structure - Where should I put my tl;dr?

By definition

TL;DR, short for "too long; didn't read", is Internet slang to say that some text being replied to has been ignored because of its length. In slang it can also stand for "Too lazy; didn't read". It is also used as a signifier for a summary of an online post or news article.
Wikipedia

Usually the author of a long post gives a tl;dr, a summary of the what the post about in a short paragraph or sentence. This can be put before the post begins, or the after.

tl;dr We are asking you to start saving water and electricity for the sake of our environment.

Blahblahblah...

I've seen two types of people, who scrolls down to see the tl;dr, and those who looks for the summary on the top of the post. This makes me unsure where to put my post summary. If I were to write a post, a letter, etc. how can I decide which position is the most beneficial to me, i.e avoid people skipping my question entirely and getting the message across.

tl;dr How can I decide that putting my tl;dr at the top of the post, or bottom, will benefits me the most? What factors should I consider?

I'm thinking more about the types of the post: informational post might be better with bottom summary, while question better with top summary. What other factors affecting this?

Note: Some put a notification at top of the post, informing a tl;dr is available at the bottom of the post.

Answer

Where to put the a tl;dr or summary is going to vary depending on the piece.

For example, an email from I.T. warning about a change will include the most important information and what users need to do upfront, and then may include further details beneath that for those who are curious.

Having the tl;dr at the beginning means people are more likely to see it.

In other pieces of writing it makes more sense to have it at the end. For example, someone sharing a story might include the tl;dr at the end to avoid spoiling anything for someone reading the whole thing.

tl;dr If the tl;dr is important information, put it at the top. If it's for convenience, put it at the bottom.