Accessibility

OSCharts is built so that everyone gets the same information from a chart, however they read it. This page says what each chart does and how we check it.

What every chart has

• A title and a plain-language summary written from the data: highest, lowest, first, last, totals and changes. Nothing in the summary is a guess.
• The data table, with proper column and row headers. It is in the page from the start; with JavaScript on, a Data table button shows and hides it. It always prints.
• Keyboard exploration. Tab to the chart, then the arrow keys move from value to value and a screen reader speaks each one, with its position (“3 of 12”). Up and down switch series. Home and End jump to the ends. Escape leaves.
• Hover and touch show the same words in a tooltip.
• Identity never by color alone. Every series has its own marker shape or texture. Textures are on from the start wherever filled marks would otherwise differ only by color; the Patterns button turns them off or on for every chart and remembers your choice. They are always on in print and in Windows high-contrast mode.
• Color contrast. Every series color is at least 3:1 against the chart background in light and dark themes, and neighboring colors stay apart for the common kinds of color blindness.
• Sound. Play as sound plays each value as a tone, higher for larger values, moving left to right.
• Any screen. Charts are redrawn at the real width, so text stays readable on a phone and at 400% zoom. With JavaScript off, a narrow layout is used on small screens.
• Print. Black text on white, textures on, the data table printed under the chart.
• Your settings. Dark mode, reduced motion and forced colors are all respected.
• Downloads as CSV, SVG and PNG. The SVG carries its own title and description.

How we check

Every change runs an automated walk-through of every chart on this site: the axe-core WCAG 2.2 AA checks at desktop and phone widths, the keyboard readout, print, forced colors, and the page with JavaScript off. The tests are in the source repository.

What we haven't done yet

Automated checks can't tell how a chart feels with a real screen reader. Testing with NVDA, JAWS, VoiceOver and TalkBack users is planned and not done yet. If something doesn't work for you, please write to accessibility@oscharts.com.