtensions() { return [".bas"]; }
     getToolForFilename() { return "basic"; }
     getPresets() { return BASIC_PRESETS; }
 
diff --git a/src/platform/c64.ts b/src/platform/c64.ts
index 8449c67d..d72ceefe 100644
--- a/src/platform/c64.ts
+++ b/src/platform/c64.ts
@@ -69,7 +69,6 @@ class C64WASMPlatform extends Base6502MachinePlatform<C64_WASMMachine> implement
   newMachine()          { return new C64_WASMMachine('c64'); }
 
   getPresets()          { return C64_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.readConst(a); }
   getMemoryMap()        { return C64_MEMORY_MAP; }
   showHelp()            { return "https://8bitworkshop.com/docs/platforms/c64/" }
@@ -87,7 +86,7 @@ abstract class C64MAMEPlatform extends BaseMAME6502Platform {
   getPresets() { return C64_PRESETS; }
   getToolForFilename = getToolForFilename_6502;
   getOpcodeMetadata = getOpcodeMetadata_6502;
-  getDefaultExtension() { return ".c"; }
+  getDefaultExtensions() { return [".c", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"]; }
   loadROM(title, data) {
     if (!this.started) {
       this.startModule(this.mainElement, {
diff --git a/src/platform/coleco.ts b/src/platform/coleco.ts
index eaaf9bd4..618925cf 100644
--- a/src/platform/coleco.ts
+++ b/src/platform/coleco.ts
@@ -25,7 +25,6 @@ class ColecoVisionPlatform extends BaseZ80MachinePlatform<ColecoVision> implemen
 
   newMachine()          { return new ColecoVision(); }
   getPresets()          { return ColecoVision_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.read(a); }
   readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
   // TODO loadBIOS(bios)	{ this.machine.loadBIOS(a); }
@@ -65,7 +64,7 @@ class ColecoVisionMAMEPlatform extends BaseMAMEZ80Platform implements Platform {
   getPresets() { return ColecoVision_PRESETS; }
 
   getToolForFilename = getToolForFilename_z80;
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [".c", ".ns", ".s", ".scc", ".sgb", ".z", ".wiz"]; }
 }
 
 
diff --git a/src/platform/cpc.ts b/src/platform/cpc.ts
index 34687e78..ca1aa50b 100644
--- a/src/platform/cpc.ts
+++ b/src/platform/cpc.ts
@@ -27,7 +27,6 @@ class CPCWASMPlatform extends BaseZ80MachinePlatform<CPC_WASMMachine> implements
   newMachine()          { return new CPC_WASMMachine('cpc'); }
 
   getPresets()          { return CPC_PRESETS; }
-  getDefaultExtension() { return ".asm"; };
   readAddress(a)        { return this.machine.readConst(a); }
   getMemoryMap()        { return CPC_MEMORY_MAP; }
   showHelp() {
diff --git a/src/platform/devel.ts b/src/platform/devel.ts
index fc3cce33..3776eb8c 100644
--- a/src/platform/devel.ts
+++ b/src/platform/devel.ts
@@ -167,7 +167,6 @@ class Devel6502Platform extends Base6502MachinePlatform<Devel6502> implements Pl
 
   newMachine()          { return new Devel6502(); }
   getPresets()          { return DEVEL_6502_PRESETS; }
-  getDefaultExtension() { return ".dasm"; };
   readAddress(a)        { return this.machine.readConst(a); }
 
   getMemoryMap = function() { return { main:[
diff --git a/src/platform/exidy.ts b/src/platform/exidy.ts
index 40dd8a46..b4746d8c 100644
--- a/src/platform/exidy.ts
+++ b/src/platform/exidy.ts
@@ -10,7 +10,6 @@ class ExidyUGBPlatform extends Base6502MachinePlatform<ExidyUGBv2> implements Pl
 
     newMachine() { return new ExidyUGBv2(); }
     getPresets() { return EXIDY_PRESETS; }
-    getDefaultExtension() { return ".dasm"; };
     readAddress(a) { return this.machine.readConst(a); }
 
     getMemoryMap() {
diff --git a/src/platform/galaxian.ts b/src/platform/galaxian.ts
index 43371c19..e9dd107c 100644
--- a/src/platform/galaxian.ts
+++ b/src/platform/galaxian.ts
@@ -13,7 +13,6 @@ class GalaxianPlatform extends BaseZ80MachinePlatform<GalaxianMachine> implement
 
   newMachine()          { return new GalaxianMachine(); }
   getPresets()          { return GALAXIAN_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.readConst(a); }
   readVRAMAddress(a)    { return (a < 0x800) ? this.machine.vram[a] : this.machine.oram[a-0x800]; }
   // TODO loadBIOS(bios)	{ this.machine.loadBIOS(a); }
diff --git a/src/platform/gb.ts b/src/platform/gb.ts
index df706938..cf83b403 100644
--- a/src/platform/gb.ts
+++ b/src/platform/gb.ts
@@ -1,4 +1,3 @@
-
 import { GameBoyMachine } from "../machine/gb";
 import { BaseMachinePlatform, cpuStateToLongString_SM83, getToolForFilename_z80, Platform, Preset, dumpStackToString, isDebuggable, EmuState, DisasmLine } from "../common/baseplatform";
 import { PLATFORMS } from "../common/emu";
@@ -13,7 +12,7 @@ class GameBoyPlatform extends BaseMachinePlatform<GameBoyMachine> implements Pla
 
   newMachine()          { return new GameBoyMachine(); }
   getPresets()          { return GB_PRESETS; }
-  getDefaultExtension() { return ".c"; }
+  getDefaultExtensions() { return [".c", ".ns", ".s", ".scc", ".sgb", ".z", ".wiz"]; }
   getToolForFilename    = getToolForFilename_z80;
   readAddress(a)        { return this.machine.read(a); }
   readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
@@ -72,4 +71,4 @@ class GameBoyPlatform extends BaseMachinePlatform<GameBoyMachine> implements Pla
 }
 
 PLATFORMS['gb'] = GameBoyPlatform;
-PLATFORMS['gameboy'] = GameBoyPlatform;
+PLATFORMS['gameboy'] = GameBoyPlatform;
\ No newline at end of file
diff --git a/src/platform/kim1.ts b/src/platform/kim1.ts
index a5bd01e6..55bd8583 100644
--- a/src/platform/kim1.ts
+++ b/src/platform/kim1.ts
@@ -12,7 +12,6 @@ class KIM1Platform extends Base6502MachinePlatform<KIM1> implements Platform {
 
   newMachine()          { return new KIM1(); }
   getPresets()          { return KIM1_PRESETS; }
-  getDefaultExtension() { return ".dasm"; };
   readAddress(a)        { return this.machine.readConst(a); }
 
   getMemoryMap = function() { return { main:[
diff --git a/src/platform/markdown.ts b/src/platform/markdown.ts
index bbf24f69..cf871bbe 100644
--- a/src/platform/markdown.ts
+++ b/src/platform/markdown.ts
@@ -33,8 +33,8 @@ class MarkdownPlatform implements Platform {
   getToolForFilename(fn : string) : string {
     return "markdown";
   }
-  getDefaultExtension() : string {
-    return ".md";
+  getDefaultExtensions() {
+    return [".md"];
   }
   getPresets() {
     return [
diff --git a/src/platform/msx.ts b/src/platform/msx.ts
index c49ce31b..d3c9176b 100644
--- a/src/platform/msx.ts
+++ b/src/platform/msx.ts
@@ -41,7 +41,7 @@ class MSXPlatform extends BaseZ80MachinePlatform<MSX1> implements Platform {
 
   newMachine()          { return new MSX1(); }
   getPresets()          { return MSX_BIOS_PRESETS; }
-  getDefaultExtension() { return ".c"; };
+
   readAddress(a)        { return this.machine.read(a); }
   readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
   getMemoryMap = function() { return { main:[
diff --git a/src/platform/mw8080bw.ts b/src/platform/mw8080bw.ts
index 3ea398c6..8aaa412b 100644
--- a/src/platform/mw8080bw.ts
+++ b/src/platform/mw8080bw.ts
@@ -16,7 +16,6 @@ class Midway8080BWPlatform extends BaseZ80MachinePlatform<Midway8080> implements
 
   newMachine()          { return new Midway8080(); }
   getPresets()          { return MW8080BW_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.read(a); }
   getMemoryMap = function() { return { main:[
       {name:'Frame Buffer',start:0x2400,size:7168,type:'ram'},
diff --git a/src/platform/nes.ts b/src/platform/nes.ts
index e03cda1d..d8ad6dad 100644
--- a/src/platform/nes.ts
+++ b/src/platform/nes.ts
@@ -268,7 +268,7 @@ class JSNESPlatform extends Base6502Platform implements Platform, Probeable {
   getOriginPC() {	// TODO: is actually NMI
     return (this.readAddress(0xfffa) | (this.readAddress(0xfffb) << 8)) & 0xffff;
   }
-  getDefaultExtension() { return ".c"; }
+  getDefaultExtensions() { return [...super.getDefaultExtensions(), ".nesasm"]; }
 
   getROMExtension() { return ".nes"; }
 
@@ -558,7 +558,7 @@ class NESMAMEPlatform extends BaseMAME6502Platform implements Platform {
   getPresets() { return JSNES_PRESETS; }
   getToolForFilename = getToolForFilename_6502;
   getOpcodeMetadata = getOpcodeMetadata_6502;
-  getDefaultExtension() { return ".c"; };
+  getDefaultExtensions() { return [".c", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"]; }
 
 }
 
diff --git a/src/platform/pce.ts b/src/platform/pce.ts
index 298391e4..5286a0eb 100644
--- a/src/platform/pce.ts
+++ b/src/platform/pce.ts
@@ -48,8 +48,8 @@ class PCEnginePlatform implements Platform {
     getToolForFilename(fn: string): string {
         return getToolForFilename_6502(fn);
     }
-    getDefaultExtension(): string {
-        return ".pce";
+    getDefaultExtensions() {
+        return [".c", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"];
     }
     readAddress(addr: number): number {
         return this.pce.Get(addr);
diff --git a/src/platform/sms.ts b/src/platform/sms.ts
index 5dcf5b27..7ebfb16f 100644
--- a/src/platform/sms.ts
+++ b/src/platform/sms.ts
@@ -32,7 +32,7 @@ class SG1000Platform extends BaseZ80MachinePlatform<SG1000> implements Platform
 
   newMachine()          { return new SG1000(); }
   getPresets()          { return SG1000_PRESETS; }
-  getDefaultExtension() { return ".c"; };
+
   readAddress(a)        { return this.machine.read(a); }
   readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
 }
@@ -41,7 +41,7 @@ class SMSPlatform extends BaseZ80MachinePlatform<SMS> implements Platform {
 
   newMachine()          { return new SMS(); }
   getPresets()          { return SMS_PRESETS; }
-  getDefaultExtension() { return ".c"; };
+
   readAddress(a)        { return this.machine.read(a); }
   readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
 }
@@ -50,7 +50,7 @@ class GameGearPlatform extends BaseZ80MachinePlatform<GameGear> implements Platf
 
   newMachine()          { return new GameGear(); }
   getPresets()          { return SMS_PRESETS; }
-  getDefaultExtension() { return ".c"; };
+
   readAddress(a)        { return this.machine.read(a); }
   readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
 }
diff --git a/src/platform/sound_williams.ts b/src/platform/sound_williams.ts
index 5b0cd3f7..33500b2b 100644
--- a/src/platform/sound_williams.ts
+++ b/src/platform/sound_williams.ts
@@ -113,7 +113,6 @@ export class WilliamsSoundPlatform extends BaseZ80MachinePlatform<WilliamsSound>
 
   newMachine()          { return new WilliamsSound(); }
   getPresets()          { return WILLIAMS_SOUND_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.read(a); }
 
 }
diff --git a/src/platform/vcs.ts b/src/platform/vcs.ts
index 190052f0..5c479db7 100644
--- a/src/platform/vcs.ts
+++ b/src/platform/vcs.ts
@@ -303,7 +303,7 @@ class VCSPlatform extends BasePlatform {
     return "\n" + dumpRAM(ram, 0x80, 0x80);
   }
   getToolForFilename = getToolForFilename_vcs;
-  getDefaultExtension() { return ".dasm"; }
+  getDefaultExtensions() { return [".c", ".bb", ".acme", ".ca65", ".dasm", ".cc2600", ".ecs", ".wiz"]; }
   getROMExtension() { return ".a26"; }
 
   getDebugCategories() {
@@ -480,7 +480,7 @@ class VCSMAMEPlatform extends BaseMAME6502Platform implements Platform {
   getPresets = function() { return VCS_PRESETS; }
 
   getToolForFilename = getToolForFilename_vcs;
-  getDefaultExtension() { return ".dasm"; }
+  getDefaultExtensions() { return [".c", ".bb", ".acme", ".ca65", ".dasm", ".cc2600", ".ecs", ".wiz"]; }
   getROMExtension() { return ".a26"; }
 
   getOriginPC = function() {
@@ -538,8 +538,8 @@ class VCSStellaPlatform implements Platform {
     return this.running;
   }
   getToolForFilename = getToolForFilename_vcs;
-  getDefaultExtension() { return ".dasm"; }
-  getROMExtension() { return ".a26"; }  
+  getDefaultExtensions() { return [".c", ".bb", ".acme", ".ca65", ".dasm", ".cc2600", ".ecs", ".wiz"]; }
+  getROMExtension() { return ".a26"; }
   getPresets() { return VCS_PRESETS }
 }
 
diff --git a/src/platform/verilog.ts b/src/platform/verilog.ts
index 6bf5dc03..8777e18a 100644
--- a/src/platform/verilog.ts
+++ b/src/platform/verilog.ts
@@ -718,7 +718,7 @@ var VerilogPlatform = function(mainElement, options) {
     else if (fn.endsWith(".ice")) return "silice";
     else return "verilator";
   }
-  getDefaultExtension() { return ".v"; };
+  getDefaultExtensions() { return [".v", ".asm", ".ice"]; }
 
   inspect(name:string) : string {
     if (!top) return;
diff --git a/src/platform/vic20.ts b/src/platform/vic20.ts
index 90768d0a..8531beae 100644
--- a/src/platform/vic20.ts
+++ b/src/platform/vic20.ts
@@ -32,7 +32,6 @@ class VIC20WASMPlatform extends Base6502MachinePlatform<VIC20_WASMMachine> imple
   newMachine()          { return new VIC20_WASMMachine('vic20'); }
 
   getPresets()          { return VIC20_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.readConst(a); }
   getMemoryMap()        { return VIC20_MEMORY_MAP; }
   showHelp() {
@@ -52,7 +51,7 @@ abstract class VIC20MAMEPlatform extends BaseMAME6502Platform {
   getPresets() { return VIC20_PRESETS; }
   getToolForFilename = getToolForFilename_6502;
   getOpcodeMetadata = getOpcodeMetadata_6502;
-  getDefaultExtension() { return ".c"; }
+  getDefaultExtensions() { return [".c", ".cpp", ".acme", ".ca65", ".dasm", ".ecs", ".wiz"]; }
   loadROM(title, data) {
     if (!this.started) {
       this.startModule(this.mainElement, {
diff --git a/src/platform/vicdual.ts b/src/platform/vicdual.ts
index 3ce42a2c..fcd606ac 100644
--- a/src/platform/vicdual.ts
+++ b/src/platform/vicdual.ts
@@ -18,7 +18,6 @@ class VicDualPlatform extends BaseZ80MachinePlatform<VicDual> implements Platfor
 
   newMachine()          { return new VicDual(); }
   getPresets()          { return VICDUAL_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.read(a); }
   // TODO loadBIOS(bios)	{ this.machine.loadBIOS(a); }
   getMemoryMap = function() { return { main:[
diff --git a/src/platform/williams.ts b/src/platform/williams.ts
index 1e6657a6..1800ebd3 100644
--- a/src/platform/williams.ts
+++ b/src/platform/williams.ts
@@ -479,7 +479,6 @@ class NewWilliamsPlatform extends Base6809MachinePlatform<WilliamsMachine> imple
 
   newMachine()          { return new WilliamsMachine(false); }
   getPresets()          { return WILLIAMS_PRESETS; }
-  getDefaultExtension() { return ".c"; };
   readAddress(a)        { return this.machine.readConst(a); }
   getMemoryMap() { 
     return { main:[
diff --git a/src/platform/x86.ts b/src/platform/x86.ts
index f6125296..1dcb5d0d 100644
--- a/src/platform/x86.ts
+++ b/src/platform/x86.ts
@@ -65,8 +65,8 @@ class X86PCPlatform implements Platform {
         if (s.endsWith(".c")) return "smlrc";
         return "yasm";
     }
-    getDefaultExtension(): string {
-        return ".asm";
+    getDefaultExtensions() {
+        return [".c", ".asm"];
     }
     getPresets() {
         return PC_PRESETS;
diff --git a/src/platform/zmachine.ts b/src/platform/zmachine.ts
index 7917193a..e9a1cd21 100644
--- a/src/platform/zmachine.ts
+++ b/src/platform/zmachine.ts
@@ -706,8 +706,8 @@ class ZmachinePlatform implements Platform {
     getToolForFilename(s: string): string {
         return "inform6";
     }
-    getDefaultExtension(): string {
-        return ".inf";
+    getDefaultExtensions() {
+        return [".inf"];
     }
     showHelp() {
         return "https://www.inform-fiction.org/manual/html/contents.html";
diff --git a/src/platform/zx.ts b/src/platform/zx.ts
index c6dffb5f..10b70360 100644
--- a/src/platform/zx.ts
+++ b/src/platform/zx.ts
@@ -24,7 +24,7 @@ class ZXWASMPlatform extends BaseZ80MachinePlatform<ZX_WASMMachine> implements P
   newMachine()          { return new ZX_WASMMachine('zx'); }
 
   getPresets()          { return ZX_PRESETS; }
-  getDefaultExtension() { return ".asm"; };
+
   readAddress(a)        { return this.machine.readConst(a); }
   getMemoryMap()        { return ZX_MEMORY_MAP; }
   showHelp() {
diff --git a/src/test/testanalysis.ts b/src/test/testanalysis.ts
index 576a2262..a6f90761 100644
--- a/src/test/testanalysis.ts
+++ b/src/test/testanalysis.ts
@@ -20,7 +20,7 @@ class Test6502Platform implements Platform {
     getToolForFilename(s: string): string {
         throw new Error("Method not implemented.");
     }
-    getDefaultExtension(): string {
+    getDefaultExtensions(): string[] {
         throw new Error("Method not implemented.");
     }
     pause(): void {
diff --git a/test/cli/testplatforms.js b/test/cli/testplatforms.js
index cc51cd83..e2df77e9 100644
--- a/test/cli/testplatforms.js
+++ b/test/cli/testplatforms.js
@@ -216,7 +216,10 @@ async function testPlatform(platid, romname, maxframes, callback) {
       if (dbgtree != null) JSON.stringify(dbgtree);
     }
     // misc
-    assert.ok(platform.getDefaultExtension().startsWith('.'));
+    var exts = platform.getDefaultExtensions();
+    assert.ok(Array.isArray(exts));
+    assert.ok(exts.length > 0);
+    exts.forEach(ext => assert.ok(ext.startsWith('.')));
     if (platform.getROMExtension) assert.ok(platform.getROMExtension().startsWith("."));
     // load state again
     platform.loadState(state3);