Also available: Command line (console) tools htmlval for Linux and htmlval for Mac!

"I have been using the offline Validator S.A.C. but it quit working when Apple released El Capitan. The other Apple friendly validators either don't work or are pathetic. I dusted off my Dell and upgraded my old version of HTML Validator ... Wow! Your validator found critical errors that the S.A.C. program completely ignored."
- Michael Stewart

"I bought Parallels and Windows just to be able to run HTML Validator Pro on my Mac - and it was totally worth it."
- Glen Pipkins, AllWebCo

"WINE has clearly made great progress since I first tried it some years ago, and now allows easy installation and fully functional execution of HTML Validator and several other w32 tools I use with some regularity. But it's the fact that I can use HTML Validator on an Ubuntu box that floats my boat. I can't think of another digital tool that provides me with such effective notice of my errors coupled with sophisticated learning aids."
- Walt Wheeler

"Moving from the PC to a Mac was wonderful. The ONLY software I couldn't find on the Mac was HTML Validator, therefore I bought Virtual PC for the Mac just so I could run HTML Validator. It is the best HTML/XHTML editor and validation tool on the market, and the only one I recommend to fellow Web professionals and my students."
- Dr. Tim Gottleber, author of Even More Excellent HTML and BulletProof Unix

"I bought HTML Validator Pro almost 6 months ago, and have since switched to a near-full-time Linux user. However, I've managed to find an equivalent or better product for every Windows-only product on Linux...except HTML Validator. HTML Validator remains the only stumbling block that keeps me going back to Windows."
- Brian Deragon

How to Run CSS HTML Validator for Windows on a Chromebook, Mac, or Linux

If you don't have Windows then you can still run CSS HTML Validator using a method described below (i.e. Parallels Desktop, Wine, CrossOver, Boot Camp, VirtualBox, etc).

*NOTE: There is now a native Linux command line port (no GUI) and native Mac command line port of CSS HTML Validator (no GUI).

Parallels Desktop for Apple Mac

Use Parallels Desktop to run a virtual Windows operating system on your Mac. This will let you run a variety of Windows applications in the virtualized Windows environment.

Parallels Desktop 18+ works with Windows 11 and improves performance on Apple silicon devices (i.e. M1/M2/Mx devices).

Using Wine (Compatibility Layer for Windows)

Wine 9.0+ is the recommended way to run CSS HTML Validator (with GUI) on a Chromebook, Mac, or Linux if you don't have a virtualized Windows machine and do not want to buy a Microsoft Windows license.

What is Wine?

Wine is a compatibility layer capable of running many (but not all) Windows applications on several POSIX-compliant operating systems, such as Linux, Mac OS X, & BSD. Wine also doesn't require the purchase of Microsoft Windows unlike Parallels Desktop, Boot Camp, VirtualBox, and other OS virtualization products. You'll also save gigabytes of disk space by not needing a virtualized Windows environment.

What will not or may not work with Wine?

The integrated web browser will not work, although using an external web browser should work fine (and this is the recommended testing method anyway).
The Browser View tabs in the Pretty Print/Fix Dialog use the same component as the integrated web browser and will not work either.
Offline help may not work but online help can be used instead (Help > Online Help). Newer versions will automatically redirect requests for help to the online version of help when running under Wine.
Some systems may have a problem with JavaScript checking which requires running node.exe. In at least one test, Wine 4.0 (on a Mac) was not able to run node.exe. However, it worked on a Linux machine.
Because Wine does not come with the sound and media files that Windows comes with, no sound will play after a validation (unless you provide and specify your own sound files in the Validator Engine Options).

Note: If you encounter a clipboard registration issue (that may cause the system to become unresponsive and require a system reboot) then you may be able to resolve it using an alternate method of registration. If you encounter this issue then please contact us.

Wine (Chromebook / ChromeOS)

If you're using a Chromebook, visit How to install and use Wine 9.0 on a Chromebook.

Wine (Mac and Linux)

Download Wine here (new window). If given the option during the installation to support 64-bit programs then choose it in order to support recent versions of CSS HTML Validator.

For Linux visit How to Install Wine on Linux.

For Mac / Mac OS X visit Installing Wine on Mac OS X (new window).

CrossOver (Chromebook, Mac, & Linux)

CrossOver is a polished version of Wine provided by CodeWeavers. CrossOver makes it easier to use Wine.

Boot Camp for OS X

Use Boot Camp to boot into multiple operating systems including Windows.

Boot Camp is available in Mac OS X v10.5 Leopard or higher. See also this Wikipedia article.

VirtualBox (Mac, Linux, Solaris)

You can use VirtualBox (FREE) to run Windows in a virtual environment on a Linux, Mac, or Solaris host. This will not only let you run CSS HTML Validator but also other Windows programs.

Note that while VirtualBox is free, you'll still need a license for Windows (which is not free).

VMware Fusion for Intel based Mac

Legacy Intel-based Macs can also use VMware Fusion to run Windows.