Learn French: Une quantité de messages ont rendu cette publication virale. - A quantity of messages made this post viral.

With collective expressions like une quantité de, un groupe de, or une multitude de followed by a plural noun, the verb can often be either singular or plural. Here, it is plural to emphasize the many individual messages acting together, rather than the single collective block of the 'quantity'. If the writer wanted to focus strictly on the volume as a single unit, they could have used the singular a rendu.

Why do we use ont rendu for 'made' instead of a form of faire?

In French, when you 'make' a noun into an adjective (like making a post viral, or making someone happy), you must use the verb rendre. You use faire when making someone or something perform an action, which requires another verb (for example, faire pleurer, meaning to make cry).

The object cette publication is feminine. Why isn't there an 'e' on the end of rendu?

In the passé composé with the helping verb avoir, the past participle only agrees with the direct object if that object is placed before the verb. Because cette publication comes directly after ont rendu, the past participle does not change.

Why is virale feminine?