Using Dart Sass with Hugo: some data on using GitHub Actions

After encountering some surprising results with my GHA-based method, I decided to do the math.

2022-07-05
Last modified 2022-07-22

Cutting to the chase . . .

If you have a Hugo website hosted by Vercel and you followed my earlier advice about using a GitHub Action (GHA) to deploy that site with Embedded Dart Sass, it turns out you may be better off using either the npm sass package or a shell script — each of which I explain in the links. To learn why, read on; but that’s the bottom line.


In the process of using that GHA to deploy Ye Olde Hugo Site, here, I’ve noticed some curiosities — especially where one particular hosting provider is concerned — so I decided to collect some data, run some tests, and collect more data.

I did so on the only three Jamstack hosting providers I recommend these days, in alphabetical order: Cloudflare Pages, this site’s incumbent host as of the initial publication of this post; Netlify; and Vercel, the site’s backup host.

Now, the details.

From speedster to snail

Soon after I began using the GHA-based method to deploy the site to both its primary target at CFP and its backup target at Vercel, I began noticing that Vercel’s deploy speeds were lagging considerably behind those of CFP’s. As those of you who’ve ever used Vercel with Hugo probably know, such sluggishness is exactly the opposite of what happens whenever you deploy a Hugo site using the normal (non-GHA) Vercel process: usually, Vercel flies. Thus, I went back through the site repo’s GHA logs for the last few weeks, comparing the two hosts’ respective deploy times — and becoming more puzzled with each such examination.

Before I go on: truth be told, I included Netlify in this testing only briefly, at the end, mainly as a sanity check regarding the Vercel-specific data that I’ll describe below. I found Netlify’s performance pretty much as I’d expected from my previous use of that host to build the site with a GHA (about which I wrote two years ago): the total deploy time averaged just over a minute (68.25 seconds, to be exact), of which 35.5 seconds involved the act of actually publishing the Hugo-built site to the Netlify CDN. Given the small size of Netlify’s non-Enterprise-tier CDN, that’s not really impressive, but it still is consistent with previous tests I’ve run. Anyway: the point is, I was using Netlify only as one more point of comparison to see whether there might be something about just using a GHA that might be causing Vercel’s woes (spoiler alert: nope).

In a further effort to nail down what was going on with the GHA-based process and Vercel, I tried both of the two most popular GHAs available for use with Vercel (amondnet/vercel-action and BetaHuhn/deploy-to-vercel-action). Their respective results were sufficiently similar as to indicate that neither is the cause of the slowness I observed.1

Incidentally, this got noticeably worse after I began “dogfooding” my imgh shortcode for Hugo’s native image processing, rather than using Cloudinary as I’d done for nearly two years. Before switching to imgh, a GHA-based deploy averaged a delta of 28.36% between Vercel and Cloudflare Pages: 63.01 seconds on Vercel vs. 49.08 seconds with CFP. Afterward, that gap jumped to 99.76%, with Vercel coming in at 117.29 seconds and CFP at 58.71.2 (Again, these averages refer to total deploy times. We’ll get more specific shortly.)

Based on the test results:

  • Usually, the Hugo-specific process of each deploy takes under 10 seconds for either Vercel or CFP, so they come out pretty much equal there.
  • In addition, the “runners” for the GitHub Actions seem not to be significant in affecting the respective deploy times.
  • The sticking point for Vercel appears to be in the segment of the deploy wherein it actually publishes the resulting website files to its CDN, and it clearly got much worse after I’d standardized on using imgh and locally hosting all my images.

Protracted “publishes”

If you look at only the “publish” part of each GHA-based deploy, the disparity becomes even clearer. Pre-imgh, the delta between the two providers’ average “publish” times was bad enough at 81.94% (35.74 seconds for Vercel vs. 19.65 for CFP); but, post-imgh, it mushroomed to 295.16% (a whopping 81.73 seconds for Vercel vs. a barely-changed 20.68 for CFP).3 In other words: with imgh in use, each GHA-based deploy took Vercel slightly over one minute longer to publish the site to its CDN than was the case for CFP and the vastly larger Cloudflare CDN.

In case you’re wondering: no, I have no idea whether this has something to do with the fact that Cloudflare owns and operates its CDN’s points of presence (PoPs), while most if not all other Jamstack hosting vendors’ CDNs consist of third-party PoPs. That determination is for others who are much smarter than I — and possess far more inside info.

Here are two charts showing both the pre- and post-imgh “publish” performances for Vercel and Cloudflare Pages. While there are a few spikes here and there, you can see the overall trend of CFP’s substantially outperforming Vercel on both sets of GHA-based “publish” events.

Chart comparing publish-to-CDN times from this site for Cloudflare Pages and Vercel prior to use of the “imgh” shortcode

Chart comparing publish-to-CDN times from this site for Cloudflare Pages and Vercel with use of the “imgh” shortcode

Workarounds for Hugo on Vercel

So, what can you do if your site is on Vercel and you (a.) want Hugo with Dart Sass4 but (b.) also want to regain those swift Vercel deploys that you get without a GHA’s involvement?

I suggest you revert to the standard, non-GHA Vercel process and do one of the following to get Dart Sass:

  • Use the npm sass package. Although doing it that way will result in slower local development (and the dependencies you must add with the use of any Node.js package), it does avoid the problems caused by using a GHA to deploy to Vercel.
  • Use a shell script. It is a little more risky, in that one never knows whether Vercel may later bar its use5, but it preserves the superior dev experience of using Embedded Dart Sass.

The latter method, shell-scripting, is how I’m continuing to use Vercel as this site’s backup host. I’m glad to report that, this way, Vercel is its usual quick-like-a-bunny self again where my deploys are concerned.


CFP build image update?

While I was finishing this post, I saw a GitHub Discussions thread indicating that the Cloudflare Pages build image may get an update. In the comments, I made a pitch for both a better version of Hugo — the current CFP build image uses the ancient 0.54.0, for God’s sake — and the option to specify Embedded Dart Sass through an environment variable, just as one now uses a HUGO_VERSION env var to pull a preferred, um, Hugo version other than 0.54.0. I’ll keep you advised whether there’s any progress on that front; but, as Sidhartha Chatterjee says at the top of the discussion:

This is NOT a definite commitment to what we will deliver.

Still, if that did happen, it would completely eliminate the need for any end runs if you use Cloudflare Pages: you’d use the normal CFP deploy process, and everything would just work.


  1. In my earlier article about all this jazz, I used BetaHuhn/deploy-to-vercel-action within the recommended GHA for Vercel simply because I initially found this particular Action a bit less picky about its configuration, but these latest tests showed amondnet/vercel-action — at least, once I finally got the hang of some of its differences — is perfectly fine for these purposes, too. ↩︎

  2. To keep things fair and maintain meaningfulness for the data, I didn’t count two outliers — i.e., cases of extremely long deploy times on Vercel. One of the outliers almost certainly was due to some oddity on the GitHub side (as nearly as I could tell from the GHA’s log); the other was the first use of imgh, which taxed both Vercel and CFP far beyond the norm for these deploys. ↩︎

  3. In the final GHA-based deploy before I converted the site’s image processing from Cloudinary to imgh, Vercel took 37 seconds of a 71-second total deploy time to publish to its CDN, while CFP took only 15 seconds of a 43-second total to publish. Then, the first time with imgh in place, each service had to suck up all those newly generated images, so the overall deploy times jumped quite a bit: Vercel to 273 seconds and CFP to 214, although the two services’ actual publish times were radically different — 113 seconds for Vercel but only 26 for CFP. ↩︎

  4. And, yes, you definitely want Dart Sass, not Libsass↩︎

  5. Quoting my analogy from the post about using GHAs for this stuff, in which “(A.)” refers to the GHA method and “(B.)” refers to the shell-script method: “It’s kinda like the difference between (A.) getting into a ballpark by buying a ticket and (B.) getting in by sneaking past an overly busy, preoccupied ticket-seller. Either way, you’re inside; but Option A is always suitable, while Option B works only until you get caught. (Okay, maybe that analogy is pushing it somewhat, but you understand what I’m saying.)” I would still urge reading the whole post to get the full context. ↩︎

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