Portal: Prelude, as its name states it, is an unofficial prequel to the game Portal. Its story revolves around the pre-GlaDOS epoch, even before she was plugged in. At this time, test subjects were monitored by real Aperture Science employees, whose work was tedious, lengthy and repetitive. This is why they decided to build a great artificial intelligence that could both replace them in these difficult tasks, and also take responsibility for many other tasks within the complex and compete with Black Mesa's superiority. All employees of the Aperture Science complex are now eagerly awaiting GlaDOS. Maybe even a little too eagerly, as the upcoming events will tell... This game is totally free. It offers a bit more gameplay hours than the original Portal, with 8 chapters, 19 test chambers, 48 challenges, 6 advanced maps, a brand new storyline and more than 400 lines of english speech with dozens of subtitles translations.

Upload a file Report abuse Portal: Prelude 1.1.5 (archive version)
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All the files needed to make Portal: Prelude run. This version is exactly the same than the "installer" version except that it works better for Mac OS since it's a simple zip file. Valve ported their Source Engine under Mac OS without telling anyone and especially not me. Now I don't have the time, motivation and knowledge to port the game to Mac myself, but I can provide you with a zipped version and instructions on how to make it work. It's a bit tricky but so far it worked when we tested it on a Macbook. Instructions on how to make it work are available when you click here:

Extract to sourcemods folder. Open gameinfo.txt inside the Portalprelude folder. Underneath Filesystem there should be a section called FileSystem:

replace it with this:

		SteamAppId				400
			game+mod			|gameinfo_path|.
			platform			|gameinfo_path|.

			// We search VPK files before ordinary folders, because most files will be found in
			// VPK and we can avoid making thousands of file system calls to attempt to open files
			// in folders where they don't exist.  (Searching a VPK is much faster than making an operating
			// system call.)
			game_lv				portal/portal_lv.vpk
			game+mod			portal/portal_english.vpk
			game+mod			portal/portal_pak.vpk
			game				|all_source_engine_paths|hl2/hl2_textures.vpk
			game				|all_source_engine_paths|hl2/hl2_sound_vo_english.vpk
			game				|all_source_engine_paths|hl2/hl2_sound_misc.vpk
			game				|all_source_engine_paths|hl2/hl2_misc.vpk
			platform			|all_source_engine_paths|platform/platform_misc.vpk

			// Now search loose files.  We'll set the directory containing the gameinfo.txt file
			// as the first "mod" search path (after any user customizations).  This is also the one
			// that's used when writing to the "mod" path.
			mod+mod_write+default_write_path	|gameinfo_path|.

			// Add the mod directory as a game search path.  This is also where where writes
			// to the "game" path go.
			game+game_write			|gameinfo_path|.

			// Where the game's binaries are
			gamebin				portal/bin

			// Last, mount in shared Portal loose files
			game				|all_source_engine_paths|portal

			// Last, mount in shared HL2 loose files
			game				|all_source_engine_paths|hl2
			platform			|all_source_engine_paths|platform



I've been investigating with a mac-user friend for 4 hours what could be going wrong with Portal on Mac OS to prevent Portal: Prelude from running and the news are half bad and half good.

The bad news is that Valve lied to us (again) when they said the Mac version of Portal was a "native versions rather than emulation" and that "PC and Mac build at the same time, automatically, so the two platforms are perfectly in lock-step" [source]. The Mac version is very different than the PC version in the way that it partially drops the support for third party mods. I don't know if this was intentional and if they're aware of it, but it sucks bad. If you want to express to disappointment, you should directly email Valve's CEO and tell him: gaben@valvesoftware

The good news is that it's still possible to make Portal: Prelude run under Mac OS using a few extra steps I'm going to explain.


First, install Portal and Portal: Prelude. You should put Portal: Prelude content in the /Users//Documents/Steam Content/sourcemods/portal prelude folder. Watch out though, because they said this location was going to change soon. If you encounter a problem while unzipping Portal: Prelude it's because there is something wrong with the default Mac OS un-archiver. Using the unzip command-line tool works just great. I don't know what's wrong but I'll try to re-upload a version that was created under Mac OS for what it's worth.

Then problems arise. The Mac OS version seems to drop the support of the -game parameter and thus, the support of third party mods in an elegant manner. Also, it seems that it drops the support of spaces in folders, thus, "portal prelude" is not recognized anymore. What you have to do is to create a symbolic link in another location to make Portal aware that new content is available. For this, you have to open Terminal (using Finder for example) and type the following commands:

cd "/Users/[your Mac OS username]/Documents/Steam Content/[your Steam username]/portal/"
ln -s "../../sourcemods/portal prelude" portalprelude

This will tell Portal that new content is available next to him but not how to use it, this is the next step.

When this is done, restart Steam and Portal: Prelude should appear in you games list. Beware though, this shortcut won't work. Basically, as they dropped the support of third party mods, you'll have to tell Portal to use Portal: Prelude content instead of having another standalone game besides it. The way to do this is weird, but works.

  1. Open up your Steam games library
  2. Right click on "Portal" and click Properties
  3. Open up the "Set Launch Options" dialog
  4. Type this in the field: -game portalprelude -dev
  5. Launch Portal and it should launch Portal: Prelude instead

So far it looks like this method works at a 100%, I didn't play the whole game though but we had everything working from cutscenes, voices, subtitles, gameplay, and such. If you want to play Portal again, simply remove the -game portalprelude -dev from the launch properties.


Now on a more technical side, I'm totally unsure WHY the hell you have to launch the game in developer mode (-dev) for it to work, but we never managed to make it work without it. We are also sure there are probably ways to do this differently. We investigated a few things, like the open command of Mac OS combined with the command line options of Steam. Basically, we tried this:

open -a steam -applaunch 400 --args -game portalprelude -dev

It works perfectly, but only when Steam isn't already launched. Mac OS seem to catch the call and prevent it when Steam is already running. We don't know how we could bypass this. We also elaborated on the Steam Browser Protocol to make it launch Portal with Portal: Prelude content like this:

open steam://run/400 -game portalprelude -dev

But so far, the Steam Browser Protocol doesn't seem to be able to deal with parameters, so we gave up.

If you are knowledgeable enough, maybe you'll find a more elegant solution to this problem. We hate the current solution because it forces you to switch between Portal and Portal: Prelude and you can't have both working at the same time. If you do find a more elegant solution, please post it on our forums : Portalprelude.com

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Portal: Prelude 1.1.5 (archive version)
Post comment Comments
cW#Ravenblood May 21 2010, 9:08am says:

its awesome :3

+1 vote     reply to comment
hotdog2449 Jul 1 2010, 7:15am says:

yes, i like this new version

+2 votes     reply to comment
AmaroqDricaldari Apr 3 2011, 9:56pm replied:

Is it better than the previous version in anyway?

Also, will it repalce my Portal Files? Or am I not required to back up my Portal Files?

+1 vote     reply to comment
XSandeNX Jul 21 2013, 7:07pm replied:

No it wont.
It does nothing once you install it.
Besides letting you actually play it :D

+1 vote     reply to comment
CANDYKILLER05 Sep 10 2010, 1:45am says:

can you help me? i dont really get it. what do we need to do after downloading the file?

+1 vote     reply to comment
zombiemaster008 Oct 17 2010, 11:27am replied:

put it in your souremods folder

+1 vote     reply to comment
MODdJ Dec 3 2010, 3:28pm says:

What's up with the slow download?!

+2 votes     reply to comment
Guest Jun 16 2013, 3:53am replied:

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starstreakcomet Mar 28 2011, 10:00am says:

New terminal code for new location!

cd "/Users/[usrname]/Library/Application Support/Steam/SteamApps/[steam username]/portal/"

ln -s "../../sourcemods/portal prelude" portalprelude

Now to see if it works...

+1 vote     reply to comment
starstreakcomet Mar 28 2011, 10:16am says:

New code for new location!

cd "/Users/[usrname]/Library/Application Support/Steam/SteamApps/[steam username]/portal/"

ln -s "../../sourcemods/portal prelude" portalprelude

but when opening it through steam through portal, it's not working (black screen for indefinite amt of time) because it is missing something like background.vbg. Too busy to deal, any ideas?

+1 vote     reply to comment
pcformat2 Aug 23 2011, 2:24pm says:

kurwa do portal prelude jak diała na mac diała mac do pencie diałać na mac do pencie diałć na pc portal

0 votes     reply to comment
pcformat2 Aug 23 2011, 2:29pm says:

kurwa pierdo lona jak pancie cie dłać na mac do pence kurwa diąć na pc kurwa mać

0 votes     reply to comment
ab2531 Oct 17 2011, 5:27pm says:

It is hard!

+2 votes     reply to comment
Chell_Johnson Jun 7 2012, 10:02am replied:

Sure.Hard,but interesting.

+1 vote     reply to comment
Chell_Johnson Jun 7 2012, 10:01am says:

Something magic is in this mod..and it is not G-Man in the very end,of course!))

+1 vote     reply to comment
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nathan992009 Oct 20 2013, 3:53pm says:

erm it does not work i just have a white screen and then an error saying that it cant find background 1 widescreen.... can anyone help???

+1 vote     reply to comment
Guest May 7 2014, 5:21pm replied:

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Indurok Online
Indurok Nov 22 2014, 3:05am says:

What folder do I put it in to make it work?

+1 vote     reply to comment
Indurok Online
Indurok Nov 22 2014, 3:19am says:

You know what? This game sucks, because I can't figure out how to get it to work.

0 votes     reply to comment
Indurok Online
Indurok Nov 22 2014, 3:31am says:

Never mind, I looked somewhere else, and found something to help, but I just get a white screen.

+1 vote     reply to comment
Indurok Online
Indurok Nov 22 2014, 4:14am says:

Well, I got it to work.

+1 vote     reply to comment
superpie100 Jan 9 2015, 11:37pm replied:

What did you do?

+1 vote     reply to comment
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Released Oct 2008
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