Introduction
Since its release in 2015, Undertale has inspired one of the most passionate and creative communities in gaming. With its quirky humour, deep moral choices, and iconic characters like Sans and Papyrus, it’s no wonder that thousands of fans have created their own Undertale fan games.
Whether you’re hunting for a new boss rush challenge, emotional storytelling, or alternate universe (AU) experiences, the fan game scene is thriving in 2025. This guide brings you the best Undertale fan games to download or play online, with options for casual players and hardcore fans alike.
Let’s dive into a world where determination never fades.
What Are Undertale Fan Games?
Undertale fan games are unofficial projects made by fans using the lore, characters, and mechanics of Undertale — often adding new twists, stories, or battle systems. Some are built from scratch, while others modify the original game using engines like GameMaker Studio or RPG Maker.
These games range from:
- Serious narrative-driven experiences (like Dusttale)
- AU crossovers (like Underfell or Outertale)
- Pure combat simulators (like Bad Time Simulator)
Fan games allow players to reimagine the Undertale universe — sometimes dark, sometimes funny, always creative.
Why Undertale Fan Games Still Matter in 2025
In 2025, interest in Undertale fan games hasn’t just survived — it’s exploded again thanks to platforms like itch.io and Game Jolt, plus the rise of SGE (Search Generative Experience), which helps users discover hidden indie gems more easily.
Here’s why these games matter:
- They keep the spirit of Undertale alive.
- They let fans experiment with “what if?” scenarios.
- They often showcase incredible indie dev talent.
Many developers who started with Undertale mods have gone on to release full indie titles of their own.
Best Undertale Fan Games to Play in 2025
Below are the must-play Undertale fan games, whether you’re into alternate universes, epic battles, or emotional storytelling.
Dusttale
Concept: A darker version of Undertale where Sans takes justice into his own hands.
Why It’s Popular: It explores the emotional weight of choices made in the Genocide route. Players face a powerful and broken Sans, haunted by loss and guilt.
Standout Features:
- Gripping AU narrative
- Intense boss fights
- Multiple endings
LSI Keywords: Dusttale download, Genocide AU, Undertale AU mods
Undertale Yellow
Concept: A prequel fan game featuring a new protagonist, Clover.
Why It’s Popular: With Toby Fox’s blessing, Undertale Yellow offers an original story, fresh puzzles, and amazing pixel art that fits perfectly into the existing universe.
Standout Features:
- Original overworld and characters
- Gaster Blaster-style mechanics
- Thoughtful writing and music
LSI Keywords: Undertale Yellow full version, prequel fan game, Undertale lore
Last Breath (Sans Fight)
Concept: A brutal Sans battle taken to its extreme — and beyond.
Why It’s Popular: Last Breath is known for its multi-phase boss fight and shocking transformations. It’s like Undertale meets Dragon Ball Z in its intensity.
Standout Features:
- Phase-based difficulty progression
- Custom sprites and music
- AU deep lore for Sans fans
LSI Keywords: Last Breath Phase 3, Sans AU fights, hard Undertale fan games
XTale / Underverse
Concept: A crossover of multiple AUs in a web-animated story and combat simulator.
Why It’s Popular: Created by Jakei, XTale combines original storytelling with dramatic AU clashes in an anime-style presentation. Underverse is the fan animation tie-in.
Standout Features:
- Battle simulations between AU versions
- Rich lore and unique characters (like Cross!Sans)
- Available as both a game and a web series
LSI Keywords: XTale game download, Cross-Sans fight, Underverse AU
Bad Time Simulator
Concept: A web-based recreation of the Sans Genocide fight.
Why It’s Popular: This game is perfect for those who want the thrill of Sans’ boss fight without replaying the full game.
Standout Features:
- Browser-based (no download!)
- Practice mode and difficulty scaling
- Classic Undertale art and music
LSI Keywords: play Bad Time Simulator online, Sans boss fight, no download Undertale
Underswap
Concept: A role-reversed AU where characters swap personalities and roles (Sans is now Papyrus and vice versa).
Why It’s Popular: Undertale Underswap delivers a fun, lighthearted twist while maintaining Undertale’s core themes. The art is often colourful and playful.
Standout Features:
- Charming redesigns of familiar faces
- Wholesome vibe with replayability
- Popular among cosplayers and artists
LSI Keywords: Underswap demo, swap AU, Papyrus as Sans
7. Inverted Fate
Concept: An ambitious fan game where almost every character’s story path is changed.
Why It’s Popular: It offers a complete reimagining of the game while still honouring its structure. Inverted Fate includes new locations, music, and even custom mechanics.
Standout Features:
- Full game-length experience
- New soundtrack and battles
- Massive community contributions
LSI Keywords: Inverted Fate Undertale, full fan game download, alternate timeline AU
Where to Find and Download Undertale Fan Games
| Platform | Best For | Website |
| itch.io | Indie AU games, demos | |
| Game Jolt | Popular boss fights, simulators | |
| Fan updates, discussions | r/Undertale | |
| YouTube | Gameplay previews, trailers | YouTube Gaming |
Tip: Always download from official creator pages to avoid malware or broken files. Many fan games are free, but donations help developers keep creating!
What Makes a Good Undertale Fan Game?
A great Undertale fan game nails three things:
Originality with respect: New stories or gameplay that still feel like Undertale.
Polished gameplay: Smooth battles, working mechanics, and custom content.
Emotional depth: Just like the original, it should make you feel something.
Pro Tip: If the game doesn’t have original music, it’s likely a mod, not a standalone fan game.
Is It Legal to Play or Make Undertale Fan Games?
Yes — if they’re non-commercial. Toby Fox has supported fan projects as long as they don’t profit from Undertale’s IP. That means:
Free games with credits are okay
Paid fan games or merch sales are not
If you’re a developer, always give credit and avoid monetisation unless you get official approval.
Read Also: Rocksteady Games: Timeline, Top Titles & What’s Coming Next
Conclusion
If you thought Undertale was a one-time experience, think again. In 2025, the world of Undertale fan games is bigger, bolder, and more creative than ever. From serious AU drama in Dusttale to fun battle sims like Bad Time Simulator, there’s something for every type of fan.
Whether you’re new to the Underground or a seasoned Soul collector, there’s always a new journey waiting. So grab your keyboard, choose your route, and stay determined.
FAQs
What is the most popular Undertale fan game?
Dusttale and Last Breath are among the most popular due to their dramatic storylines and challenging Sans fights.
Are Undertale fan games free?
Yes, most are completely free to download and play. Donations are often optional.
Can I play Undertale fan games on mobile?
Some web-based fan games (like Bad Time Simulator) work on mobile browsers. Most full games require a PC.
Are fan games canon?
No. Undertale fan games are non-canonical alternate universes or “what if” stories created by the community.
Is it safe to download fan games?
Yes, if downloaded from trusted sites like itch.io or Game Jolt. Avoid unofficial links or sketchy downloads.
