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Open source mod for Halo: Combat Evolved on the PC
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Chimera is a mod for Halo: Combat Evolved for the PC. It is licensed under version 3.0 of the GNU General Public License. See LICENSE for more information.

Table of contents


Here is the installation procedure for installing Chimera:

  1. Update your installation of Halo to version 1.10.
  2. Back up your game's Strings.dll. Renaming it to strings-old.dll works.
  3. Copy strings.dll and chimera.ini into your game folder.

NOTE: Each file goes into the main game folder, NOT controls. If you put the files in controls, it will not work.

Uninstalling Chimera is simple:

  1. Delete Chimera's strings.dll and (optionally) chimera.ini.
  2. Rename your backed up copy of Halo's Strings.dll back to strings.dll.

Mod support

Chimera does not support any binary mods like HAC2 or Open Sauce. The reason for this is because they modify the game in similar ways, resulting in them conflicting with one another. Supporting just one of these mods would mean extra development time that I don't have. Sorry.

That said, you can create a mods folder and drop in binary mods in there.


Chimera provides a number of features and enhancements to the base Halo game. To ensure the base game is preserved as much as possible, most features are not turned on by default, and the ones that are only exist to enhance or fix the game.

Passive features

These are features that are always on.


The game has an issue where object movement is tied to tick rate, thus objects will never move faster than 30 frames per second. Chimera adds interpolation to the game for objects. Unlike MCC, it also adds it for particles, too.

Limit increase

Chimera increases some of the limits of the game. Note that, unless you play a map that exceeds these limits, your performance will not be impacted. If you don't have this on, then maps that exceed the limits will look incorrect and may not even be playable. Therefore, this feature is always on. Here are the increases:

  • BSP polygon limit boosted to 32767
  • Visible object limit boosted to 1024
  • Draw distance increased to 2250 world units (~6.86 km)

Compressed maps

Chimera supports Invader-compressed maps. This allows you to take advantage of the blazingly fast zstd compression algorithm, drastically cutting down map size.

If maps in RAM is enabled, compressed maps will be decompressed directly into RAM. Otherwise, temp files will be used.

Reduced DRM

Normally, Halo does not allow you to join servers with someone that has the same CD key. This was done to prevent people from sharing CD keys. However, this protection has shown to not work and, as a result, is purely an hindrance to people who have legitimate copies of the game, such as modders. By disabling the CD key check, you can locally host a game that lets you join yourself.

Note that this feature does not "crack" the game. You still need a valid Halo installation in order to run the installer for the game as well as update the game to 1.10.

Descope fix

When you take damage while zoomed in, the game zooms back out automatically. This functionality is broken when in a server, as the client only descopes when the player takes damage on the client instance rather than if they actually took damage on the server. Chimera changes this to making it so if you lose health or shield, you are descoped.

Fast loading

Halo Custom Edition CRC32s every map on startup. On a small maps folder, this does not significantly increase loading time. On a massive maps folder, this drastically increases loading time, ranging from seconds to minutes.

Some mods "fix" this by storing the CRC32 in a cache, but this negates the point of it in the first place, as now you can join servers with mismatched CRC32s. Chimera truly fixes it by CRC32ing the map when you load the map, not the game.

Fast server listing

The game takes forever to query the master server. Chimera speeds it up.

128 MiB map leak fix

If you load a map that exceeds 128 MiB, the game opens the map multiple times and only closes it once. This results in the map leaking, and eventually, the game could run out of file descriptors. Chimera fixes this by removing the file size check.

Model LOD fix

The game uses your vertical resolution to determine how detailed to draw a model. However, this results in levels like The Pillar of Autumn showing the highest LOD for some mods when it shouldn't, leading to infamous glitches like the "4K headless chief" glitch. Chimera makes it scale by 480p, instead.

FOV fix

There is a bug in the game where, when you increase the vertical resolution of the game, your FOV gets slightly more narrow, even if you are on the same aspect ratio. Chimera fixes this so FOVs stay consistent between vertical resolutions. This does NOT fix low FOV at widescreen aspect ratios, which is what chimera_fov is for.

Sun fix

Lens flares are drawn at a set number of pixels regardless of vertical resolution. Chimera makes it scale by 768p, instead.

Custom chat

The Keystone chat is crashy and broken. Chimera adds a replacement chat.

NVIDIA camo fix

Chimera fixes a bug where, if the GPU is an NVIDIA graphics card, it uses alpha blended camo instead of the liquid camo shader.

Map downloading

Chimera will automatically attempt to download maps off of the HAC2 Map repo upon joining a server that is playing a map you don't have. These maps are stored under chimera/maps in your Halo profiles folder.

Ini features

Chimera has a very customizable chimera.ini text file that you can use to further tweak your game.

Note that .ini comments start with a ; and some features are commented out (disabled) like so: ;enabled=1. This is so if you want to enable a feature, you simply have to remove the semicolon.

Below are the features you can take advantage of.

Halo settings

These features exist to prevent the need to use arguments for the Halo executable.

  • path (changes the profile path location)
  • main_menu_music (disables the music in the main menu)
  • server_port (set the default server port)
  • client_port (set the default client port)

Memory settings

This feature exists to allow you to take advantage larger amounts of RAM, reducing hiccups and stutters, especially on slower storage. However, you will need an LAA-patched executable to use this feature.

  • enable_map_memory_buffer (enables loading maps directly into RAM)
  • benchmark (shows a benchmark whenever a map is loaded)

Video mode

These settings allow you to change Halo's video settings without requiring vidmode. You can even use refresh rates in excess of 120 Hz.

  • enabled (enables the feature)
  • width (default width in pixels)
  • height (default height in pixels)
  • refresh_rate (refresh rate in Hertz)
  • vsync (enable double buffer vSync to reduce tearing)
  • windowed (display Halo in a window)

Custom chat settings

This allows you to customize the different colors, positioning, and timings of Chimera's chat. When we said it was a custom chat, we meant it. See the included chimera.ini file for more information on these settings.


This allows you to execute Chimera commands, Halo commands, or Halo scripts when the key combination is invoked. See the included chimera.ini file for more information on these settings.


Chimera provides a number of extra features that can be turned on. Most of these features are off by default. Commands are stored in preferences.txt in the chimera folder created by Chimera.

Aim assist

Halo's aim assist was broken in the PC release. Chimera fixes it. By default, this feature is on. It only works for analog sticks, though.

Usage: chimera_aim_assist [true/false]

Anisotropic filtering

This enables the same thing that is done in config.txt but without having to edit it. Note that this only applies to the level geometry, not individual objects. You'd need AF enabled externally to do that.

Usage: chimera_af [true/false]

Auto centering

In stock Halo, vehicle auto centering is based on frame rate. Chimera allows you to either fix it or turn it off completely, as this can be annoying.

  • 0 is Halo's normal behavior
  • 1 is fixed behavior (tick-based)
  • 2 is no auto centering whatsoever

Usage: chimera_auto_center [0/1/2]

Auto uncrouching

When on the ground, the game disabled crouching if the player was running at full speed. You can re-enable this behavior if you want.

Usage: chimera_auto_uncrouch [true/false]

Block all bullshit

This feature runs the following commands:

  • chimera_block_buffering 1
  • chimera_block_camera_shake 1
  • chimera_block_gametype_indicator 1
  • chimera_block_gametype_rules 1
  • chimera_block_hold_f1 1
  • chimera_block_loading_screen 1
  • chimera_block_zoom_blur 1
  • chimera_block_mouse_acceleration 1

Usage: chimera_block_all_bullshit

Block buffering

This feature is known to reduce input lag, and it works like the feature in config.txt. You can enable this behavior if you want.

Usage: chimera_block_buffering [true/false]

Block camera shaking

Camera shaking from taking damage or firing weapons is broken in Halo PC. You can disable it if you want.

Usage: chimera_block_camera_shake [true/false]

Block gametype indicator

The original Xbox version of the game didn't have the gametype indicator, and it looks out of place in most custom maps. You can disable it, if you want.

Usage: chimera_block_gametype_indicator [true/false]

Block gametype rules

In Halo Custom Edition, if you join a server, you see the gametype rules for a few seconds (or part of a second depending on frame rate). If this is annoying, you can disable it.

Usage: chimera_block_gametype_rules [true/false]

Block hold F1

When you join a server, you'll see a "Hold F1 for score" (or whatever button is bound to score screens). You can disable this if you want.

Usage: chimera_block_hold_f1 [true/false]

Block letterbox

Cutscenes have a letterbox. You can disable it if you want.

Usage: chimera_block_letterbox [true/false]

Block loading screen

When you join a server, you are blinded for a few seconds by a loading screen, and this can make you susceptible to being cheaply killed. This disables that loading screen. By default, Chimera disables the loading screen due to this, but you can turn it back on if you want.

Usage: chimera_block_loading_screen [true/false]

Block mouse acceleration

Halo uses raw input, thus it bypasses the mouse acceleration setting of your operating system (unless you run the game in Wine). However, Halo adds its own mouse acceleration on top of direct input. You can disable this if you want. By default, mouse acceleration is blocked.

Usage: chimera_block_mouse_acceleration [true/false]

Block server IP

This hides the server IP from view in the score screen. This is good for streamers who don't want people to join what server they are in. You can enable this feature if you want.

Usage: chimera_block_server_ip [true/false]

Block zoom blur

Halo's zoom blur looks like ass on high resolutions. This feature removes it without requiring you to use DisableAlphaRenderTargets or safe mode.

Usage: chimera_block_zoom_blur [true/false]

Bookmark add

Add a server to the server bookmarks list. If no server details are given, then the last server joined is added. You can use a domain name in place of an IP.

Usage: chimera_bookmark_add [ip:port [password]]

Bookmark delete

Delete a server from the server bookmarks list. Either an index or an ip:port can be used. If no server details are given, then the last server joined is deleted.

Usage: chimera_bookmark_delete [ip:port | index]

Bookmark connect

Connect to a server in the bookmarks list.

Usage: chimera_bookmark_connect <index>

Bookmark list

List and query all bookmarked servers.

Usage: chimera_bookmark_list

History connect

Connect to a server in the recent server list.

Usage: chimera_history_connect <index>

History list

List and query all recent servers.

Usage: chimera_history_list


Show the different budgets in Halo, including object limit and BSP polygon limit.

Usage: chimera_budget [true/false]

Chat: Block IPs

Block IPs from being shown in the custom chat. This is good for streamers, so their IPs don't get shown on stream. It requires custom chat to be enabled.

Usage: chimera_chat_block_ips [true/false]

Chat: Block server messages

Block all messages from the server except for if you're using rcon in the console.

Usage: chimera_chat_block_server_messages [true/false]

Chat: Chat color help

Show fancy chat colors you can use.

Usage: chimera_chat_color_help [true/false]

Console prompt color

Set the console input color.

Usage: chimera_console_prompt_color [<red> <green> <blue>]


Set deadzones for analog input.

Usage: chimera_deadzones [deadzones]


Enable devmode commands without blocking you from multiplayer or requiring any command line arguments.

Usage: chimera_devmode [true/false]


Set the diagonals for moving with an analog stick. By default, this is set to 0.75, as Halo's default diagonals make it difficult to move with an analog stick. This is because Halo converts it to digital input, as the netcode does not support analog movement.

Usage: chimera_diagonals [true/false]

Enable console

Enable the console without command line arguments. This is on by default.

Usage: chimera_enable_console [true/false]


Set FOV. End with "v" to lock to a vertical FOV, or use "auto" to set to an automatic FOV. Using a vertical FOV over a horizontal one helps prevent the game from distorting your field of view when switching aspect ratios. On Halo Trial, this feature will be set to "auto" by default.

Usage: chimera_fov [fov]

HUD kill feed

Put the kill feed in the HUD. Halo puts it in the chat, normally. This feature is on by default.

Usage: chimera_hud_kill_feed [true/false]


Chimera is localized for both English and, thanks to help from the community, Spanish. By default, it is English.

Usage: chimera_language [en/es]

Model detail

Change the model detail. Higher values increase LODs. This will not make models extra detailed. Instead, it will change the threshold for when higher LODs appear. Extremely high values will cause the aforementioned "4K headless chief" glitch, except at any vertical resolution this time. By default, this is set to 1.0.

Usage: chimera_model_detail [detail]

Mouse sensitivity

Set the mouse sensitivity. This is more granular than using Halo's settings. It is recommended to have mouse acceleration disabled if using low values.

Halo Horizontal Vertical
10 4 2
9 4 2
8 3 1.5
7 2 1
6 1.5 0.75
5 1.25 0.625
4 1 0.5
3 0.75 0.375
2 0.5 0.25
1 0.25 0.125

Usage: chimera_mouse_sensitivity [off | <horizontal> <vertical>]

Player info

Show player info for the given player.

Usage: chimera_player_info <player>

Player list

List player indices.

Usage: chimera_player_list

Set name

Set your in-game name.

Usage: chimera_set_name [name]

Show coordinates

Show your in-game coordinates.

Usage: chimera_show_coordinates [true/false]

Show FPS

Show your in-game FPS.

Usage: chimera_show_fps [true/false]

Shrink empty weapons

Make empty weapons appear smaller so they're easier to spot.

Usage: chimera_shrink_empty_weapons [true/false]

Split screen HUD

Override the HUD with the split screen HUD.

Usage: chimera_split_screen_hud [true/false]


Spectate a specific player. Use 0 to disable spectating.

Usage: chimera_spectate <index>

Spectate next

Spectate the next player. This is intended to be used with hotkeys.

Usage: chimera_spectate_next

Spectate previous

Spectate the previous player. This is intended to be used with hotkeys.

Usage: chimera_spectate_back

Spectate team only

Set whether or not chimera_spectate_next or chimera_spectate_previous selects players not on the same team. This has no effect on non-team games.

Usage: chimera_spectate_team_only <enabled>

Throttle FPS

Throttle Halo's frame rate. Set to 0 to disable. By default, this is set to 300 on Halo Trial.

Usage: chimera_throttle_fps [FPS]


Set the game's tick rate. This will not work outside of client hosted games. For reference, the game runs at 30 TPS by default.

Usage: chimera_tps [TPS]

Uncap cinematic

Uncap the cinematic frame rate from 30 FPS. This will be turned on by default on Halo Trial.

Usage: chimera_uncap_cinematic [true/false]

Widescreen fix

Fix the scaling of HUD, menu, and text elements for wider aspect ratios. This may break some maps, and this will not be fixed as fixing one thing will break another thing due to the nature of these fixes. On Halo Trial, this will be on by default.

Usage: chimera_widescreen_fix [true/false]


Will Chimera run on my system?

Chimera isn't too taxing, especially on modern systems, but it can make Halo harder to run if you're on very ancient hardware.

There are the hard requirements:

  • OS (if on Windows): Windows 7 or newer
  • Wine (if on Linux): Wine 4.0 or newer*

*We test on the latest wine-staging 5.0 version, but 4.0 should work.

If your PC does not at least meet the above requirements, Chimera may fail to run properly due to the underlying API being older.

There are the recommendations for running Chimera optimally:

  • CPU (Intel): Intel Core i3-2100 (3.1 GHz) or better
  • CPU (AMD): AMD FX 6100 (3.3 GHz) or better
  • RAM: 8 GiB or more*
  • GPU (Nvidia): Nvidia GeForce 8500 GT
  • GPU (AMD): ATI Radeon HD 5670 or better
  • GPU (Intel): see Nvidia and AMD requirements

* Halo, even with Chimera, is 32-bit, so it won't technically use more than 4 GiB, but 8 GiB is recommended so Chimera has enough RAM.

The newest of the above requirements is the AMD CPU (FX 6100) which was released in the year 2011 - over seven years ago at the time of writing this sentence.

Can I use Chimera under a license besides GNU GPL version 3?

Short answer: Probably not.

Long answer: It's not impossible. You would first need to ask all of the developers of upstream Chimera for permission. Chimera, however, also depends on Invader for map compression, and this is licensed under the GPL as well. So, you'd have to either remove the Invader dependency (thus no map compression - required for map downloading!) or ask all of the developers of upstream Invader for permission, too.

What is the password to the archive?

Read PASSWORD.txt.

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