Speed Up Webpack Watch in Windows

May 1, 2019

Photo by Charlotte Coneybeer on Unsplash (https://unsplash.com) Photo by Charlotte Coneybeer on Unsplash

One annoyance of working in Windows in an open-source tech stack is that a lot of the dev tooling isn't as good as on a Mac. The problem rears its ugly head whenever I have to use composer or npm/yarn. Which is pretty much a gazillion times a day. Despite my job laptop having more horsepower than my personal MacBook Pro, the former takes a lot longer to perform any composer or npm task in the terminal.

Don't get me wrong, I'm not a Mac snob. I've used Windows PCs for most of my career, only switching to Mac a few years ago for development and, oh boy, I would never go back to a PC for any kind of PHP/JS or any kind of open-source work in general. Sometimes, though, an employer can insist on a specific platform, hence the subject of this article.

As a quick recap, the Windows 10 Pro environment in question runs from an SSD on an 8th-gen i7 machine with 16GB RAM. I typically use GitBash as my terminal of choice. I've tried the built-in Ubuntu shell as well as ConEmu which does a somewhat reasonable job of allowing multiple tabs, though it's buggy and I gave up on it. Instead, I just open multiple GitBash windows which is less than ideal but is mitigated by the fact that I have 3 screens at my disposal.

The main project I'm building and maintaining is a Laravel app with lots of Vue sprinkled in, in the form of single-file components.

Whenever I work in Vue, I fire up yarn watch <-- Yarn master race 🙂. Well, here's what used to happen every time I saved my work. Webpack went through it's build process, but got stuck for a very long time at 91% with this message:

WAIT Compiling... 10:49:04 AM

91% additional asset processing

The whole process took close to 30 seconds. You can imagine this adds up throughout the day. It's long enough to be frustrating but short enough that I can't do anything else in the meantime but twiddle my thumbs.

Having chalked it down to Windows being... Windows, I just about gave up on a good dev experience, until I decided to seek a possible solution.

Well, despair no more fellow Windows hostages. This quick setting will speed up Webpack while it's watching for changes. Just add devtool: 'eval' to your Webpack config as shown:

    devtool: 'eval',
    plugins: [],

Keep in mind that the Webpack configuration above is taken from a Laravel 5.8 project, meaning it's wrapped inside Laravel Mix but in a regular Webpack project you can use the same method.

You'll need to restart yarn watch after adding this setting, but the watch build time drops down to 1.5-10 seconds, a 2x - 15x speed increase 🚀!

Digging deeper

What I failed to mention (and it's an important one!) is that I don't use this technique in production, but merely in my local dev environment. In fact Webpack mentions just that in the devtool documentation.

If you are curious if there's any different in the production bundle size without this option and after applying it, yes there is. Using devtool: 'eval' produces a larger bundle. Here's a comparison (the CSS bundles are omitted because their size is not affected). The biggest difference is in the vendor bundle

With devtool: 'eval':

DONE Compiled successfully in 32631ms 10:12:56 AM

      Asset           Size       Chunks               Chunk Names
/js/app.js           656 kB        1         [emitted] [big] /js/app 
/js/vendor.js       1.25 MB        3         [emitted] [big] /js/vendor

Done in 37.33s.

Without devtool: 'eval':

DONE Compiled successfully in 78692ms 10:23:16 AM

      Asset          Size        Chunks                Chunk Names
/js/app.js          407 kB         1          [emitted] [big] /js/app 
/js/vendor.js       345 kB         3          [emitted] [big] /js/vendor

Done in 83.60s. 

Happy Webpacking!

Laravel Vue Webpack Windows10
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