Grand Theft Auto Online is full of glitches that players have accidentally stumbled into over the years. While some are useful, like being able to save unsavable outfits or earning more cash that usual, most of them are just mildly interesting.
This latest glitch falls squarely in the second category, allowing you inside Franklin's house from the story mode, which is otherwise inaccessible.
Since GTA Online shares GTA 5's map, with the only differences being the interiors you can access, and a few buildings having changed over the course of six years of DLC, locations from the story are present here too. Franklin's mansion that he gets from Lester during the storyline is among them, but isn't accessible — not with conventional means, anyway.
3671 Whispymound Drive is one of the many luxurious houses in Vinewood Hills and serves as a safehouse for one of the three protagonists. If you've played the story mode, you'll be familiar with the interior already, and getting inside to explore is a lot easier in that mode.
But if you want to check out the house in GTA Online, maybe to hide from attackers, make some cool Snapmatic photos or simply for the novelty and bragging rights, here's how: you need to tip-toe the portion of the wall that faces the street, from where you can carefully walk over to the garage roof.
From the garage roof, you can access the roof of the house proper, as seen in the video from this Reddit post. Once on the roof, use any explosive weapon to fire into the ground right in front of your character, causing you to be caught in the blast.
https://www.reddit.com/r/gtaonline/comments/gh6sm4/clipping_into_franklins_house_in_online/
Blind luck willing, when your character falls back onto the roof, you'll clip through it into the house. It might require a few tries to pull off, and you can't easily get out either. Nothing in the house is interactable either, so don't expect huge payoff for getting in.
