In the link: https://es.reactjs.org/docs/hooks-reference.html#useref The accent is missing in the word: "código". Where it says: ... "Si quieres correr algún codigo cuando React agregue"... I should say: ..."Si quieres correr algún código cuando React agregue"... Greetings PS: I already opened this issue on another page, but was recommended to open it here. (https://github.com/reactjs/reactjs.org/issues/3604#issue-847242189) Thanks to @eps1lon for that.