Undertale Yellow is the strongest fit if you want a substantial, completed prequel; TS!UNDERSWAP offers a sizeable but unfinished role-swap; Project Spacetime Outertale reimagines Undertale with a space theme; and IF – Underswap is a completed browser-playable interactive story. They suit different tastes, so there is no single objective winner.
Which Undertale fan game should you play?
Use completion status and format as your first filters. If you want a full-length RPG-style prequel, start with Undertale Yellow. If you are happy to play an in-development project, try TS!UNDERSWAP. For an alternate-universe story with a space setting, consider Project Spacetime Outertale. If you would rather play in a browser than download a conventional RPG, IF – Underswap is the clearest match.
| # | Preview | Product | Price | |
|---|---|---|---|---|
| 1 |
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8-4 Fangamer Undertale RPG NINTENDO SWITCH JAPANESE IMPORT REGION FREE | $43.88 | Buy on Amazon |
| 2 |
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Untitled Goose Game - Nintendo Switch | $23.29 | Buy on Amazon |
| Game | Best fit | Status and scope | Format and platforms |
|---|---|---|---|
| Undertale Yellow | A substantial prequel | Full-length fan-made prequel; three main routes | Download for Windows; the creators host it through Game Jolt and IndieDB. The creators say the planned Mac port did not proceed. |
| TS!UNDERSWAP | A sizeable ongoing role-swap project | In development; current build covers Ruined Home and Starlight Isles, with a first run estimated by the creators at 4–6 hours | Windows, macOS, Linux, and Android |
| Project Spacetime Outertale | A space-themed alternate universe | A take on Outertale; the page distinguishes a community-authored 5.10 build from the official 5.04 release | Windows, Mac, Linux, Android, browser, and iOS through the web version, according to the Game Jolt page |
| IF – Underswap | A completed browser story | Story labeled complete; routes, puzzles, mazes, and boss fights | HTML5 browser experience |
Undertale Yellow: a completed prequel
Team Undertale Yellow describes its game as a full-length fan-made prequel following Clover, with new areas, characters, music, and puzzles. Its three main routes make it the most straightforward pick here for someone looking for a large, self-contained Undertale-adjacent adventure.
The team recommends playing the original Undertale first: its game page warns that Yellow contains spoilers and is slightly more difficult. It also lists options including reduced screen shake, autofire, easy mode, and auto-rhythm, plus XInput gamepad support. The page lists version 1.3.1; that version number should not be treated as confirmation of the latest build without checking the official page.
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For safe downloads, use the hosts linked by the creators. Team Undertale Yellow warns that other download sources are unofficial and could be dangerous. The team says its planned Mac port did not proceed and it was not then working on an OSX port, so check the official page for any later platform changes.
TS!UNDERSWAP: a large project still in development
Team Switched calls TS!UNDERSWAP an unofficial fan-made reimagining of Toby Fox’s Undertale. It swaps roles and builds its own take on the setting rather than serving as a direct continuation. The current build features Ruined Home and Starlight Isles; the creators estimate at least 4–6 hours for a first run and label the project in development.
The game page describes new areas and characters, reimagined enemies and bullet patterns, player-choice routes, puzzles, mobility mechanics, a journal, collectibles, and original art and music. It lists Windows, macOS, Linux, and Android. The page lists version 2.1.2 updates dated June 17, 2026 for Windows, Mac, and Android, and July 3, 2026 for Linux; check the page for the current build and platform-specific details.
Input and accessibility options listed by Team Switched include keyboard, Xbox and PlayStation controllers, general gamepads, and touchscreen controls, as well as subtitles, configurable controls, color-blind-friendly options, and an interactive tutorial.
Project Spacetime Outertale: Undertale in a space setting
Spacey presents Project Spacetime as a free take on Outertale, an Undertale alternate universe, with the stated aim “to experience UNDERTALE for the first time again.” That is the creator’s description of the project, not an independent assessment. Choose it if the alternate-universe premise and space theme appeal more than a close prequel or role-swap.
Pay attention to the version distinction on the Game Jolt page: it describes version 5.10 as a community-authored release and directs readers seeking the official 5.04 release to the project’s itch.io page. Do not assume those builds are interchangeable. The page lists Windows, Mac, Linux, Android, browser play, and iOS through the web version, and includes controller, save-file, and modding guidance. Check the project page for current releases and links before downloading.
Rank #2
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IF – Underswap: a completed interactive story in your browser
Darkpetal16 labels IF – Underswap’s story complete and lists it as an HTML5 project, so it is a browser-playable interactive-fiction experience rather than a conventional downloadable RPG. You play as a customizable Chara who falls into a monster kingdom beneath Lake Ebott. Its routes, relationship-focused story paths, mazes, puzzles, and boss fights make it a different kind of Undertale fan game from the other picks.
The project page credits Darkpetal16 as writer and programmer and credits the Underswap alternate universe to Popcorn Pr1nce.
How to find more Undertale fan games
A user-curated itch.io collection can help uncover projects in different formats, including short fan games, browser and action experiences, alternate-universe stories, and interactive fiction. Treat it as a discovery list, not a quality or completion ranking: those details vary by project and should be checked on each creator’s page.
Community discussions also bring up names such as Deltatraveler and PS!Outertale, but opinions about quality and completion differ. For any project beyond the four featured here, confirm its current status and supported platforms on an official creator page rather than relying on a comment or list entry.
Do you need to play Undertale first?
Undertale Yellow’s creators specifically recommend familiarity with the original and warn that their game contains spoilers. That makes playing Undertale first the safer order if you want to avoid story revelations. It is not a requirement to buy the original to access the fan games listed here; the featured pages describe free downloads or browser experiences. These projects are fan works, not physical editions of Undertale.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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