Low Vision Font Tester
Type settings
Simulated conditions
Low vision often reduces contrast sensitivity as well as acuity. Type that is crisp for one reader may blur for another: thinner strokes disappear first, then fine details inside letters, then the whole outline.
The baseline rendering the design was made against.
Low vision often reduces contrast sensitivity as well as acuity. Type that is crisp for one reader may blur for another: thinner strokes disappear first, then fine details inside letters, then the whole outline.
Fine hairlines dissolve; stroke weight and x-height keep letters apart.
Low vision often reduces contrast sensitivity as well as acuity. Type that is crisp for one reader may blur for another: thinner strokes disappear first, then fine details inside letters, then the whole outline.
Light spreads; low-contrast pairs collapse.
Low vision often reduces contrast sensitivity as well as acuity. Type that is crisp for one reader may blur for another: thinner strokes disappear first, then fine details inside letters, then the whole outline.
Everything moves toward mid-grey — the failure mode of light-grey text.
Checks
| Check | Result | Detail |
|---|---|---|
| Size | fail | 16px — below the often-cited 18px large threshold |
| Weight | fail | 400 — thin strokes dissolve first |
| Contrast | pass | ≥7:1 meets AAA body contrast |
| Line length | pass | 66ch within the 45–75 band |
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The low vision font tester applies three visual conditions to the same sample paragraph and grades the type setting behind it. Reduced acuity, glare with its halation, and loss of contrast sensitivity are shown side by side against an unaffected reference, so a face and its spacing can be judged across all three at once.
What is Low Vision Font Tester?
The low vision font tester renders one paragraph four times, once as an unaffected reference and three times under a filtered condition, then grades the underlying type setting on four checks and returns a letter grade.
- Reduced acuity is simulated with a 2px blur, which dissolves fine hairlines first and letter details second.
- Glare and the halation that comes with it are simulated with a light blur, a brightness lift and a contrast reduction together, reproducing the way light spreads and low-contrast pairs collapse.
- Reduced contrast sensitivity is simulated by pulling the whole rendering toward mid-grey, which is the failure mode of light grey text.
- The checks are size at 18px or more, weight at 500 or more, a contrast ratio of 7 to 1 or better, and a measure of 75 characters or fewer.
- Faces come from the built-in catalogue, each shown with its classification so a serif, sans or display face is identified before it is judged.
Weight carries more of the decision here than it does in a general legibility review, because stroke mass is what survives a blur: a 400 weight that reads cleanly at rest can lose its thins entirely under the 2px condition, which is why the check asks for 500 or more. The measure check is deliberately tighter than the usual 45 to 75 character band, capping at 75 on the argument that a reader who is already tracking with difficulty loses their place sooner on a long line. The four checks are scored as a count rather than a weighted composite: four passes is graded A and described as robust, three is a B with one weak point, two is a C to fix before shipping, and one or none is a D. The contrast slider is independent of the simulation filters, which means the ratio can be set to whatever the real design measures and then judged under all three conditions.
- The three conditions are approximations built from CSS filters, not clinical simulations, and they describe the shape of the difficulty rather than a measured response.
- Only one filter applies per pane, so a reader affected by both glare and reduced acuity is not represented in a single rendering.
- The grade counts passes rather than weighing them, so a setting with a failed size and a passed weight scores the same as the reverse.
- Nothing evaluates the palette as a whole, and the colour pair behind the ratio is not shown.
- There is no export: the setting is judged on screen and the values are copied by hand.
The comparison is what makes it useful, because most faces look acceptable under a single condition. Judge the weight first, since that is where the conditions diverge most, then the measure, and treat the size and contrast checks as the two that are cheap to fix. Where the question is specifically about an older readership and a single acuity effect, the font for elderly simulator shows the same problem with a slider instead of presets, the dyslexia font simulator covers the spacing adjustments that help readers who lose their place, and the contrast text checker measures the colour pair that supplies the ratio tested here.
How to use Low Vision Font Tester
- Pick the face from the catalogue and set the size, weight, contrast ratio and measure that the real design uses.
- Read the four rendered conditions in order, comparing the unaffected reference against the blurred, glare and reduced-contrast panes.
- Check the four results in the table and note the grade, then look at which check failed rather than only at the letter.
- Raise the weight first and shorten the measure second, since those are the two values the three conditions punish hardest.
When to use Low Vision Font Tester vs related tools
Use it when a face or a weight is being chosen and the audience includes readers with low vision, when a light-weight brand face is being proposed for body copy, or when a review needs to show why a hairline serif at 300 weight is a poor choice for a long article. It is the only tool here that shows three conditions at once, which makes it the right one for a face decision. For a single condition with a slider, the font for elderly simulator is the closer match, spacing adjustments for readers who lose their place belong to the dyslexia font simulator, and the colour pair behind the contrast figure is measured by the contrast text checker.
Privacy & Security
This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.