"Bringing Left 4 Dead into your marketing mix also brings in the expectations of Left 4 Dead, thus opening yourself up to a lot more criticism." -Adam Sessler (G4TV)

All B4B gameplay is patched and recorded post-launch.
All L4D1 clips have been recorded on the original L4D.
Thumbnail, Francis intro, and 20∶35 were made in Garry's Mod.

L4D1 modding tools released six months after launch: www.l4d.com/blog/post.php?id=2510
L4D2 modding tools released one month after launch: www.l4d.com/blog/post.php?id=3286

——— Interviews ———
Game Informer    • Life After Death: The History of Turtle Ro...  
thegameawards    • Back4Blood World Premiere Trailer and Game...  
IGN    • Left 4 Dead - New Survivors Trailer  
TheWeeklyBlend    • Left 4 Dead Interview  
Game Informer    • Back 4 Blood Dev On PVP, Microtransactions...  
IGN    • Back 4 Blood Dev Interview: Breaking Down ...  
Gamespot    • Left 4 Dead 2 - Gabe Newell Interview at G...  
GameTrailers    • Left 4 Dead Story and Undead Playability I...  
G4TV    • G4TV Hands On: Left 4 Dead E3 2008  

——— Ending sources ———
Mega64    • Mega64: The Beatles Rock Band  
IGN    • Left 4 Dead Xbox 360 Interview - Kerry Davis  
Techniche    • Techniche Interviews'17 : A Conversation w...  
Gamereactor    • TGS09: Left 4 Dead 2 interview  
GDC    • Valve's Physics for Game Programmers  
GameTrailers    • Left 4 Dead - GTTV Extended Preview  
Steam Dev Days 2014    • Data to Drive Decision-Making (Steam Dev D...  
IGN    • Valve on the Future of Half-Life Plus Othe...  
GDC    • AI-driven Dynamic Dialog through Fuzzy Pat...  
Inside Xbox    • 東京ゲームショウ 2009 『Left 4 Dead 2』インタビュー (TGS 2...  
Esports in a Nutshell    • Valorant Art Director Moby Francke talks A...  
LICAF    • Bay Raitt Interview  

——— Mods at 22∶30 ———
Common Madness steamcommunity.com/sharedfiles/filedetails/?id=911…
Cat Gun steamcommunity.com/sharedfiles/filedetails/?id=827…
Nick Dimmadome steamcommunity.com/sharedfiles/filedetails/?id=257…
Chef Coach steamcommunity.com/sharedfiles/filedetails/?id=118…
Fall Guys steamcommunity.com/sharedfiles/filedetails/?id=222…
Halloween Rochelle steamcommunity.com/sharedfiles/filedetails/?id=225…
Shirtless Ellis steamcommunity.com/sharedfiles/filedetails/?id=157…
LOTR Campaign steamcommunity.com/sharedfiles/filedetails/?id=245…
Space Skyboxes steamcommunity.com/sharedfiles/filedetails/?id=157…
Halo Online HUD steamcommunity.com/sharedfiles/filedetails/?id=797…
M9 Bazooka steamcommunity.com/sharedfiles/filedetails/?id=880…
TR Survivors steamcommunity.com/sharedfiles/filedetails/?id=152…
Halo 3 M90 Shotgun steamcommunity.com/sharedfiles/filedetails/?id=151…
Halo 4 Energy Sword steamcommunity.com/sharedfiles/filedetails/?id=249…
Chicken Pipebomb steamcommunity.com/sharedfiles/filedetails/?id=507…
Overwatch Skies steamcommunity.com/sharedfiles/filedetails/?id=172…

——— Songs ———
L4D - Menu Theme    • Left 4 Dead - Menu Theme  
L4D2 - Dead Center    • Left 4 Dead 2 Soundtrack - 'Dead Center'  
L4D - No Mercy Theme    • Left 4 Dead - No Mercy Theme  
HL2 - Triage At Dawn (slowed)    • Half-Life: Alyx - Final Hours - Triage At ...  
L4D - The Monsters Within    • Left 4 Dead Soundtrack- 'The Monsters Within'