If you've ever tried to display a player's name and ended up with weird blocks, question marks, or garbled symbols, you probably need to start using roblox utf8 functions in your scripts. It's one of those things that most of us ignore when we first start scripting in Luau because, honestly, if you're just writing "Hello World," everything works fine. But the moment you start dealing with a global audience—which is basically every game on Roblox—the standard string library starts to fall apart.
The reality is that the internet isn't just made of the standard A-Z alphabet. Players are going to join your game with names containing accented letters, Cyrillic characters, Kanji, or just a mountain of emojis. If your code is still treating every single character as a single byte, you're going to run into some really annoying bugs that are surprisingly hard to track down if you don't know what you're looking for.
Why the standard string library isn't enough
In the old days of programming, everything was basically ASCII. One character equaled one byte. It was simple, but it was also very limited. Then came UTF-8, which is what Roblox uses. In UTF-8, a character can be anywhere from one to four bytes long. This is where the confusion starts for many developers.
When you use string.len(), it doesn't actually count the number of characters you see on the screen. It counts the number of bytes. If you have a string like "Apple," string.len will return 5, and everything is great. But if you have an emoji like "🍎", string.len might return 4. If you try to use string.sub to cut that emoji in half, you'll end up with a "malformed" string that looks like a broken box or a question mark.
This is exactly why the roblox utf8 library exists. it gives us the tools to handle these multi-byte characters without breaking our strings or crashing our UI elements.
Getting the real length of a string
The most common mistake I see is scripters using string.len to limit the length of a text box or a chat message. If you want to make sure a player's nickname is under 20 characters, using the standard library is a recipe for disaster. A player could put in five emojis, and suddenly your code thinks they've used 20 characters, even though it only looks like five on the screen.
To fix this, you've got to use utf8.len(). It's super straightforward. Instead of myString:len(), you just call utf8.len(myString). This function actually iterates through the string and counts the valid UTF-8 sequences.
However, there's a small catch you should know about. If utf8.len encounters a character it doesn't recognize or a sequence that's broken, it returns nil and the position of the broken character. So, it's always a good idea to wrap it in a check. You don't want your script to error out just because someone pasted a weird symbol into a text box.
Handling emojis and special symbols
Emojis are the biggest headache when it comes to text. Some emojis are actually multiple characters joined together by "invisible" connectors. While roblox utf8 helps a lot, it's worth remembering that text rendering is its own beast. But at the very least, using utf8.len ensures that you aren't accidentally cutting a character's data in half.
Slicing strings without breaking them
We've all been there: you want to create a "typewriter" effect where text appears one letter at a time. If you use string.sub, you're going to eventually hit a character that takes up more than one byte. When that happens, your typewriter effect will show a weird glitched symbol for a split second before the rest of the character loads. It looks unprofessional and buggy.
To do this properly, you need to find the byte offset of the characters. This is where utf8.offset comes in. It helps you find exactly where the n-th character starts in terms of bytes.
So, if you want the first three characters of a string, you don't just grab index 1 to 3. You use utf8.offset to find where the fourth character starts and then cut the string just before that point. It sounds a bit more complicated, and yeah, it's an extra step, but it's the only way to make sure your UI doesn't look like it's glitching out for international players.
Iterating through text with utf8.codes
If you ever need to loop through a string character by character—maybe you're building a custom chat filter or a fancy text animation—you should avoid the standard for i = 1, #str do loop. Instead, the roblox utf8 library provides utf8.codes.
Using utf8.codes is actually pretty cool. It works just like pairs or ipairs. It gives you the starting byte position and the numerical "code point" of each character.
lua for offset, codePoint in utf8.codes("Hello 🍎") do print("Character at", offset, "has code point", codePoint) end
This is much safer because it automatically jumps the correct number of bytes for each character. You don't have to manually calculate if the next character is one byte or four bytes; the library handles all that heavy lifting for you.
Why this matters for game localization
Roblox is pushing hard for localization. If you want your game to grow, you're eventually going to want to translate it into Spanish, Portuguese, French, or even Chinese and Korean. These languages are full of characters that will absolutely break a script that relies on old-school string methods.
By getting into the habit of using roblox utf8 now, you're essentially "future-proofing" your game. You won't have to go back and rewrite your entire UI system or chat logic when you decide to launch in another country. It's just good practice.
Imagine a player named "José." In standard ASCII/string methods, that 'é' might be treated as two bytes. If your code is set up to truncate names at 4 bytes, "José" might become "Jos" followed by a fragment of the 'é', which usually displays as an ugly "" symbol. It's a small detail, but those small details are what separate amateur games from the ones that feel polished and professional.
Common pitfalls to watch out for
Even though the roblox utf8 library is great, it's not magic. One thing it doesn't do is handle "grapheme clusters" perfectly. Some emojis (like flags or family emojis) are actually several code points combined. While utf8.len is much better than string.len, it might still count a complex emoji as two or three characters depending on how it's constructed.
For most Roblox games, this isn't a deal-breaker. But if you're making a game that's extremely heavy on text manipulation—like a word puzzle game or a deep social simulator—you might need to look even deeper into how Luau handles text.
Another thing to remember is performance. While roblox utf8 is fast, it is slightly slower than the basic string library because it has to do more work to validate the characters. For 99% of use cases, you'll never notice the difference. But if you're trying to process a 50,000-character string every single frame (which, let's be real, you shouldn't be doing anyway), you might want to be mindful of how often you're calling these functions.
Wrapping it up
At the end of the day, using roblox utf8 is just about being a better developer. It's about making sure your game is inclusive and works for everyone, regardless of what language they speak or what characters they use in their username.
It might feel a bit tedious to swap out your familiar string.sub and string.len calls for their UTF-8 counterparts, but once you get the hang of it, it becomes second nature. Your UI will look better, your chat will be more stable, and you'll avoid those "invisible" bugs that only seem to happen to players in other countries. So, the next time you're working on a text-heavy feature, definitely give the utf8 library the attention it deserves.