Automatic text replacement [substitution], space to replace
It depends on how you have the global pref &amp; also the prefs in each app...

Bear in mind there are 2 ways to trigger it - whether you have "Correct spelling automatically" set or not

Of course, you need Text replacement on, in for instance, Safari > Edit > Substitutions



but then if you also have
Edit Menu > Spelling &amp; Grammar > Check Spelling While Typing and also Check Spelling Automatically  


then as you start to type a substitution, it will first auto-suggest underneath

As soon as it auto-suggests, you have 2 options...  


Hit  Enter ⌅  &amp; it will auto-fill &amp; add a space, or  
Hit  ↓  then  Enter ⌅  &amp; it will not leave a space


The real down-side of having it set like this is if you're not expecting it to correct something &amp; it does, without you noticing.
Any slightly unusual word or spelling can get auto-corrected to a simpler... yet wrong one, if you don't proof-read.  

Your friend Anny quickly becomes Any, for instance