Bubble letters put each character inside a circle or a box. They look playful, they stand out in a plain-text feed, and they work well as decoration for short words: Ⓗⓔⓛⓛⓞ. That is the first style the generator makes from whatever you type.
You get four at once. Bubble letters are outlined circles, filled bubbles are the solid, dark-circle version, square bubbles put capitals in outlined boxes, and filled squares have solid squares with reversed letters. Click copy beside the one you want.
Details of each style
The outlined circle set has both capitals and lowercase letters, and it is the only one of the four with digits: ① to ⑨, and ⓪. Use it if you need numbers in the text.
The filled circles and both square styles come as capital letters only. A lowercase word is converted to capitals in those, as there is no lowercase version of those symbols. Digits are left as plain numbers beside them.
Spaces and punctuation are not changed, which means word gaps will look as they do in normal text.
Why some symbols look different on your phone
A few of the filled squares, in particular the squared A, B, O and P, are also treated as emoji by phones and some apps. On those devices, they may display in bright colour, with a rounded blue or red look, instead of the plain black version you see in the tool. That is down to the device, not to the text. If the colour version is not what you want, try the circle styles instead, which are not affected.
Very old software may not have a font with these shapes and will show empty boxes. Test on the platform where you will use it.
Where bubbles work
Bios and captions on social media, chat messages, event posters made in apps that take plain text, school and club notices, and game names. For headings, they are best at three or four words. Long passages in bubbles are hard to read, since each letter takes up much more space than normal and the eye has to jump around.
As with other Unicode styles, there are two things to remember. Screen readers often read these characters one by one as symbols, such as “circled latin small letter h”, which can be hard for blind readers to follow. And search will not match them to normal letters. Keep key words in plain text.
For a giant block-letter effect instead of a decorated one, the big text generator is the one. The wide text generator spreads letters out, and the fancy text generator shows more than twenty looks. For the technical background, see how fancy text fonts work.