Quick answer: a lightweight reading time plugin should add only a few kilobytes to a page, avoid loading any external library, calculate the word count once and cache it rather than recalculating on every load, and stay out of the way of page caching plugins entirely. Below is how to actually test for this yourself, a worked comparison of what the numbers look like in practice, and what tends to separate a lean plugin from a bloated one.
Why plugin weight matters more than it seems
Reading time is a small feature. It’s a number and maybe a progress bar. There’s no reason it should meaningfully affect page load, yet plugins in this category vary widely in how much they add to a page. Some ship a full JavaScript library to animate a bar that could be done in a dozen lines of vanilla CSS and JS. Some run a database query on every single page load to fetch settings that never change. Some don’t work correctly with page caching at all, meaning the reading time gets frozen at whatever it was when the page was first cached, even after you edit the post.
None of this is necessary for what the feature is actually doing. That gap between what’s needed and what gets shipped is where performance problems come from.
How to test a plugin’s actual weight yourself
You don’t need to trust a plugin’s marketing copy. You can check this directly:
- Open your browser’s developer tools (F12 in most browsers) and go to the Network tab.
- Load a post on your site before installing any reading time plugin, and note the total page weight and number of requests.
- Install and activate the plugin, then reload the same post with the cache cleared.
- Compare total page weight and request count. A lightweight plugin should add a small handful of kilobytes and at most one or two extra requests, usually just its own script and stylesheet file.
- Filter the Network tab by JS to see exactly what the plugin loaded. If you see a request to an external CDN, or a script larger than roughly 20-30kb for what is a reading time and progress bar feature, that’s worth questioning.
You can also run a PageSpeed Insights test before and after activation. A well-built plugin shouldn’t move your score at all. If your score drops noticeably, something in the plugin’s implementation is doing more work than the feature requires.
A worked comparison
Say you test three reading time plugins on the same 1,200 word post, cache cleared each time, using the Network tab method above. A minimal, well-built option might add one CSS file around 1kb and one JS file around 2kb, both loaded only on single posts, for a total addition of roughly 3kb and two requests. A mid-weight option might bundle a small animation library for the progress bar, adding 15 to 20kb and pulling in a Google Fonts request for a custom badge icon, for a total closer to 25kb and four requests. A heavier option, often one marketed as an all-in-one engagement suite, might load its script and styles site-wide rather than only on posts, add a tracking pixel for its own analytics dashboard, and total 60kb or more across five or six requests, including some on pages that never even display the reading time feature.
None of these numbers are enormous on their own, but they compound. If your site already runs a few plugins in that mid-to-heavy range for other features, each one seeming small individually, the total adds up to a genuinely sluggish page. The Network tab test matters precisely because it’s the only way to see which category a given plugin actually falls into, rather than guessing from its settings screen or its listing page description.
What actually separates lightweight from bloated
- No external libraries. A progress bar is a colored div that changes width on scroll. It doesn’t need a full animation library to do that.
- Cached word counts. The plugin should calculate reading time once when a post is saved and store it, not recalculate it from raw content on every single page view.
- Cache-plugin compatibility. If you run a page caching plugin like WP Rocket or W3 Total Cache, the reading time plugin’s output needs to work correctly with a cached HTML page, not rely on a database call that a cache would bypass and leave stale.
- Scoped loading. Scripts and styles should only load on post types where the feature is actually enabled, not on every single page of the site including your Contact page and cart page.
- Passive scroll listeners. The JavaScript driving a progress bar should use passive event listeners so it doesn’t block scroll performance, particularly noticeable on mobile.
Red flags to watch for
- A settings screen with dozens of options for a feature this simple, often a sign the plugin is trying to be a broader content-engagement suite rather than doing one thing well.
- Analytics or tracking scripts bundled in that have nothing to do with reading time itself.
- An admin notice pushing you toward a premium upgrade before you’ve even configured the free version.
- No mention of caching compatibility anywhere in the plugin’s description, which usually means it wasn’t considered during development.
- Assets loading on every page type instead of only where the feature is enabled, visible immediately in the Network tab test on a page like your cart or checkout screen.
The trade-off with feature-heavy plugins
To be fair, some heavier plugins offer things a lightweight one won’t: reading time by category, integration with content-engagement dashboards, or estimated reading time shown in multiple languages automatically. If you genuinely need those things, the extra weight might be a reasonable trade. But most sites installing a reading time plugin just want the number and maybe a progress bar, and paying a performance cost for features you’ll never open in the settings screen isn’t a good trade.
Where ReadyGo Reading Time fits
ReadyGo Reading Time is a free plugin built specifically around the lightweight, cache-safe criteria described above: no external libraries, cached word counts instead of per-load recalculation, and scoped script loading so it doesn’t run on pages where the feature isn’t enabled. It’s not trying to be a full engagement suite, it’s built to do the reading time and progress bar job and stay out of the way otherwise. Since it’s free, it’s easy to run the Network tab test above yourself and compare it against whatever you’re currently using.
FAQ
How much page weight is actually acceptable for this kind of feature? As a rough guideline, anything under 5kb combined for CSS and JS, loaded only on the post types where it’s enabled, is a reasonable target. Above 20-30kb, you’re paying for more than a reading time badge and progress bar, even if the plugin’s marketing frames it as lightweight.
Does a heavier plugin necessarily mean a worse score on PageSpeed Insights? Not always directly, since PageSpeed weighs render-blocking resources and layout shift more heavily than raw file size. But heavier plugins are more likely to introduce both of those problems, so the correlation is real even if it isn’t one-to-one.
Should I worry about this on a small blog with low traffic? Page weight affects every single visitor’s experience regardless of your traffic volume, and it’s also a search ranking factor independent of how many people are hitting your site. Low traffic doesn’t make a slow page acceptable, it just means fewer people notice.
Can I measure this without developer tools experience? Yes. PageSpeed Insights and GTmetrix both give you a plain-language before-and-after comparison without needing to read raw Network tab data, though the Network tab method gives you more specific detail about exactly what a plugin is loading.
Wrapping up
Reading time plugins shouldn’t be a performance decision you have to think hard about. Run the developer tools test described above on any plugin before you commit to it, check for the caching and library red flags, and pick the option that adds the least weight for the feature you’re actually trying to add. It’s a small feature. It should behave like one.