Undertale Text Box Generator

Building an Undertale Text Box Generator

I spent three weeks last year trying to get an Undertale-style dialogue system working in a browser. The end result was a text box generator that outputs HTML, CSS, and JavaScript all bundled together. It works fine for simple projects, but there are some headaches you won't find documented anywhere. The core of any Undertale text box generator comes down to three things: the box itself, the text rendering, and the typing animation. Most generators I've seen skip straight to a web form where you paste text and get a preview. That's fine for quick mockups, but it misses how the actual game handles line breaks, character counts, and dynamic resizing. Undertale's text boxes don't use fixed widths. The box resizes based on the longest line of text, then adds padding. Each line wraps at roughly 18-20 characters depending on the font. The "OK" button at the bottom only appears when the player has finished reading, which means you need to calculate when all the text has been fully typed out. This is where most generators fail.

I ran into this problem myself when building my version. The test case was a dialogue sequence with a mix of short two-word responses and one long paragraph. The generator I was using capped the box at a fixed height, which cut off the bottom of the long text. I had to write custom code that measures each line using canvas operations, finds the maximum width, then sets the box height accordingly. This usually adds about 45 minutes to the build time but saves you from broken layouts later.

Technical Details Most Guides Skip

The typing animation in Undertale isn't a simple CSS blink. Each character appears with a slight delay, and the delay varies based on punctuation. Periods and commas get a longer pause than other characters. This is noticeable if you've played the game, but implementing it requires a character-by-character approach rather than a blanket animation timer. My workaround was to create a timing map. Each punctuation mark gets a specific delay value, and regular characters get a default delay. The defaults are approximately 30 milliseconds per character for normal text, 80 milliseconds for periods, and 50 milliseconds for commas. This makes the text feel closer to the original game's rhythm without requiring frame-by-frame manual timing. Another issue is the "Skip" functionality. Undertale lets players skip the typing animation by pressing a key, which instantly shows all the text. Most generators don't implement this because it requires tracking whether the animation is still running and jumping to the end state. I solved this by keeping a reference to the current character index and allowing players to press Skip to set it equal to the total character count.

Common Pitfalls When Building Your Own

Font selection matters more than you'd think. Undertale uses a custom bitmap font, not a standard typeface. If you use a regular web font, the character widths won't match, and your line wrapping calculations will be off. I learned this the hard way when my generator produced boxes that looked correct on my screen but broke on mobile devices with different font rendering. The fix was to use a canvas-based approach instead of relying on DOM elements for text measurement. Canvas text rendering is consistent across browsers, and you can measure each line accurately before laying out the box. This adds complexity but eliminates the cross-browser inconsistencies that drive people crazy. Another pitfall is handling special characters. Undertale text boxes support color codes, sound cues, and special symbols. A basic generator might treat these as plain text, which breaks the layout. If you're building something for production use, you need to parse these codes and either render them or strip them before calculating dimensions.

I encountered this when a user submitted dialogue with embedded sound cues like [SN: bite]. My generator ignored the brackets and treated it as regular text, which made the line way too long. The solution was to write a simple parser that extracts these markers, counts them as zero width for layout purposes, but keeps them in the output so the final HTML still has the cues intact.

Downloading and Using Existing Solutions

If you don't want to build your own, there are a few Undertale Text Box Generator tools available online. Most are free, though some charge for commercial use. The quality varies significantly between them. I tested about six different generators before settling on one that worked well enough for my project. The ones I ended up rejecting had issues with responsive design, didn't handle line breaks properly, or required paid subscriptions for features that should be free. The one I kept costs nothing, exports clean code, and lets you customize colors and fonts. Here's what I'd look for when picking a generator: Does it handle dynamic resizing? Can you export code without watermarks? Does it support custom fonts? If the answer to any of these is no, keep looking.

When to Build Versus When to Use Existing Tools

Building your own Undertale text box generator makes sense if you need full control over the output, plan to integrate it into a larger project, or have specific requirements that existing tools don't meet. It takes time, roughly 20 to 40 hours depending on your experience level, but the result is yours to modify however you want. Using an existing generator is better if you need something quick, don't care about custom features, or are working on a personal project with no commercial goals. You can have a working prototype in under an hour using most tools, compared to days or weeks if you build from scratch. The tradeoff is flexibility versus speed. If you start with an existing generator and later need features it doesn't support, you'll either modify the source code or switch tools. I've seen people hit this wall when their project grew beyond the generator's capabilities, which is why I recommend understanding the underlying code even if you don't build everything yourself.

My advice is to download at least one generator and inspect its source code. Most are open source, and reading how other people solved these problems will save you time when you inevitably run into the same issues. I spent about three days just reading through other people's implementations before I felt confident building my own version.

Edge Cases That Will Catch You Off Guard

Emojis and wide characters break most generators. Undertale's font is monospaced in practice, meaning every character takes up the same width. Emojis and some Unicode characters aren't monospaced, which causes layout shifts that make the text box jump around unexpectedly. The workaround I found was to either filter out emojis before rendering or use a fallback font that handles them consistently. Neither solution is perfect, but they prevent the worst cases where your text box changes size mid-animation, which looks broken and confuses users. Another edge case is right-to-left text. Undertale doesn't support RTL languages natively, so most generators don't either. If you're working with Hebrew, Arabic, or other RTL scripts, you'll need to add direction flipping logic to the layout calculations. This is a significant amount of work and might be beyond what a simple generator can handle.

Audio synchronization is another feature the original game has that most generators lack. Undertale's text boxes play sounds as each line completes, which reinforces the pacing. Adding this requires integrating an audio library and mapping sound cues to text events, which increases complexity substantially.

Performance Considerations

If you're generating multiple text boxes on the same page, performance matters. Each generator instance creates DOM elements and event listeners, which add up if you have dozens of boxes. A page with 20 or more text boxes might start lagging on slower devices. I optimized my version by reusing a single canvas element and redrawing content instead of creating new elements for each box. This reduced memory usage significantly and made scrolling smoother. The tradeoff is that you can't interact with individual boxes independently, which is fine for static content but limiting if you need clickable elements. Another optimization is deferring animation until the box is visible. If you have a long dialogue sequence, pre-rendering all the text boxes wastes resources on content the user hasn't seen yet. Lazy loading solves this but requires more complex state management to track which boxes are active.

What I Wish I'd Known Before Starting

The biggest lesson is that Undertale's text box system is more complex than it appears. The simplicity of the visual design hides a lot of behind-the-scenes logic that handles resizing, timing, audio, and user input. Any generator that claims to replicate the experience perfectly is probably missing something. Another thing I wish I'd understood earlier is that community tools evolve quickly. The generator I used at the start of my project was outdated by the time I finished, missing features I hadn't even considered important yet. Keeping up with updates or maintaining your own fork is necessary if you rely on external tools for production work. Finally, document your decisions. I spent hours debugging issues that I could have avoided by writing down why I chose certain approaches. Notes about font choices, timing values, and layout calculations saved me from redoing work when I returned to the project after a break.

There's no single right way to build an Undertale Text Box Generator. The best approach depends on your goals, timeline, and technical comfort level. Just make sure you understand the limitations of whatever tool you choose, because the gap between "works fine in testing" and "works fine in production" is usually where these projects fall apart.