I knew there was a catch regarding the free beer☹️
So, when using that relative width dialog, you’ll get something like:
!https://i.imgur.com/3rZNm2r.jpg!:https://i.imgur.com/3rZNm2r.jpg
But if you just want to make sure it doesn’t break the layout, change it to:
!{max-width: 100%}https://i.imgur.com/3rZNm2r.jpg!:https://i.imgur.com/3rZNm2r.jpg
Yup.
I’m no programmer but it appears that 100% represents 100% of the normal post box width. Big or small.
Here is an example of a pic that is very small but is full post box width….13.8 kb.
Same size image….different percentages.
100%
50%
25%
5%
The important distinction is that max-width won’t stretch the image if the screen is large, while width will.
I’m not sure what you are saying.
See my example above. Choosing the width controls how much of the posting box it fills, no matter what the actual picture size.
It's a shame max-width doesn't seem to be an option if you're using the Advanced Post Editor.
It does, or so djozz said. See the below example at 
a 200% 103% O:) width:
^:)
Edited: reduced the 200% annoyance to 103%. Setting it ridiculously high causes havoc you must know. :-D
Sat, 03/23/2019 - 11:08; Sat, 03/23/2019 - 18:00
So for the “any size” people I should PM them a 335MP 296MB image? (34,485x9741 pixels)
The above is the full sized version of this…
DB…I have a spectacular view like this from my inherited house in the old country. Too bad the house is over a century old and hardly anybody lives in the village.
In fact……where is the picture from?
That photo was taken from just below Nogal Peak looking towards Ski Apache in the mountains just North/Northwest of Alto, New Mexico. It’s actually 43 images at 18MP in 3 tiers, taken with a Canon 7D and 24-105mm lens at 105mm.
I envy you, the view there was breathtaking, my wife and I enjoyed it immensely. The town of Nogal on the North side of Nogal Pass is only 96 people, only even on the map because the Post Office has been there since 1880.
To illustrate max-width, here’s an image of two Emisar D18s. It’s 619px wide, so if you view it on a typical phone, it will be wider than the post panel, or the phone’s screen. Viewed on a desktop, it’s considerably narrower than the space available.
First, with max-width: 100%
And now with width: 100%
Both fill 100% of the space on a narrow screen, but the second is stretched on a wider screen.
I always put 95. I absolutely cannot stand when people ignore scaling their image. Maybe the webmaster can set some kind of default width of 100? That way this catches mistakes. But yeah, I also think it’s painfully negligent and inconsiderate for people to embed images greater than a couple megabytes. 15Mb? That’s OBNOXIOUS.
In my user stylesheet (managed with Stylus) for BLF, I have
img {max-width: 100%;}
which means no image is allowed to be larger than its container. This could be added to the forum CSS.
Nothing to envy….in fact it’s pitiful. It’s in the old country and maybe 10 people live in the village in winter. 100 in the summer. If I don’t pour money into it, it’s going to fall.
Every time i go back, I check up on it, but never slept a night in my life in it. But the view….oh God. It’s feeds the eyes and the soul.
Tell you what, free rent if you fix the roof. Lol
I see no difference in two tablets, one phone and desktop. Turn devices sideways, still nothing.
I agree, and I'll send a link to Mr. Admin so that maybe he can do that for all of us. 
Perhaps they all have screens narrower than about 1180px. Here’s what it looks like with the window wider than that:
4k on desktop
1440 x 2560 phone
Maybe your set up?
+1
This seems like the most universal way to improve things, and should probably be in the default CSS.
Also, I just added this to the script I use to generate the markup for adding images. I had been doing 800px images, but now it’ll do 800px which also scales down on small screens. A normal width=“100%” hint is annoying on large screens, but the max-width method can improve things on small screens without creating extra problems on big screens. 
Short on cash at the moment…can you consume said 1/2 bottle of beer and let me know how refreshing it is??
I can do 3 easy payments of $1.99.