This is an ongoing list detailing all films available on the OFFICIAL YouTube Movies channel under 'Free-to-watch'. I refer to the official playlist as reference.
To be updated daily.

Don't worry, Letterboxd team, they're completely legal. Please don't take this down like you did on 27 July 2020 for Full movies on Youtube!

Note: Check the links in the Notes. Use a VPN if you're outside U.S. and can't load the films!

(Yeah, I know, most of these are awful, but sort by rating/popularity and you'll likely see the best ones)

NOT ON LETTERBOXD:
Led Zeppelin: Dazed and Confused (2012) Amazon
Illustrated: A Vans BMX Video (2016) Amazon
Fun with Slime: Part 1 (2019) Amazon
Fun with Slime: Part 3 (2019) Amazon
Ernest's Greatest Hits Volume 1 (1986) Amazon
RWBY: Volume 1 (2013) IMDb
RWBY: Volume 2 (2014) IMDb
RWBY: Volume 3 (2016) IMDb
RWBY: Volume 4 (2017) IMDb
RWBY: Volume 5 (2018) IMDb
Beyoncé: Fierce and Fabulous (2014) Amazon
The Last 24 Hours: Amy Winehouse (2019) Amazon
Nostradamus: Future Tense (2020) IMDb
The Diana Story: Part I: The Young Princess (2017) Amazon
The Diana Story: Part II: Broken Hearts (2017) Amazon
Diana: The Royal Truth (2017) Amazon
The Great Outdoors: Eleven (2018) IMDb
Elvis & The Memphis Mafia (2018) IMDb
509 Films: Volume 11 (2016) 509
Lil Wayne: Rap Sheet (2013) Amazon

NEW ARRIVALS:
Lo and Behold: Reveries of the Connected World (2016), The Image Revolution (2013), Capitalism: A Love Story (2009), The Pastor's Daughters (2016), Guardians (2017), Dior and I (2015), Tracks (2013), Love Won't Let Me Wait (2016), Iceman (2014), Missing 411: The Hunted (2019), Paper Angels (2014), Raging Bull (1980)

NO LONGER ON PLAYLIST BUT STILL AVAILABLE (incomplete list):
Alcatraz (2018), Ephraim's Rescue (2013), Freddie Mercury: The King of Queen (2018), Grace of Monaco (2014), Police Story: Lockdown (2013), Princess Caraboo (1994), Southern Comfort (1981), The Monkey King (2014), The Suspect (2013), 8 Assassins (2014), Barabbas (1961), Dakota's Summer (2014), Digimon Adventure tri. Part 1: Reunion (2015), Hollow in the Land (2017), There Be Dragons (2011), Christmas Cottage (2008), 4 Minute Mile (2014), Abandoned (2010), Christmas Trade (2015), The Yellow Handkerchief (2008), Tortilla Soup (2001), Vendetta (2015), What Maisie Knew (2012), Chasing the Storm 2 (2017), Mountain (2017), Ragamuffin (2014), Some Like It Hot (1959), The Atticus Institute (2015), The Jackie Robinson Story (1950), Shoot First: A Cop’s Vengeance (1991), Bridge of Dragons (1999), Kristy (2014), One Direction: The Inside Story (2014), Task Force: Caviar (2000), Battle of Kings: Bannockburn (2014), Digimon Adventure tri. Part 6: Future (2018), Sacrifice (2011), Toonstone (2015), Craig Ferguson: A Wee Bit o’ Revolution (2009), Rufus (2013), Lost in Hong Kong (2015), Mafia (2011), Residente (2017), The Strange Ones (2017), The Survivor (1998), Alex & the List (2018), Badges of Fury (2013), Christmas Story (2007), Digimon Adventure tri. Part 5: Coexistence (2017), Minecraft: Into the Nether (2015), Impasse (1969), Evil Alien Conquerors (2003), From Within (2008), American Terrorist, Borrowed Hearts (1997), Salt & Pepper (1968), The 39 Steps (1935), Back in Time (2015), Beyond Sherwood Forest (2009), Kung Fu Yoga (2017), Shattered (1991), The Pride of the Yankees (1942), Drug War (2012), Drug War (2012), Ernest Goes to School (1994), Joseph and Mary (2017), Merry in-Laws (2012), Shade (2003), The Dirty Dozen: The Deadly Mission (1987), The Family Fang (2015), The U.S. vs. John Lennon (2006), Hans Christian Andersen (1952), Mirage Men (2013), The Winslow Boy (1999), The Family Fang (2015), Digimon Adventure tri. Part 4: Loss (2017), Finding Noah (2015), Frailty (2001), Kenny Rogers as The Gambler (1980), Scorched (2003), The Secret Life of Walter Mitty (1947), Wu Dang (2012), If I Were You (2012), Kung Fu Jungle (2014), New World (2013), Prodigy (2017), The Wave (2015), A Kind of Murder (2016), Black Christmas (1974), Christmas for a Dollar (2013), Christmas on Salvation Street (2015), Journey to the Christmas Star (2012), King of California (2007), Knuckleball! (2012), Nosferatu the Vampyre (1979), Special ID (2013), The Assassins (2012), The Fighting Preacher (2019), The Mighty Quinn (1989), The Truth About Emanuel (2013), Thin Ice (2011), Thsi Beautiful Fantastic (2016), A Royal Night Out (2015), Men with Brooms (2002), Rocky Marciano (1999), Stranded (2001), The Thieves (2012), A Frosty Affair (2015), Affliction (1997), Any Day (2015), Railroad Tigers (2016), The Timber (2015), The Best of Times (1986), Christmas Crush (2012), Love Trap (2005), The Gate (1987), Island of Fire (1990), American Pastoral (2016), Away from Her (2006), FIshing Naked (2015), The Birdcage (1996), The Proud Rebel (1958), Warriors of Heaven and Earth (2003), Barquero (1970), Christmas Coupon (2019), Diary of a Tired Black Man (2009), Gift of the Magi (2010), Plato's Run (1997), Red Lights (2012), Stock Option (2015), The Adventurers (2017), The Lords of Flatbush (1974), 1911 (2011), Windfall (2002), Food, Inc. (2008), Lil Wayne: Bling (2018), The Dinner (2017), What We Did on Our Holiday (2014), A War (2015), Almost Friends (2016), Ambush Bay (1966), Apartment 1303 3D (2012), Avenging Angelo (2002), Bernie (2011), Chocolate (2008), City of Fear (2000), Danika (2006), Dudes & Dragons (2015), H8RZ (2015), I'll Follow You Down (2013), Kung Fu Jungle (2014), Lavalantula (2015), Marilyn Hotchkiss’ Ballroom Dancing & Charm School (2005), Moto 6: The Movie (2014), Mountain Patrol (2004), Nancy (2018), Painted Skin: The Resurrection (2012), <<a href="https://www.youtube.com/watch?v=JkPtiZ5y17Y">Rapid Exchange (2003), SLAY: The Axell Hodges Story (2017), Shark Attack (1999), Shark in Venice (2008), Synchronicity (2015), The Fitzgerald Family CHristmas (2012), The Hot Flashes (2013), The Visit: An Alien Encounter (2015), Top of the World (1998), Very Good Girls (2013), A Company Man (2012), A Christmas Tail (2014), Full of Grace (2015), Slap Her... She's French (2002), Slightly Single in L.A. (2013), Tangerines (2013), The Dirty Dozen: The Fatal Mission (1988), All Things Must Pass (2015), CIty of Joy (1992), Ernest in the Army (1998), Mythica: The Darkspore (2015), Santa Girl (2019), This Must Be the Place (2011), American Ninja 3: Blood Hunt (1989), Bob the Butler (2005), Everything or Nothing (2012), Happy Christmas (2014), More Dead than Alive (1969), Saving Christmas (2014), The King's Choice (2016), We'll Never Have Paris (2014), Dancer, Texas Pop.81 (1998), Mythica: The Necromancer (2015), Audrey Rose (1977), Going Overboard (1989), Nine (2009), Killing Hunther (2017), Stay Tuned (1992), The Last Five Years (2014), Just Let Go (2015), Elmer Gantry (1960), Elfette Saves Christmas (2019), Crooked Arrows, Attack (1956), Collision (2013), Living on One Dollar (2013), Jack and Jill vs. the World (2008), Unexpected (2015), Digimon Adventure tri. Part 3: Confession (2016), Glass Trap (2005), Infinity (1996), The First Great Train Robbery (1978), Bakery in Brooklyn (2016), Buried Treasure (2001), King Naresuan 1 (2007), A Perfect 14 (2018), Count Yorga, Vampire (1970), The Mod Squad (1999), The Wondeful Country (1969), 4th Man Out (2015), The Confirmation (2016), Cardboard Boxer (2016), Freeheld (2015), Chasers (1994), Ernest Rides Again (1993), Bob Marley: Roots of the Man (2018), Green Dragon (2001), Larry Gaye: Renegade Male Flight Attendant (2015), Miss Conception (2008), Making Babies (2018), Straight A's (2013), Who Gets the Dog? (2016), The Final Cut (2004), Vampire's Kiss (1988), Copying Beethoven (2006), Prince Avalanche (2013), Ned Kelly (1970), Parkland (2013), The Almost Perfect Bank Robbery (1999), The Jade Pendant (2017), Rosencrantz & Guildenstern Are Dead (1990), The Christmas Candle (2013), The Cokeville Miracle (2015), The Brass Teapot (2012), Z for Zachariah (2015), Another Mother's Son (2017), Atlas Shrugged: Part II (2012), The Return of Swamp Thing (1989), Touched (2005), Saint Ralph (2004), The Brothers Bloom (2008), Between Strangers (2002), Mr. Fix It (2006), Wind (1992), Brick Lane (2007), Oklahoma Crude (1973), That Sugar Film (2014), Trading Mom (1994), All We Had (2016), Retrograde (2004), Burning Bright (2010), Fun with Dick and Jane (1977), Robot & Frank (2012), Sarah's Key (2010), The Longest Week (2014), The Nugget (2002), The Perfect Family (2011), Living It Up (2000), Sky Line (2015), Mao's Last Dancer (2009), A Street Cat Named Bob (2016), The Concert (2009), Hanover Street (1979), The Bandit Hound (2016), Keep the Aspidistra Flying (1997), The Bad Mother’s Handbook (2007), Parts Per Billion (2014), The Mimic (2017), The Ticket (2016), Big Fish & Begonia (2016), Comeback Season (2006), Absolutely Anything (2015), King Naresuan 2 (2007), Hey Vern, Win $10,000…Or Just Count On Having Fun! (1987), Christmas in Hollywood (2014), Bad Ass (2012), Bottle Shock (2008), Cymbeline (2014), Danny Deckchair (2003), Why I Wore Lipstick to My Mastectomy (2006), All Forgotten (2001), Man Up (2015), Monster Island (2004), Priceless (2006), Remember the Daze (2007), The Last Keepers (2013), The Odyssey (2016), The Challenger Disaster (2019), Charm (2013), Bad Parents (2012), Another Harvest Moon (2010), Beauty (1998), Nobel Son (2007), Lobster War (2018), Beauty (1998), Dr. Otto And The Riddle Of The Gloom Beam (1986), From Nowhere (2016), Newlyweds (2011), The Russian Five (2018), Thank God It's Friday (1978), Hairbrained (2013), Passion Fish (1992), Lost and Found in Armenia (2012), Welcome to Happiness (2015), This Changes Everything (2015), The Drew: No Excuse, Just Produce (2016), Fear X (2003), Death of a Salesman (1985), The Competition (2018), The Wolfpack (2015), Food Stamped (2010), In Football We Trust (2015), Apple of My Eye (2017), Union Bound (2019), 10E (2019), Looking For Lola (1997), Blame (2017), The Bet (2016), Husband For Hire (2008), !0E (2019), Dirty (2005), The Bet (2016), Mazes and Monsters (1982), Broken English (2007), Local Boys (2002), Love & Saucers (2017), The Great Invisible (2014), When Did You Last See Your Father? (2007), Despite the Falling Snow (2016), Kingdom of Shadows (2015), Little Men (2016), Masterminds (1997), The Birdcatcher (2019), The Sapphires (2012), Misconception (2014), Dudes & Dragons (2015), Love & Saucers (2017), Police Story 2013 (2013), How Long Will I Love U (2018), The Boy Downstairs (2017), The Open Road (2009), Dead Snow 2: Red vs. Dead (2014), Ass Backwards (2013), Britney Spears: Workin' It (2014), Red Knot (2014), Jurassic City (2015), 91 Bullets in a Minute (2014), The Boy Downstairs (2017), Paper Heart (2009), 2:Hrs (2018), The Road Within (2014), Who Killed the Electric Car? (2006), Forever Strong (2008), Eloise (2017), Austin Found (2017), Dangerous Liaisons (2012), Song One (2014), Without Evidence (1995), Wolf Warrior (2015), Every Little Step (2008), The Little Traitor (2009), The Quiet (2005), Zeitgeist: Addendum (2008), The Boy Downstairs (2017), All the Queen's Horses (2017), Paradox (2017), Meet the Patels (2015), The Last 24 Hours: Jimi Hendrix (2019), Song for Marion (2012), Pretty Ugly People (2009), 50 Cent: Rap Star (2016), Miley Cyrus: Twerk It (2014), Sunshine Superman (2015), The Era of Vampires (2003), Shadow Dancer (2012), Selena Gomez: Living the Dream (2014), Slime Time (2019), Justin Timberlake: Suited Up (2014), Gang of Roses (2003), A Stand Up Guy (2016), Iris (2014), Message Man (2018), Newman (2015), The Extra Man (2010), Dolly Parton: Queen of Country (2015), Eminem: Behind the Lyrics (2013), Finding Altamira (2016), Girls vs Gangsters (2018), Carrie Underwood: Country Idol (2014), Charlie & Boots (2009), The Taking of Tiger Mountain (2014), Lamb (2015)

WHAT JUST LEFT:
Prescription Thugs (2015), Bigger Stronger Faster* (2008), Vanishing on 7th Street (2010), So Undercover (2012), The Alamo: Thirteen Days to Glory (1987), Stargate Origins: Catherine (2018), 12 Angry Men (1957), 1982 (2013), Duck, You Sucker (1971), A Most Wanted Man (2014), A View to a Kill (1985), Alien from L.A. (1988), Backtrack (2015), Bandits (2001), Barbershop 2: Back in Business (2004), Bloodsport (1988), Cattle Annie and Little Britches (1981), Cheech & Chong’s The Corsican Brothers (1984), Child's Play (1988), Citizenfour (2014), Coriolanus (2011), Dark Tide (2012), Diamonds Are Forever (1971), Dr. No (1962), Dragon Blade (2015), Earth Girls Are Easy (1988), Erik the Viking (1989), Fair Game (2010), Fargo (1996)

Omission issues documented in YouTube Forums.

Workflow for updating and maintenance (which will be reduced if only YouTube adds the feature to sort videos in playlists alphabetically):
1) Copy link of 'Free to watch' playlist.
2) Backup here. If not working, do it here.
3) Copy all titles from Excel/text file.
4) Alphabetise all the titles in the list.
5) Compare or diff the current and previous lists, and update this Letterboxd list accordingly.
6) Repeat steps 1 to 5 daily.