Requirements

macOS

macOS 13 (Ventura) or later to run — macOS 15 (Sequoia) for everything

Two numbers, on purpose. Through 0.8.6 the floor was macOS 15; now the app runs on macOS 13 and 14, and it says so itself: at first launch on such a Mac the wizard reads “This Mac runs macOS 13.6 — rexenv works here with older versions of some components and without PostgreSQL and PHP 8.0. Everything is available on macOS 15 or later.” Below 13 nothing is offered a download.

What “older versions” means is a different pin per component — the last build of each that still loads on that macOS, measured on both chips before it was pinned. The exact numbers are on every row of Pinned versions; in short, on macOS 13:

Component	macOS 15+	macOS 13
MySQL	8.4.6 / 8.0.44	8.4.3 / 8.0.40
MariaDB	12.3.2 / 11.4.12	12.0.2 / 11.4.8
Redis	8.8.0	8.2.1
Apache	2.4.68	2.4.65
Xdebug	3.5.3 for 8.1–8.5	3.4.5 for 8.1–8.4 — none for 8.5
cloudflared	2026.6.1	2025.4.0 (also on macOS 14)
PostgreSQL	18.6 / 17.11 / 16.15	not available (macOS 14: 16.4.0 only)
PHP 8.0	8.0.30	not available

macOS 14 differs from 15 in only two rows: cloudflared 2025.4.0 and PostgreSQL 16.4.0 alone. Everything else on 14 is the standard pin.

What is not available is refused by name, with the macOS it needs, wherever you could choose it — the Databases page, the New Site dialog’s Database field, rex db versions and the agent tools all answer with the same sentence, for example “Needs macOS 14 or later — this Mac runs macOS 13.6.” The row stays visible with that reason; nothing is silently hidden. PHP 8.0 sits in Settings with the sentence as a badge and its Install button off.

Upgrading the Mac later moves you to the current pins

The tier is worked out from the running macOS at every launch and never stored. Upgrade a 13 or 14 Mac to 15 and the next launch of rexenv starts MySQL 8.4.6 on the data that 8.4.3 wrote, MariaDB 12.3.2 on 12.0.2’s, and offers PostgreSQL and PHP 8.0 as ordinary rows — measured on a 13.6 → 15.8 upgrade of the same machine before the release shipped. Nothing moves the other way; macOS does not downgrade.

What a 13 / 14 Mac gives up, honestly

The legacy pins are older builds and stay older: MySQL 8.4.3 is a few security patches behind 8.4.6, and cloudflared 2025.4.0 is more than a year old — if Cloudflare’s edge stops accepting it, sharing a site on 13 / 14 becomes a refusal naming macOS 15. Homebrew publishes no new macOS 13 builds of Redis, MariaDB or Apache any more, so those three cannot move on 13 until rexenv builds its own.

Two floors moved after 0.4.0, both by measurement

Until 0.4.0 the PostgreSQL builds rexenv pinned were compiled for macOS 26, and the site said so. The current pins are measured at macOS 15 on every executable and library in all six tarballs, so PostgreSQL now runs wherever rexenv does. In the other direction, 0.4.0’s nginx build carried a macOS 26 floor on its Intel slice that nobody had measured — an Intel Mac on macOS 15 could install rexenv and then not serve a site. rexenv now builds its own nginx, at macOS 12 on both chips. See the changelog.

Intel or Apple Silicon

One universal build runs natively on both. There is no separate download to choose and no Rosetta involved.

An internet connection on first run

rexenv does not bundle its stack. It downloads each component — PHP, nginx, Caddy, MySQL, Mailpit and the rest — the first time you actually use it, verifies it against a pinned checksum, and prepares it for macOS.

Budget up to ~600MB across a full cold start, spread over your first few actions rather than taken all at once. After that rexenv works offline; nothing re-downloads unless you add a component you have not used before.

The reason it works this way rather than shipping a 600MB app: you get seven PHP versions, four database engines and three web servers available on demand, and you only pay for the ones you touch.

Disk

Plan on 2–4GB for a working setup: the app itself is small, the downloaded components are most of it, and your databases sit alongside them under ~/Library/Application Support/dev.rexenv.rexenv/. Your sites are in ~/rexenv/Sites.

Ports

rexenv binds 80 and 443 for the edge proxy, and a set of high ports for everything else — deliberately offset from the usual defaults so it never collides with a MySQL, Mailpit or nginx you already run.

If something else already holds 80 or 443, rexenv tells you what is holding it rather than failing quietly. rex doctor reports the same from a terminal.

What it does not need

• No Docker, no VM, no Homebrew installation of the stack itself.
• No /etc/hosts editing. A DNS resolver handles *.rex for you.
• No Xcode, and no Command Line Tools, for the stack — Caddy, nginx, PHP, MySQL, Mailpit, Adminer and WP-CLI all install on a Mac that has never seen a compiler, and so do Redis, MariaDB, Apache and Xdebug.

Only git still wants the Command Line Tools

Creating a site from a Git repository, and adding a plugin or theme from one, run git — and on macOS git arrives with the Command Line Tools. Without them rexenv says so, naming xcode-select --install, rather than letting macOS pop its install dialog from a background task. Nothing else in the stack needs them.

This took two fixes. Through 0.7.2, preparing any downloaded binary asked otool, itself a Command Line Tools shim, so on a clean Mac the first cold run failed every component. After that, four still failed: Redis, MariaDB, Apache and Xdebug come as Homebrew bottles whose library paths must be rewritten, and that step was install_name_tool — also the tools. Since 30 September 2026 rexenv rewrites those paths itself. That is proven on a real bottle library against Apple’s own tools; the four installs on a Mac with no tools at all have not been run yet.

Windows

Windows 11 x64

Windows 10 22H2 is best-effort — it left mainstream support on 14 October 2025, and nothing on it is measured.

arm64 is unsupported, and not merely unbuilt. The x64 build runs under emulation on an arm64 machine, but the official PHP Windows builds are x86/x64 only and PostgreSQL’s portable build is x64 only — there is no native stack to ship, so rexenv does not pretend there is one.

An internet connection on first run

rexenv does not bundle its stack. It downloads each component — PHP, Caddy, nginx, MySQL, PostgreSQL, Mailpit, cloudflared — the first time you use it, checksum-verified, then works offline.

The Windows artifacts are the same versions as macOS from different publishers: PHP from php.net’s NTS builds, nginx from nginx.org, MySQL from Oracle’s CDN. Every one is pinned to a digest rexenv downloaded and hashed itself.

Disk

The app installs to %LOCALAPPDATA%\rexenv at about 37 MB. The components and your databases land under %LOCALAPPDATA%\rexenv\rexenv\data, your sites in %USERPROFILE%\rexenv\Sites — plan on 2–4GB for a working setup, the same as macOS.

Ports

The edge proxy binds 80 and 443, and the DNS answerer binds 53 on 127.0.0.1 — Windows’ NRPT has no port field, so it cannot be offset the way macOS’s 15353 is. Everything else is on the same high, offset ports as macOS.

Two things follow from binding loopback only:

• No Windows Defender Firewall alert on first run, because nothing listens on a routable address.
• Your sites are reachable from this computer only. Sharing one publicly is Tunnels, which dials out rather than opening a port.

Binding 80 and 443 needs no administrator approval on Windows — measured under an ordinary unelevated account.

The Microsoft Visual C++ Redistributable (x64)

PHP and MySQL’s Windows builds link it, and a fresh Windows 11 install does not always have it. Without it, no database and no PHP can start — rexenv checks for it before Start all touches either, rather than letting MySQL die with a bare exit code. Settings, rex doctor’s Runtime line, and the installer itself (skipped on a silent /S install) all offer the same link: https://aka.ms/vs/17/release/vc_redist.x64.exe.

What it does not need

• No Docker, no VM, no WSL. This is a native Windows build.
• No hosts file editing. rexenv never touches it: that file is shared by every tool on the machine, and rexenv’s rule is never to overwrite a file somebody else owns. It uses an NRPT rule instead.
• No compiler, and no build tools.

Five components are not in this build

Apache, FrankenPHP, Xdebug, Redis and MariaDB. Each is refused by name with the reason rather than offered and then failing — Install has the table, and Pinned versions marks the rows.

MySQL 8.4 and 8.0 both ship, so a site has a database either way, and PostgreSQL’s three majors are there for Laravel.

WebView2

The installer fetches Microsoft’s WebView2 runtime if your machine does not already have it. Windows 11 ships it, and Windows 10 22H2 usually has it through Windows Update, so on most machines nothing is downloaded.

Linux

Ubuntu 22.04 LTS or newer, x86_64 or arm64

22.04 is the floor for two reasons. It is the first LTS with libwebkit2gtk-4.1, which the app’s window needs, and the release is built on it, so its glibc is the oldest the binary runs against. The one-command installer refuses 20.04 with a sentence saying so.

Newer releases are covered, including where Ubuntu renamed a library MySQL or PostgreSQL loads — libaio1t64 on 24.04 and later, libxml2-16 on 26.04. There rexenv keeps a private symlink under its own data folder that bridges the old name, so both engines start; the .deb declares either spelling. Measured on Ubuntu 22.04 arm64 with a GNOME desktop, and on 22.04 and 26.04 x86_64.

Other distributions with systemd-resolved and polkit will probably work, and none has been tested. The AppImage exists for them; a distribution without apt gets it from the one command.

Both architectures get a native build of every component — every publisher rexenv pins ships an arm64 Linux build, so nothing runs under emulation.

systemd-resolved

.rex is routed through a dummy network link that systemd-resolved sends only .rex names to, so resolved has to be what answers /etc/resolv.conf — Ubuntu’s default. Where it is not running, the setup step refuses with a sentence saying so and writes nothing.

A desktop, with polkit

The app is a desktop window (WebKitGTK) with a tray icon, and every system change goes through pkexec — your desktop’s own password dialog, so a polkit authentication agent must be running, as it is on any Ubuntu desktop. The tray icon needs libayatana-appindicator3; the .deb pulls it in.

An internet connection on first run

rexenv does not bundle its stack. It downloads each component the first time you use it — the same versions as macOS, from each publisher’s own Linux build: Caddy, nginx, PHP from static-php.dev (7.4 is rexenv’s own), MySQL from Oracle’s CDN, PostgreSQL, Mailpit and cloudflared — every one pinned to a digest rexenv hashed itself, then it works offline.

Disk

The .deb is about 15 MB to download and 45 MB installed; the AppImage about 87 MB. The components and your databases land under ~/.local/share/rexenv ($XDG_DATA_HOME/rexenv if you set it), your sites in ~/rexenv/Sites — plan on 2–4GB for a working setup, as on macOS.

Ports

The edge proxy binds 80 and 443, run as root by a systemd unit because only root may bind below 1024. The DNS resolver is on 15353, loopback-only, as on macOS. Everything else is on the same high, offset ports as the other two platforms.

What it does not need

• No Docker, no VM. This is a native Linux build, for x86_64 and arm64.
• No /etc/hosts editing. rexenv never touches it, nor a global resolver configuration — the .rex route is rexenv’s own link, removable without touching anything anybody else wrote.
• No compiler, and no build tools.

Four components are not in this build

Apache, Xdebug, Redis and MariaDB. Each is refused with a message naming Linux rather than offered and then failing — Install says why, and Pinned versions marks the rows. FrankenPHP ships, and so do MySQL 8.4 and 8.0 and PostgreSQL’s three majors.

One user account per machine

On all three systems the web server on :443, the .rex DNS route and the resolver’s port are machine-wide, so a second account on the same machine cannot run its own rexenv beside the first — its services would find those ports taken. Use rexenv from one account. On Windows there is one more machine-wide piece, the \rexenv\dns-agent scheduled task. A second account’s launch finds it registered for the first and leaves it alone — its log says the task is “registered for another account on this computer”, naming that account’s SID — and .rex is answered by that second copy only while it runs. Through 0.8.10 the second launch silently took the task over, so the resolver then started at the wrong account’s sign-in.