Swift 6.4 is ready to install: this repository is ready to modify
Swift 6.4 was the latest release when we checked, and most developers should start there. The language is memory-safe by default, has native access to C and Objective-C, and includes high-level features such as protocols, closures, and generics. A released toolchain gives an application developer the compiler and package tools. This repository is the source underneath them, including the compiler, standard library, tests, documentation, and utilities used by people who change Swift itself. The code uses the Apache 2.0 license with a runtime library exception.
That difference decides whether this is a sensible download. Building an iOS or server application does not require a local compiler build. Changing type checking, code generation, interoperability, or the standard library does. The contributor setup uses utils/update-checkout to bring in related repositories such as LLVM and SwiftPM, then uses utils/build-script over CMake and Ninja. A branch or tag has to match across those checkouts. Our measured tree already held 33,017 files before any sibling projects entered the picture.
Compiler development asks for 150 GB and several repositories
The official guide recommends 150 GB of free disk. It says the source with full Git history takes about 3.5 GB, while build artifacts can occupy 5 GB to 100 GB depending on settings. RAM guidance starts at 8 GB for a toolchain build and rises to 16 GB for development. Virtual machines may need more than 32 GB. Those figures put Swift compiler work firmly on a workstation or a well-sized development server.
Platform setup has its own edges. macOS builders need the required Xcode release, which can change often. Linux builders need a released Swift toolchain because some compiler components are written in Swift. The documented host path covers macOS and Ubuntu Linux. Windows development remains experimental. The guide also warns that spaces or non-ASCII characters in the checkout path can cause failures, and Apple Silicon tools must run natively rather than through Rosetta. Our 3-CPU Debian run did not exercise that compiler path.
What happened when we ran it
Our sandbox checked out commit 0cba8dd, containing 33,017 files, roughly 3,612,121 lines of source, and 213.2 MB on disk. We targeted the Python package in utils/cmpcodesize, not the Swift compiler. Installation succeeded in 33 seconds, added 36 packages, and used 37 MB. The package build succeeded in 4 seconds. Pytest then passed all 3 tests in 4 seconds, and pip-audit reported 0 known vulnerabilities.
The container had 3 CPUs, 8 GB of RAM, Debian, Python 3.12, no secrets, and no elevated privileges. The repository scan found a tests directory, 0 CI workflow files, and no Dockerfile. That last pair describes the files our scanner found, not the absence of project automation. Swift's README points contributors to separate continuous-integration documentation, and its toolchain script is used by Swift.org CI.
Three passing tests cover a code-size helper, not Swift
cmpcodesize compares old and new Swift compiler build products. It accepts explicit files or two build directories, can list function sizes, and can emit CSV. Its default shortcuts refer to benchmark binaries and libswiftCore.dylib. That makes it useful after you already have compiler outputs to compare. The 37 MB installed footprint we measured does not include those outputs, the sibling source trees, or a compiled Swift toolchain. Its packaging metadata calls the utility alpha software, a fair description of this narrow developer aid.
The test file at commit 0cba8dd checks 3 behaviors of the function-size listing helper: a bad input raises an error, an empty input returns an empty list, and entries are ordered by size. The implementation calls Apple's otool to inspect binaries. All 3 tests passing is a clean result for that helper. It is not evidence that the type checker, optimizer, runtime, or standard library passed their own suites.
A 9,426-item queue is moving on the same day
GitHub reported 70,482 stars and 9,426 open issues and pull requests when we fetched the repository data. The latest push was October 7, 2026, and recently updated work included the standard library, C++ interoperability, compiler crashes, and flaky tests. The latest release, Swift 6.4.0, was published on September 15. The queue is enormous, but the push date and current issue activity show a project being worked on daily rather than left behind.
The documentation earns its keep here. It explains the multi-repository checkout, supported hosts, hardware guidance, incremental builds, debugging, testing, and the first-pull-request process. Contributors without write access must ask a reviewer to trigger the CI bot, another detail worth knowing before investing in a change. Swift is easy to obtain as a toolchain. Its source repository is a serious compiler workspace, and the 150 GB recommendation is the clearest line between those two experiences. For most Swift users, the right action is to install the release rather than clone the compiler.