What Is a Reading Ruler? How a Line-Focus Overlay Helps You Track Text

If you’ve ever lost your place halfway down a long article, re-read the same line twice, or skipped one entirely, you’ve run into a plain visual tracking problem — not a comprehension one. A reading ruler is a small tool built specifically for that problem: it highlights the line you’re on and dims everything around it, so your eyes always have one obvious place to land.

What a reading ruler actually is

A reading ruler (also called a line-focus overlay, reading guide, or reading strip) is a band that sits over a block of text and marks out the current line, while dimming the lines above and below it. As you move down the page, the band moves with you.

This isn’t a new idea — it’s a digital version of a much older habit. Holding a ruler, an index card, or a finger under a line of text while reading is a technique teachers, tutors, and vision specialists have used for a long time to help readers track lines without losing their place. A digital reading ruler does the same job automatically, on any webpage, without you having to hold anything against the screen.

Who a reading ruler helps

Losing your place while reading has a few different causes, and a reading ruler addresses the visual-tracking part of most of them:

• ADHD and attention tracking. If your eyes drift off a line when your focus breaks and then have trouble finding where you left off, a highlighted band gives you an unambiguous anchor to return to. This pairs with the visual-anchoring approach behind Bionic Reading and other ADHD reading strategies — both are aimed at the same underlying problem of sustaining visual attention across long text.
• Dyslexia and other reading differences. Dense, tightly packed text can make it easy to drop down to the wrong line or re-read the one you just finished. Narrowing the visual field to one line at a time reduces how much text is competing for attention at once.
• Low vision. Dimming everything outside the current line increases the effective contrast between what you’re reading and the rest of the page, which can make the active line easier to isolate on busy or cluttered layouts.
• Long, dense reading sessions. Legal documents, technical manuals, and other unusually long or unfamiliar text are exactly where line-tracking mistakes compound — a reading ruler keeps a fresh, low-effort visual anchor in place for the whole session, not just the tricky parts.

How ReadEase’s Reading Ruler works

ReadEase’s Reading Ruler adds a highlighted band that follows your cursor as you move it down the page, dimming the page above and below the band. Because it tracks your mouse position rather than requiring you to scroll in fixed increments, it works the same way on an ordinary long article as it does on a page you’re scrolling quickly through — there’s nothing to set up per page.

Three things are adjustable, so the tool can match how you’re reading rather than forcing one fixed look:

• Band thickness — from a narrow strip for tracking a single line closely, up to a wider band that comfortably covers two or three lines at once.
• Band color — the highlighted band’s color, so it stands out clearly against the site’s own background and text color.
• Dim strength — how strongly the rest of the page is dimmed, from a subtle fade up to a much darker background that leaves the band as the only clearly visible thing on the page.

Setting it up

1. Install ReadEase, a free Chrome extension.
2. Open the Focus panel and turn on Reading Ruler.
3. Set Band thickness — start narrow if you want to track one line precisely, or widen it if you read a line or two ahead as you go.
4. Pick a Band color that contrasts clearly with the page you’re reading.
5. Adjust Dim strength — light dimming keeps the rest of the page loosely visible for context; a stronger setting removes almost all distraction from everything outside the band.

Once it’s on, just move your cursor down the page as you read — the band follows automatically, on any site, with no need to reconfigure it each time you open a new tab.

Combining it with other reading tools

A reading ruler solves a tracking problem; it doesn’t address text density or font legibility on its own, so it tends to work best alongside a couple of other adjustments:

• Line height. A taller line height gives the ruler’s dimming more room to visually separate the current line from its neighbors, which reinforces the same effect from a different angle.
• Font choice. If crowded or unfamiliar letterforms are part of what’s making text hard to track, pairing the ruler with a clearer font — including dyslexia-friendly options — addresses both problems at once rather than just one.

None of these tools require picking just one. Turning on the Reading Ruler alongside a comfortable line height and font takes a few seconds and, once set, applies automatically the next time you open a browser tab.

Frequently asked questions

Does a reading ruler slow down reading?

For most people it doesn’t, since it doesn’t change how you scroll or where you click — it just adds a visual highlight that follows your existing cursor movement. Some readers find the dimming itself briefly noticeable when they first turn it on, but it stops being distracting once the band is tracking naturally with their reading pace.

Is a reading ruler the same thing as Bionic Reading?

No. Bionic Reading changes the text itself, bolding the leading letters of each word to create fixation points. A reading ruler doesn’t touch the text at all — it overlays a highlighted band and dims everything else, which targets losing your place on the page rather than how each word is processed. They solve related but different problems and work fine together.

Will a reading ruler work on any website?

Yes — because it’s an overlay that tracks cursor position rather than something built into a specific page, it works the same way on ordinary articles, documentation, and long-form content generally, without needing the page to be structured any particular way.

What if the highlighted band is distracting instead of helpful?

Turn dim strength down for a lighter effect, or widen the band thickness so it covers more of the paragraph at once and feels less like a spotlight. If it still isn’t a fit, it’s fine to leave it off and rely on other adjustments, like increased line height or letter spacing, instead.