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Debug tools

The debug tools available for panes contain a wide range of different features to check the quality of your page and the user experience.

You can find the debug tools for each pane by clicking the pen-and-ruler icon above it. If a debug tool is active for the current pane, a blue dot will be displayed.

When a debug tool is active, you can clear it with the "X [debug tool]" button at the top of the popup, or reload it with the "re-apply" button

There are over 40 different debug tools available, ranging from color blindness simulators to text contrast checkers to disabling CSS and JS. Do you have an idea for a useful Debug tool? Let us know.

Polypane is filled with accessibility features. We wrote a full overview on our blog: Find and fix accessibility issues with Polypane.

Overview of all Debug tools

Polypane has over 40 Debug tools and Simulators. Below we list them all.

For more information on them inside Polypane you can hover the icon to the right of each overlay in the popup.

Debug tools

The debug tools give you insight into how your page is built.

Layout Debugging

Quickly find out if elements are where you expect them to be.

Horizontal overflow detection

Elements that cause a horizontal scroll bar/horizontal overflow are highlighted in red, making it easy to spot them. Read more about detecting horizontal overflows.

Contrast checker

Polypane will go through all your text and background combinations and calculate the contrast ratio. All correct ratios are mentioned once, whole the failing ones are all highlighted.

Hover over any of the failing ratios that have an arrow to see the suggested alternative color. You can hover over that suggested alternative color and we'll apply it to the text so you get an instant preview along with the new ratio, or click it to copy the suggested color to your clipboard.

Polypane uses a custom algorithm to determine the ratio that takes the text color, background colors, text shadow, opacities, filters and text-strokes into account when determining the contrast ratio.

Edit content

Edit content makes the entire page editable so you can quickly try out new content and see how it looks.

Polypane automatically turns on spell checking when you're in edit content mode.


The readability debug tool will calculate how difficult each sentence on your page is. Darker, redder sentences are harder to understand while lighter, greener sentences are easier to read. We calculate this using the Automated Readability Index (ARI), which works well for most western, European languages. For pages in Arabic it uses the Automatic Arabic Readability Index (AARI).

If you know of Readability Index formulas for other languages, please contact us.

Content chaos test

Content chaos test will randomly halve, double or triple areas of content so you can check how well your layout handles these situations. Can be used to check if you layout can handle different languages or longer and shorter content.

When active a warning icon is shown next to the pane title, and the entire pane has a red border.

Track Focus

Get a visual highlight of the current focused element that follows the focus as you tab from element to element.

The focus order overlay shows you this information as well, but because the Track focus debug tool is dynamic it's better in handling things like focus traps and interactive pages.

A11y.css third party

A11y.css will highlight any accessibility mistakes and possible risks on your page.

Tota11y third party

Tota11y is an accessibility visualization toolkit with many different features: list headings and links, check labels and simulate screen readers.

Show z-index

Show the z-indices of all visible elements, including if their ancestors have z-indices.

Audible changes

With audible changes, Polypane will sounds a beep whenever the page changes. A nice way to figure out when your page is too busy, or making changes when it does not have to.

Hostile CSS

Hostile CSS will set ugly styles for all your default elements so you can see how well your component styles are isolated.

Disable CSS

Disable CSS will remove all CSS from stylesheets and style attributes on your page. When active a warning icon is shown next to the pane title, and the entire pane has a red border.

Disable JS

Disable JS will disable all JavaScript on a page. This will also prevent much of Polypane's tooling from running, so when this is active a warning icon is shown next to the pane title, and the entire pane has a red border.

Disable Images

Disable Images will hide all images and background images on your page. You can use this to test your email rendering for email clients that block images or to check if your layout doesn't break when images are missing.

Hide Cursor

Hide the cursor in this pane to test keyboard accessibility without cheating.

Placeholdifier third party

Placeholdifier replaces all your content (text, images and videos) with placeholders, so the content of a design doesn't distract from the design itself. inbetween a wireframe and a finished site.


Reachability overlays a color map to show how easy it is to reach parts of the screen. It's calibrated for the mobile device sizes in Polypane and comes in a right hand and left-hand version.

Unneeded scrollbars

Draws scrollbars on the page where they are shown on regular browsers on Windows and Linux (and Mac with an external mouse) but aren't needed.

Target size cursor

Replaces your cursor with a 48 by 48 pixel square so you can measure if clickable elements are large enough and far enough apart.

Elements that are too small and too close together (making tapping them hard) are detected and get a red area surrounding them indicating the space they need.

Detect small text

Detects elements that have small text: 12px for any content, and 16px for form elements (to prevent iOS from zooming in your page).

Text Spacing (WCAG 1.4.12)

Applies the minimum text spacing requirements from the WCAG criterion 1.4.12. Use this to check if any content is lost with these extra settings. Here are the changes it applies:

  • Line height (line spacing) to at least 1.5 times the font size;
  • Spacing following paragraphs to at least 2 times the font size;
  • Letter spacing (tracking) to at least 0.12 times the font size;
  • Word spacing to at least 0.16 times the font size.


Polypane simulates different types of impairments, permanent or situational, that lets you test your pages in different scenarios.

A note on color blindness

We simulate all 8 types of color blindness. Together they affect roughly 1 in 12 men (8%) and one in 200 women in the world.

Between the simulators ending in "*omaly" and "*opia", the "*opia" ones count as full color blindness for that type, while "*omaly" is a milder version, between regular vision and the full color blindness in. It is an average, and people with "*omaly" color blindness can be at any place on that spectrum, so be aware of that.

For more info about the color blindness simulators, read our article Developing for color blindness with Polypane.

Red-green color blindness

The most common forms or color blindness all fall under Red-Green color blindness:





Blue-yellow color blindness

Less prevalent are Blue-yellow colorblindness. 0.02% of the worldwide population has this.



Full color blindness

Full, or near-full loss of color is incredibly rare and affects less than 0.0001% of worldwide population.



Visual impairments

Other visual impairments usually blur or dull someone's vision. As people get older, these become more prevalent.

Cataracts Blurs and clouds vision

Glaucoma (interactive) Blurs vision, especially around the peripheral vision. Use your cursor to bring different parts of the page into focus. The page remains interactive.

Farsightedness Makes it difficult to see details up close.

Astigmatism Blurring and ghosting of the vision in a single direction. Polypane has emulation for horizontal and vertical astigmatism.

Tunnel vision Tunnel vision is the loss of peripheral vision, leaving just the center of your vision. It has a wide range of causes, from permanent (advanced Glaucoma) to temporary (altitude sickness) to situatonal (wearing goggles).

Macular degeneration Loss of central vision.

Bright sunshine

Colors get washed out and low contrast parts of your page become invisible when watching a screen in bright sunlight.

Dimmed Screen

Emulates a desktop screen at 40% brightness or a mobile phone with brightness turned all the way down.

Night mode

Many devices have a night mode, that lowers the blue colors and increases the red colors for a more pleasant display when there is less light.


Dyslexia affects 5 to 10% of the population worldwide, but it might be as high as 17% as not all dyslexia is diagnosed.

There is no single way to simulate dyslexia as it affects different people in different ways. Our simulator makes you aware of the reading difficulty it brings.

Add your own

Do you have an idea for a useful Debug tool? Let us know.


Have a question about Polypane?

Contact us any time though chat, Slack or our contact form:

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