SC 1.4.12 and Flutter

[JuliaTol-properaccess]

Hej allihopa,

Does anyone here have experience testing Flutter web applications?

I’m looking for input on how WCAG SC 1.4.12 (Text Spacing) should be interpreted for Flutter-based websites.

In my experience, Flutter web applications do not respond to text spacing adjustments as described in SC 1.4.12. The rendered output in the browser is not exposed as typical HTML content; instead, the entire interface is rendered within a single element.

Unlike traditional HTML-based websites, Flutter does not inherit or respond to text rendering styles from the parent document’s CSS. As a result, user-applied CSS overrides for line height, letter spacing, word spacing, or paragraph spacing have no effect.

Based on this rendering model, is it reasonable to conclude that SC 1.4.12 is not applicable to Flutter web applications, or should it be evaluated differently than for HTML content?

I’d be interested to hear how others approach this in audits or conformance testing.

[patrickhlauke]

if the technology doesn't allow users to change the text spacing metrics, then the SC is not applicable

[Nojaid-Ad]

Flutter Web renders text inside a canvas-based or single DOM element model rather than exposing semantic HTML text nodes. Because of this, user-applied CSS text spacing overrides (line-height, letter-spacing, word-spacing) do not reliably affect Flutter-rendered content in the same way they do for traditional HTML.

According to WCAG 2.1 – SC 1.4.12 (Text Spacing), the success criterion applies only when users can override text spacing via user agent or author stylesheets. If the underlying technology does not support user modification of text spacing, then the SC is not applicable, rather than a failure.

For Flutter Web specifically:

Text is not exposed as standard HTML content

Parent document CSS overrides do not propagate into Flutter’s rendering layer

Therefore SC 1.4.12 cannot be meaningfully tested using traditional CSS overrides

In accessibility audits, Flutter Web implementations are typically:

Documented as Not Applicable for SC 1.4.12, or

Evaluated based on Flutter-level text configuration (e.g., default line height, font scaling) rather than external CSS manipulation

Unless Flutter explicitly exposes text spacing controls to user agents, treating SC 1.4.12 as not applicable is a reasonable and standards-aligned conclusion.

Let me know if you are applying a specific accessibility testing methodology (e.g. WCAG-EM or EN 301 549), as interpretations may vary slightly.

[JuliaTol-properaccess]

Thanks, colleagues — this matches my understanding.
That said, I’m wondering how you interpret clause 11.7 of EN 301 549, which says:

Where software is not designed to be isolated from its platform, and provides a user interface, that user interface shall follow the values of the user preferences for platform settings for: units of measurement, colour, contrast, font type, font size, and focus cursor, unless these are overridden by the user.

Would you agree that a website built using a canvas-based framework could still be WCAG-compliant, but that a mobile app showing those same pages inside web views would not comply with EN 301 549?