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+# Checking out and Building Thorium for Windows
+
+## System requirements
+
+* A 64-bit machine with at least 8GB of RAM. More than 16GB is highly
+  recommended.
+* At least 75GB of free disk space on an NTFS-formatted hard drive. FAT32
+  will not work, as some of the Git packfiles are larger than 4GB.
+* An appropriate version of Visual Studio, as described below.
+* Windows 10 1709 or newer.
+
+## Setting up Windows
+
+### Visual Studio
+
+Chromium requires [Visual Studio 2019](https://visualstudio.microsoft.com/vs/older-downloads/) (>=16.0.0)
+to build, but [Visual Studio 2022](https://visualstudio.microsoft.com/vs/) (>=17.0.0)
+is preferred. Visual Studio can also be used to debug Chromium, and version 2022 is
+preferred for this as it handles Chromium's large debug information much better.
+The clang-cl compiler is used but Visual Studio's header files, libraries, and
+some tools are required. Visual Studio Community Edition should work if its
+license is appropriate for you. You must install the "Desktop development with
+C++" component and the "MFC/ATL support" sub-components. This can be done from
+the command line by passing these arguments to the Visual Studio installer (see
+below for ARM64 instructions):
+```shell
+$ VisualStudioSetup.exe --add Microsoft.VisualStudio.Workload.NativeDesktop --add Microsoft.VisualStudio.Component.VC.ATLMFC --includeRecommended
+```
+
+If you want to build for Windows on ARM64 then some extra arguments are needed. The
+full set for that case is:
+```shell
+$ VisualStudioSetup.exe --add Microsoft.VisualStudio.Workload.NativeDesktop --add Microsoft.VisualStudio.Component.VC.ATLMFC --add Microsoft.VisualStudio.Component.VC.Tools.ARM64 --add Microsoft.VisualStudio.Component.VC.MFC.ARM64 --includeRecommended
+```
+
+-You must have the version 10.1.20348.0 [Windows 10 SDK](https://developer.microsoft.com/en-us/windows/downloads/sdk-archive/)
+installed. This can be installed separately or by checking the appropriate box
+in the Visual Studio Installer (Note that MSVS 2022 will try to install the 19043 version by default, uncheck this and check the 20348 version).
+There is also experimental support for the Windows 11 10.1.22000.0 version.
+
+The SDK Debugging Tools must also be installed. If the Windows 10 SDK was
+installed via the Visual Studio installer, then they can be installed by going
+to: Control Panel → Programs → Programs and Features → Select the "Windows
+Software Development Kit" → Change → Change → Check "Debugging Tools For
+Windows" → Change. Or, you can download the standalone SDK installer and use it
+to install the Debugging Tools.
+
+## Install `depot_tools`
+
+Download the [depot_tools bundle](https://storage.googleapis.com/chrome-infra/depot_tools.zip)
+and extract it somewhere (eg: C:\src\depot_tools).
+
+*** note
+**Warning:** **DO NOT** use drag-n-drop or copy-n-paste extract from Explorer,
+this will not extract the hidden “.git” folder which is necessary for
+depot_tools to autoupdate itself. You can use “Extract all…” from the
+context menu though.
+***
+
+Add depot_tools to the start of your PATH (must be ahead of any installs of
+Python. Note that environment variable names are case insensitive).
+
+Assuming you unzipped the bundle to *C:\src\depot_tools*, open:
+
+Control Panel → System and Security → System → Advanced system settings
+
+If you have Administrator access, Modify the PATH system variable and
+put `C:\src\depot_tools` at the front (or at least in front of any directory
+that might already have a copy of Python or Git).
+
+If you don't have Administrator access, you can add a user-level PATH
+environment variable by opening:
+
+Control Panel → System and Security → System → Search for "Edit environment variables for your account"
+
+Add `C:\src\depot_tools` at the front. Note: If your system PATH has a Python in it, you will be out of luck.
+
+Also, add a `DEPOT_TOOLS_WIN_TOOLCHAIN` environment variable in the same way, and set
+it to __0__. This tells depot_tools to use your locally installed version of Visual
+Studio (by default, depot_tools will try to use a google-internal version).
+
+You should also set the variable `vs2019_install` or
+`vs2022_install` to your installation path of Visual Studio 19 or 22, like
+`vs2019_install` = __C:\Program Files (x86)\Microsoft Visual Studio\2019\Community__
+for Visual Studio 2019, or
+`vs2022_install` = __C:\Program Files\Microsoft Visual Studio\2022\Community__
+for Visual Studio 2022.
+
+Once all of this is done, we will download some infra archives using `gclient`
+From a cmd.exe shell, run:
+
+```shell
+$ gclient
+```
+
+On first run, gclient will install all the Windows-specific bits needed to work
+with the code, including msysgit and Python.
+
+* If you run gclient from a non-cmd shell (e.g., cygwin, PowerShell),
+  it may appear to run properly, but msysgit, python, and other tools
+  may not get installed correctly.
+* If you see strange errors with the file system on the first run of gclient,
+  you may want to [disable Windows Indexing](https://tortoisesvn.net/faq.html#cantmove2).
+
+## Check Python install
+
+After running gclient open a command prompt and type `where python` and
+confirm that the depot_tools `python.bat` comes ahead of any copies of
+python.exe. Failing to ensure this can lead to overbuilding when
+using gn - see [crbug.com/611087](https://crbug.com/611087).
+
+[App Execution Aliases](https://docs.microsoft.com/en-us/windows/apps/desktop/modernize/desktop-to-uwp-extensions#alias) in Windows 10/11
+can conflict with other installations of python on the system so disable
+these for 'python.exe' and 'python3.exe' by opening 'App execution aliases'
+section of Control Panel and unticking the boxes next to both of these
+that point to 'App Installer'.
+
+## Download the Chromium code
+
+First, configure Git:
+
+```shell
+$ git config --global user.name "My Name"
+$ git config --global user.email "my-name@chromium.org"
+$ git config --global core.autocrlf false
+$ git config --global core.filemode false
+$ git config --global branch.autosetuprebase always
+```
+
+Create a `chromium` directory in *C:\src* for the checkout and change to it.
+
+```shell
+$ cd / && cd src && mkdir chromium && cd chromium
+```
+
+Run the `fetch` tool from `depot_tools` to check out the code and its
+dependencies.
+
+```shell
+$ fetch chromium
+```
+
+If you don't want the full repo history, you can save a lot of time by
+adding the `--no-history` flag to `fetch`.
+
+Expect the command to take 30 minutes on even a fast connection, and many
+hours on slower ones.
+
+When `fetch` completes, it will have created a hidden `.gclient` file and a
+directory called `src` in the working directory. The remaining instructions
+assume you have switched to this directory (i.e. *C:\src\chromium\src*):
+
+```shell
+$ cd src
+```
+
+*Optional*: You can also build with [API
+keys](https://www.chromium.org/developers/how-tos/api-keys) if you want features like Google Sync, Translate, Gelocation API, etc.
+Thorium release builds use a private API Keys repo, if you would like access, contact me. Otherwise you can follow the above link to learn how to make your own private developer keys.
+
+##  Downloading the Thorium code
+
+You can either use git clone, or download a .zip from the repo. It should be placed side by side with the Chromium directory in *C:\src*
+Using Git:
+
+```shell
+$ git clone https://github.com/Alex313031/Thorium.git
+```
+Or download the .zip (Make sure to rename the extracted dir to just Thorium, not Thorium-main).
+[https://github.com/Alex313031/Thorium/archive/refs/heads/main.zip](https://github.com/Alex313031/Thorium/archive/refs/heads/main.zip)
+
+## Setting up the build
+
+First, we need to copy the Thorium source files over the Chromium tree.
+Run the `setup.bat` script in *Thorium\win_scripts* to automate this.
+
+```shell
+$ cd C:\src\Thorium\win_scripts && setup.bat
+```
+It will drop you back to *C:\src\chromium\src*, which is where the rest of the commands will be carried out.
+
+Next, we will download the PGO profile for Thorium, which changes with every revision. Run:
+
+```shell
+$ python3 tools\update_pgo_profiles.py --target=win64 update --gs-url-base=chromium-optimization-profiles/pgo_profiles
+```
+This will download a *.profdata file, looking something like `chrome-win64-main-1659409120-058034bd778fed227d12a29fd0edd0942810dbf8.profdata`
+Take note of this, as we will be using it in the `args.gn` below.
+
+### Creating the build directory
+Chromium & Thorium use [Ninja](https://ninja-build.org) as its main build tool along with
+a tool called [GN](https://gn.googlesource.com/gn/+/main/docs/quick_start.md) to generate `.ninja` files. Create the build directory by running:
+
+```shell
+$ gn args out\thorium
+```
+
+This will open up notepad.exe, and this is where we will specify build arguments ("args") which direct Ninja on how to lay out the build directory tree.
+We will be copy/pasting the contents of the [win_args.gn](https://github.com/Alex313031/Thorium/blob/main/infra/win_args.gn) file from *C:\src\Thorium\infra\win_args.gn* into notepad.
+Notice the three lines at the top, related to API Keys. It is fine to leave them blank, or add the ones you have made.
+__At the bottom__, though, notice the line that says *pgo_data_path = ""*. This is where we will put the full path to the PGO profile data file we downloaded earlier.
+
+That line should look something like:
+
+`pgo_data_path = "C:\src\chromium\src\chrome\build\pgo_profiles\chrome-win64-main-1659409120-058034bd778fed227d12a29fd0edd0942810dbf8.profdata"`
+
+* For other build arguments, and what the ones that Thorium uses do, see [ABOUT_GN_ARGS.md](https://github.com/Alex313031/Thorium/blob/main/infra/DEBUG/ABOUT_GN_ARGS.md) & [win_args.list](https://github.com/Alex313031/Thorium/blob/main/infra/win_args.list)
+* For more info on GN, run `gn help` on the command line or read the [quick
+  start guide](https://gn.googlesource.com/gn/+/main/docs/quick_start.md).
+
+## Build Thorium
+
+Build Thorium, and the other things like chromedriver and thorium_shell with Ninja using the command:
+
+```shell
+$ autoninja -C out\thorium chrome chromedriver thorium_shell setup mini_installer -j8
+```
+(Where -j# can be any number, and should generally be set to the number of cores on your CPU)
+
+`autoninja` is a wrapper that automatically provides optimal values for the
+arguments passed to `ninja`.
+
+You can get a list of all of the other build targets from GN by running
+`gn ls out/Default` from the command line. To compile one, pass to Ninja
+the GN label with no preceding "//" (so for `//chrome/test:unit_tests`
+use autoninja -C out/Default chrome/test:unit_tests).
+
+## Install/Run Thorium
+
+Once it is built, you can simply install the browser.
+
+```shell
+$ out\thorium\mini_installer.exe
+```
+
+## Update your checkout
+
+To update an existing Chromium checkout, you should run the `trunk.bat` script in win_scripts:
+
+```shell
+$ cd C:\src\Thorium\win_scripts && trunk.bat
+```
+(This script will also download the latest PGO profile data file at the end.)
+
+This syncs the subrepositories to the appropriate versions,
+deleting those that are no longer needed, and re-runs the hooks as needed.
+
+To update an existing Thorium checkout, just download the latest .zip, or do a git pull:
+
+```shell
+$ cd C:\src\Thorium\win_scripts && trunk.bat
+```
+
+*Happy Thorium Building!*