To truncate multiline text in CSS, Safari introduced -webkit-line-clamp a long time ago (first mentions I found date back to 2010).

.line-clamp-3 { /* Required declarations: */ overflow: hidden; display: -webkit-box; -webkit-box-orient: vertical; /* Limit the text block to three lines */ -webkit-line-clamp: 3; }

By now the property has been standardised as line-clamp . Firefox announced that it is also about to support it in Firefox 68, which due July 2019. In said version Firefox will support -webkit-line-clamp ( -webkit -prefixed!), this as per CSS Overflow Module 3 Spec:

For compatibility with legacy content, UAs that support line-clamp must also support the -webkit-line-clamp property.

Neat! But … while testing – using Firefox Developer Edition 68.0b4 – I noticed that Firefox:

Supports only the prefixed -webkit-line-clamp , and not line-clamp Also requires the extra display: -webkit-box; and -webkit-box-orient: vertical; declarations

This feels weird to me … I’d (1) also support the non-prefixed version and (2) would’ve dropped those extra requirements if I were Firefox. I guess this is a direct side-effect of us only having two rendering engines (e.g. WebKit and Gecko) anymore?

The CSS feature for truncating multi-line text has been implemented in Firefox →