Whoosh vs Plug in Speed: what does each app speed up?

You sell a canvas tote, and two speed apps want the job

You sell a natural canvas tote with long cotton handles. It’s the product most people land on, and its page feels slow when you open it on your phone, so you searched the Shopify App Store and found two speed apps that sound alike: Plug in Speed and Whoosh.

They work on different things. Plug in Speed works on the files behind the tote page, meaning the photo you uploaded and, on two of its plans, the theme’s code. Whoosh works on the order things arrive, so the tote photo shows up before your popup, chat, and reviews. We make Whoosh, so read the table with that in mind.

So Plug in Speed vs Whoosh comes down to a question you can answer on your own phone. When the tote page opens, is the photo slow because its file is big, or because something else got to the screen first?

What each app does to the tote page

Let’s start with what Shopify already does, because it’s more than most people expect. When a shopper taps the tote, Shopify doesn’t send them the full photo you uploaded. It keeps that file and makes a smaller copy for their screen, and when the phone can show a lighter kind of file, it gets that instead of the JPEG. Shopify’s image guide names those lighter files WebP and AVIF, and says you do not need to shrink the photo before you upload it.

The theme’s code travels the same way. The CSS sets how the tote page looks, and the JavaScript makes the photo gallery swipe. Taking the gaps and notes out of those files leaves less to download, which people call minification, and Shopify’s platform docs say the files it sends are already minified and compressed on the way to the phone.

Plug in Speed works one step earlier, on the file sitting in your admin. The Plug in Speed Shopify app, listed as Plug in Speed - SEO Page Speed by the developer Plug in Useful, compresses that stored tote photo, which means rewriting it as a smaller file.

Its App Store listing offers two kinds. Lossless keeps every detail and saves less, while lossy drops detail you’re unlikely to notice and saves more, and the listing mentions 30-day backups.

On the Standard and Premium plans, Plug in Speed also minifies the theme’s CSS and JavaScript itself. The Free and Lite plans compress images only, and the listing also describes a speed dashboard that shows your average load time.

Now Whoosh, which leaves the tote photo file and the theme’s code alone. When the tote page opens, your other apps start loading too: the email popup, the chat bubble, the review stars, each one a small program from another company.

Whoosh holds those programs back until the tote photo is on screen, then lets them run, so the popup still asks for an email.

To show whether sales moved, it splits your visitors 50/50, half with Whoosh on and half without, and compares sales.

Here’s the same thing side by side.

Why a smaller tote photo can still lose to the chat bubble

Here’s the awkward part. Compressing the tote photo doesn’t change when your chat bubble shows up, because a smaller file and a later popup are two different fixes, and neither app does the other one.

I know what you’re thinking. You already installed Plug in Speed, ran it over every photo, and the tote page still feels slow. If the chat bubble’s program started before the tote photo yesterday, it starts before it today, because a lighter file doesn’t change which program the phone runs first.

That cuts the other way too, and this is where Plug in Speed is the better buy. If the tote photo in your admin is the full-size original off the camera and you want it smaller, Whoosh won’t touch it. Plug in Speed will, and its free plan covers 40 images a month, so you can try the tote before you pay anything.

Just know what you’re buying. Shopify still makes the phone’s copy from that file, so the shopper was already getting a smaller photo than the one in your admin, and the app’s main change is to the file you store.

The theme’s code is the other reason to pick Plug in Speed, and only on Standard or Premium. If a developer or a speed report has pointed at your theme’s CSS and JavaScript, those two plans minify it, and Free and Lite don’t.

Before you upgrade only for that, Shopify’s platform docs say the files it sends are already minified and compressed. Plug in Speed’s minify, on Standard and Premium, is a second pass on the theme’s own code.

Whoosh is the buy when the photo file is fine and something else gets there first. A signup popup covers the tote, the chat bubble pops up, or the review stars load while the photo is still blank. Whoosh doesn’t compress images or minify code, so it isn’t a replacement for Plug in Speed either.

Can the two share a store? Yes, because one works on files and the other works on timing. After you install either one, open the tote on your phone and tap the popup, the chat, and Add to cart, so you know each of them still works.

Open the tote on your phone, then find its photo in Plug in Speed

Two looks at one tote. Start with the phone, because that’s the one a shopper sees.

Open the tote’s live product page on your phone, using the link a shopper would tap, in a private tab so nothing is remembered from your last visit. Watch the first few moments closely. Does the tote photo arrive first, or does a signup popup, a chat bubble, or a row of review stars get there before it?

If it happens too quickly to call, record your screen while the page loads and play it back slowly. You’re only looking for one thing, which is whatever reaches the screen before the canvas tote does.

Now open Plug in Speed in your Shopify admin and find the tote photo in its image list. Has that file been compressed yet, or is it still the original you uploaded? If you haven’t installed the app, the free plan is enough to run this one photo through it.

If a popup or chat beat the tote photo, that’s Whoosh’s job, and the plans are in the table above. If the photo came first but slowly, and the stored file was still the original, that’s Plug in Speed’s job. What an image optimizer app does on Shopify explains which copy of the photo an app like that changes.

If neither showed up, and the wait was a white screen before anything appeared, neither app is aimed at it. The speed app comparison matches that wait to the apps that clear it.

If you saw both, compress the tote photo first, since the free plan costs nothing to try, then deal with the popup. Either way, do the two looks before you install anything, because whichever one you actually saw on the tote picks the app.