Spoilers are any information that could adversely affect someones enjoyment of the story. If you write a review that contains spoilers on Goodreads, you can hide it by using the hide entire review for spoilers check box at the end of the review. If you only want to hide part of the review you can use the spoiler html tag so that anyone reading it can choose to skip the spoilers or to click on the link to reveal the hidden text.
The format of the spoiler html tag is <spoiler> write spoilers here </spoiler> and the resulting link looks like this: (view spoiler).
To see the html tags that you can use in a review or to verify the format of a tag, click on (some html is ok).
If you see unhidden spoilers in someone else’s review, you can flag it for spoilers, but that takes time because a staff member has to read it and decide if it should be hidden. Making a comment or sending a message to the person asking them to hide their spoilers could be faster. Sometimes people just forget or may not know they can hide only a portion of the review.
- How to Hide Spoilers in Your Blog (brighthub.com)