In your area, what do/did you call the night before Halloween (when pranksters were often on the loose)? We called it “Mat Night” - residents were encouraged to bring their doormats inside, otherwise they would end up in a tree or some other undesirable location. Back in the 1960s, we would “soap” car windows (write graffiti with a bar of soap - easily removed), or other fairly harmless pranks like ringing doorbells and running away.
When I was a kid, 1960s, suburban Maryland, we did all that on Halloween. There was nothing special happening the night before.
We called it “Tuesday”. (But only when Halloween fell on a Wednesday.) It was a normal day of the year without any pre-holiday activity.
When I was in sixth grade, I remember one kid that rode the same school bus I did tell me as a girl walked by, “See her? On Halloween I’m gonna take a bar of soap and write ‘FUCK YOU’ on her front window!” He seemed proud to share his plan with me. All I could think at the time was “What the hell is wrong with you?” I never understood that sort of pranking. Contrast that with TPing a house, which in my community is how 8th graders flirted with their crushes.
Metro Detroit it’s called Devil’s Night. In the 80s, the city of Detroit would burn that night. It got so bad that local leaders and media tried rebranding it as Angel’s Night, where people would patrol neighborhoods to make sure there was no funny business.
Elsewhere in the area, kids would TP trees or squirt shaving cream on people’s garage doors, etc.
Mischief Night in North Jersey - mild misbehavior was all I recall (and as this was 50 years ago, I don’t remember details)
Mischief night in Philly as well. Some kids called the 2nd night before soap night.
I’ve never heard of any special name for the day before Halloween, and I’ve never heard of any special activities or pranks that occurred on that day.
But if I had to invent a name for it, I’d call it Halloweeneen.
The Night before Halloween… and all through the house, not a creature was stirring, not even a ghost,
As indicated in the classic documentary, The Crow.
[Rated R Movie clip, so note, not safe for work, bloody injuries, language, and criminal behavior]
My youth was mostly in Las Cruces, NM. By my recall, nothing was going on the night before Halloween that wouldn’t have otherwise happened on that night of the week. Though there were some of the usual panicking for last minute costumes, school/friend’s parties, and stocking up on candy.
We called it cabbage night. Sometimes kids would smash pumpkins on the street, but otherwise the mischief was pretty mild. A little soaping of windows and a lot of draping toilet paper over trees.

A little soaping of windows and a lot of draping toilet paper over trees.
Yes, it was called ‘Devil’s Night’ in Metro Detroit, and in the suburbs I grew up in, it amounted to mostly toilet papering residences and soaping windows.
But I always wondered-- why did Devil’s Night pranks (or whatever the regional ‘night before Halloween’ was called) take place before Halloween? The saying is “trick or treat”. Why not determine who was not providing treats and prank them the day after Halloween?

The saying is “trick or treat”. Why not determine who was not providing treats and prank them the day after Halloween?
I wondered the same thing.
Although, i have a friend in Chicago who somehow thought it was a good idea to lecture teenage boys who rang her doorbell too late on Halloween (and hey, maybe she’d already turned off the light). The next day her house was egged, and i gather it was a real pain to wash it off. I wasn’t nearly as sympathetic as i think i was supposed to be when she told me about it.

Mischief Night in North Jersey - mild misbehavior was all I recall (and as this was 50 years ago, I don’t remember details)

Mischief night in Philly as well.
And South Jersey; clearly there is a Mid-Atlantic States linguistic trend here.
Never heard of anything more serious than toilet papering.
We didn’t do anything.
Now I feel like I missed out.
Another South Jerseyite here — we, and most of the Philly ‘burbs, called it Mischief Night. That was when otherwise decent kids turned into toilet-paper commandos armed with soap, shaving cream, eggs, and questionable judgment. Basically our version of The Purge, but with pumpkins instead of machetes and everyone home by ten. Parts of wacky North Jersey called it “Goosey Night,” which sounds less like a prank and more like something you’d have to explain to HR. The tradition supposedly goes back to 18th-century England—proof that teenagers have been perfecting bad ideas for hundreds of years.
Growing up in California, I thought it was a tradition confined to Detroit.
NE MN in the 70s it was called Devil’s Night. The mean boys would go around TPing and egging houses. It fizzled out after a few years.

Metro Detroit it’s called Devil’s Night. In the 80s, the city of Detroit would burn that night. It got so bad that local leaders and media tried rebranding it as Angel’s Night, where people would patrol neighborhoods to make sure there was no funny business.
Grew up in mid-SE Michigan and yes, Devil’s Night. My understanding is it gets really crazy in Detroit. Like, stay down on the floor of your house in case you catch a stray bullet crazy.
I don’t recall anything wild happening in rural Michigan. The kids talked up what they were gonna do, but it never came to anything.